Alamofire: Elegant Networking in Swift

Alamofire is an HTTP networking library written in Swift.

Features

  • [x] Chainable Request / Response methods
  • [x] URL / JSON / plist Parameter Encoding
  • [x] Upload File / Data / Stream / MultipartFormData
  • [x] Download using Request or Resume data
  • [x] Authentication with NSURLCredential
  • [x] HTTP Response Validation
  • [x] TLS Certificate and Public Key Pinning
  • [x] Progress Closure & NSProgress
  • [x] cURL Debug Output
  • [x] Comprehensive Unit Test Coverage
  • [x] Complete Documentation

Component Libraries

In order to keep Alamofire focused specifically on core networking implementations, additional component libraries have been created by the Alamofire Software Foundation to bring additional functionality to the Alamofire ecosystem.

  • AlamofireImage - An image library including image response serializers, UIImage and UIImageView extensions, custom image filters, an auto-purging in-memory cache and a priority-based image downloading system.
  • AlamofireNetworkActivityIndicator - Controls the visibility of the network activity indicator on iOS using Alamofire. It contains configurable delay timers to help mitigate flicker and can support NSURLSession instances not managed by Alamofire.

Requirements

  • iOS 8.0+ / Mac OS X 10.9+ / tvOS 9.0+ / watchOS 2.0+
  • Xcode 7.3+

Migration Guides

Communication

  • If you need help, use Stack Overflow. (Tag ‘alamofire’)
  • If you’d like to ask a general question, use Stack Overflow.
  • If you found a bug, open an issue.
  • If you have a feature request, open an issue.
  • If you want to contribute, submit a pull request.

Installation

Embedded frameworks require a minimum deployment target of iOS 8 or OS X Mavericks (10.9).

Alamofire is no longer supported on iOS 7 due to the lack of support for frameworks. Without frameworks, running Travis-CI against iOS 7 would require a second duplicated test target. The separate test suite would need to import all the Swift files and the tests would need to be duplicated and re-written. This split would be too difficult to maintain to ensure the highest possible quality of the Alamofire ecosystem.

Manually

If you prefer not to use either of the aforementioned dependency managers, you can integrate Alamofire into your project manually.

Embedded Framework

  • Open up Terminal, cd into your top-level project directory, and run the following command “if” your project is not initialized as a git repository:
$ git init
  • Add Alamofire as a git submodule by running the following command:
$ git submodule add https://github.com/Alamofire/Alamofire.git
  • Open the new Alamofire folder, and drag the Alamofire.xcodeproj into the Project Navigator of your application’s Xcode project.

    It should appear nested underneath your application’s blue project icon. Whether it is above or below all the other Xcode groups does not matter.

  • Select the Alamofire.xcodeproj in the Project Navigator and verify the deployment target matches that of your application target.

  • Next, select your application project in the Project Navigator (blue project icon) to navigate to the target configuration window and select the application target under the “Targets” heading in the sidebar.
  • In the tab bar at the top of that window, open the “General” panel.
  • Click on the + button under the “Embedded Binaries” section.
  • You will see two different Alamofire.xcodeproj folders each with two different versions of the Alamofire.framework nested inside a Products folder.

    It does not matter which Products folder you choose from, but it does matter whether you choose the top or bottom Alamofire.framework.

  • Select the top Alamofire.framework for iOS and the bottom one for OS X.

    You can verify which one you selected by inspecting the build log for your project. The build target for Alamofire will be listed as either Alamofire iOS or Alamofire OSX.

  • And that’s it!

The Alamofire.framework is automagically added as a target dependency, linked framework and embedded framework in a copy files build phase which is all you need to build on the simulator and a device.


Usage

Making a Request

import Alamofire

Alamofire.request(.GET, "https://httpbin.org/get")

Response Handling

Alamofire.request(.GET, "https://httpbin.org/get", parameters: ["foo": "bar"])
         .responseJSON { response in
             print(response.request)  // original URL request
             print(response.response) // URL response
             print(response.data)     // server data
             print(response.result)   // result of response serialization

             if let JSON = response.result.value {
                 print("JSON: \(JSON)")
             }
         }

Networking in Alamofire is done asynchronously. Asynchronous programming may be a source of frustration to programmers unfamiliar with the concept, but there are very good reasons for doing it this way.

Rather than blocking execution to wait for a response from the server, a callback is specified to handle the response once it’s received. The result of a request is only available inside the scope of a response handler. Any execution contingent on the response or data received from the server must be done within a handler.

Validation

By default, Alamofire treats any completed request to be successful, regardless of the content of the response. Calling validate before a response handler causes an error to be generated if the response had an unacceptable status code or MIME type.

Manual Validation

Alamofire.request(.GET, "https://httpbin.org/get", parameters: ["foo": "bar"])
         .validate(statusCode: 200..<300)
         .validate(contentType: ["application/json"])
         .response { response in
             print(response)
         }

Automatic Validation

Automatically validates status code within 200...299 range, and that the Content-Type header of the response matches the Accept header of the request, if one is provided.

Alamofire.request(.GET, "https://httpbin.org/get", parameters: ["foo": "bar"])
         .validate()
         .responseJSON { response in
             switch response.result {
             case .Success:
                 print("Validation Successful")
             case .Failure(let error):
                 print(error)
             }
         }

Response Serialization

Built-in Response Methods

  • response()
  • responseData()
  • responseString(encoding: NSStringEncoding)
  • responseJSON(options: NSJSONReadingOptions)
  • responsePropertyList(options: NSPropertyListReadOptions)

Response Handler

Alamofire.request(.GET, "https://httpbin.org/get", parameters: ["foo": "bar"])
         .validate()
         .response { request, response, data, error in
             print(request)
             print(response)
             print(data)
             print(error)
          }

The response serializer does NOT evaluate any of the response data. It merely forwards on all the information directly from the URL session delegate. We strongly encourage you to leverage the other response serializers taking advantage of Response and Result types.

Response Data Handler

Alamofire.request(.GET, "https://httpbin.org/get", parameters: ["foo": "bar"])
         .validate()
         .responseData { response in
             print(response.request)
             print(response.response)
             print(response.result)
          }

Response String Handler

Alamofire.request(.GET, "https://httpbin.org/get")
         .validate()
         .responseString { response in
             print("Success: \(response.result.isSuccess)")
             print("Response String: \(response.result.value)")
         }

Response JSON Handler

Alamofire.request(.GET, "https://httpbin.org/get")
         .validate()
         .responseJSON { response in
             debugPrint(response)
         }

Chained Response Handlers

Response handlers can even be chained:

Alamofire.request(.GET, "https://httpbin.org/get")
         .validate()
         .responseString { response in
             print("Response String: \(response.result.value)")
         }
         .responseJSON { response in
             print("Response JSON: \(response.result.value)")
         }

HTTP Methods

Alamofire.Method lists the HTTP methods defined in RFC 7231 §4.3:

public enum Method: String {
    case OPTIONS, GET, HEAD, POST, PUT, PATCH, DELETE, TRACE, CONNECT
}

These values can be passed as the first argument of the Alamofire.request method:

Alamofire.request(.POST, "https://httpbin.org/post")

Alamofire.request(.PUT, "https://httpbin.org/put")

Alamofire.request(.DELETE, "https://httpbin.org/delete")

Parameters

GET Request With URL-Encoded Parameters

Alamofire.request(.GET, "https://httpbin.org/get", parameters: ["foo": "bar"])
// https://httpbin.org/get?foo=bar

POST Request With URL-Encoded Parameters

let parameters = [
    "foo": "bar",
    "baz": ["a", 1],
    "qux": [
        "x": 1,
        "y": 2,
        "z": 3
    ]
]

Alamofire.request(.POST, "https://httpbin.org/post", parameters: parameters)
// HTTP body: foo=bar&baz[]=a&baz[]=1&qux[x]=1&qux[y]=2&qux[z]=3

Parameter Encoding

Parameters can also be encoded as JSON, Property List, or any custom format, using the ParameterEncoding enum:

enum ParameterEncoding {
    case URL
    case URLEncodedInURL
    case JSON
    case PropertyList(format: NSPropertyListFormat, options: NSPropertyListWriteOptions)
    case Custom((URLRequestConvertible, [String: AnyObject]?) -> (NSMutableURLRequest, NSError?))

    func encode(request: NSURLRequest, parameters: [String: AnyObject]?) -> (NSURLRequest, NSError?)
    { ... }
}
  • URL: A query string to be set as or appended to any existing URL query for GET, HEAD, and DELETE requests, or set as the body for requests with any other HTTP method. The Content-Type HTTP header field of an encoded request with HTTP body is set to application/x-www-form-urlencoded. Since there is no published specification for how to encode collection types, Alamofire follows the convention of appending [] to the key for array values (foo[]=1&foo[]=2), and appending the key surrounded by square brackets for nested dictionary values (foo[bar]=baz).
  • URLEncodedInURL: Creates query string to be set as or appended to any existing URL query. Uses the same implementation as the .URL case, but always applies the encoded result to the URL.
  • JSON: Uses NSJSONSerialization to create a JSON representation of the parameters object, which is set as the body of the request. The Content-Type HTTP header field of an encoded request is set to application/json.
  • PropertyList: Uses NSPropertyListSerialization to create a plist representation of the parameters object, according to the associated format and write options values, which is set as the body of the request. The Content-Type HTTP header field of an encoded request is set to application/x-plist.
  • Custom: Uses the associated closure value to construct a new request given an existing request and parameters.

Manual Parameter Encoding of an NSURLRequest

let URL = NSURL(string: "https://httpbin.org/get")!
var request = NSMutableURLRequest(URL: URL)

let parameters = ["foo": "bar"]
let encoding = Alamofire.ParameterEncoding.URL
(request, _) = encoding.encode(request, parameters: parameters)

POST Request with JSON-encoded Parameters

let parameters = [
    "foo": [1,2,3],
    "bar": [
        "baz": "qux"
    ]
]

Alamofire.request(.POST, "https://httpbin.org/post", parameters: parameters, encoding: .JSON)
// HTTP body: {"foo": [1, 2, 3], "bar": {"baz": "qux"}}

HTTP Headers

Adding a custom HTTP header to a Request is supported directly in the global request method. This makes it easy to attach HTTP headers to a Request that can be constantly changing.

For HTTP headers that do not change, it is recommended to set them on the NSURLSessionConfiguration so they are automatically applied to any NSURLSessionTask created by the underlying NSURLSession.

let headers = [
    "Authorization": "Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==",
    "Accept": "application/json"
]

Alamofire.request(.GET, "https://httpbin.org/get", headers: headers)
         .responseJSON { response in
             debugPrint(response)
         }

Caching

Caching is handled on the system framework level by NSURLCache.

Uploading

Supported Upload Types

  • File
  • Data
  • Stream
  • MultipartFormData

Uploading a File

let fileURL = NSBundle.mainBundle().URLForResource("Default", withExtension: "png")
Alamofire.upload(.POST, "https://httpbin.org/post", file: fileURL)

Uploading with Progress

Alamofire.upload(.POST, "https://httpbin.org/post", file: fileURL)
         .progress { bytesWritten, totalBytesWritten, totalBytesExpectedToWrite in
             print(totalBytesWritten)

             // This closure is NOT called on the main queue for performance
             // reasons. To update your ui, dispatch to the main queue.
             dispatch_async(dispatch_get_main_queue()) {
                 print("Total bytes written on main queue: \(totalBytesWritten)")
             }
         }
         .validate()
         .responseJSON { response in
             debugPrint(response)
         }

Uploading MultipartFormData

Alamofire.upload(
    .POST,
    "https://httpbin.org/post",
    multipartFormData: { multipartFormData in
        multipartFormData.appendBodyPart(fileURL: unicornImageURL, name: "unicorn")
        multipartFormData.appendBodyPart(fileURL: rainbowImageURL, name: "rainbow")
    },
    encodingCompletion: { encodingResult in
        switch encodingResult {
        case .Success(let upload, _, _):
            upload.responseJSON { response in
                debugPrint(response)
            }
        case .Failure(let encodingError):
            print(encodingError)
        }
    }
)

Downloading

Supported Download Types

  • Request
  • Resume Data

Downloading a File

Alamofire.download(.GET, "https://httpbin.org/stream/100") { temporaryURL, response in
    let fileManager = NSFileManager.defaultManager()
    let directoryURL = fileManager.URLsForDirectory(.DocumentDirectory, inDomains: .UserDomainMask)[0]
    let pathComponent = response.suggestedFilename

    return directoryURL.URLByAppendingPathComponent(pathComponent!)
}

Using the Default Download Destination

let destination = Alamofire.Request.suggestedDownloadDestination(directory: .DocumentDirectory, domain: .UserDomainMask)
Alamofire.download(.GET, "https://httpbin.org/stream/100", destination: destination)

Downloading a File w/Progress

Alamofire.download(.GET, "https://httpbin.org/stream/100", destination: destination)
         .progress { bytesRead, totalBytesRead, totalBytesExpectedToRead in
             print(totalBytesRead)

             // This closure is NOT called on the main queue for performance
             // reasons. To update your ui, dispatch to the main queue.
             dispatch_async(dispatch_get_main_queue()) {
                 print("Total bytes read on main queue: \(totalBytesRead)")
             }
         }
         .response { _, _, _, error in
             if let error = error {
                 print("Failed with error: \(error)")
             } else {
                 print("Downloaded file successfully")
             }
         }

Accessing Resume Data for Failed Downloads

Alamofire.download(.GET, "https://httpbin.org/stream/100", destination: destination)
         .response { _, _, data, _ in
             if let
                 data = data,
                 resumeDataString = NSString(data: data, encoding: NSUTF8StringEncoding)
             {
                 print("Resume Data: \(resumeDataString)")
             } else {
                 print("Resume Data was empty")
             }
         }

The data parameter is automatically populated with the resumeData if available.

let download = Alamofire.download(.GET, "https://httpbin.org/stream/100", destination: destination)
download.response { _, _, _, _ in
    if let
        resumeData = download.resumeData,
        resumeDataString = NSString(data: resumeData, encoding: NSUTF8StringEncoding)
    {
        print("Resume Data: \(resumeDataString)")
    } else {
        print("Resume Data was empty")
    }
}

Authentication

Authentication is handled on the system framework level by NSURLCredential and NSURLAuthenticationChallenge.

Supported Authentication Schemes

HTTP Basic Authentication

The authenticate method on a Request will automatically provide an NSURLCredential to an NSURLAuthenticationChallenge when appropriate:

let user = "user"
let password = "password"

Alamofire.request(.GET, "https://httpbin.org/basic-auth/\(user)/\(password)")
         .authenticate(user: user, password: password)
         .responseJSON { response in
             debugPrint(response)
         }

Depending upon your server implementation, an Authorization header may also be appropriate:

let user = "user"
let password = "password"

let credentialData = "\(user):\(password)".dataUsingEncoding(NSUTF8StringEncoding)!
let base64Credentials = credentialData.base64EncodedStringWithOptions([])

let headers = ["Authorization": "Basic \(base64Credentials)"]

Alamofire.request(.GET, "https://httpbin.org/basic-auth/user/password", headers: headers)
         .responseJSON { response in
             debugPrint(response)
         }

Authentication with NSURLCredential

let user = "user"
let password = "password"

let credential = NSURLCredential(user: user, password: password, persistence: .ForSession)

Alamofire.request(.GET, "https://httpbin.org/basic-auth/\(user)/\(password)")
         .authenticate(usingCredential: credential)
         .responseJSON { response in
             debugPrint(response)
         }

Timeline

Alamofire collects timings throughout the lifecycle of a Request and creates a Timeline object exposed as a property on a Response.

Alamofire.request(.GET, "https://httpbin.org/get", parameters: ["foo": "bar"])
         .validate()
         .responseJSON { response in
             print(response.timeline)
         }

The above reports the following Timeline info:

  • Latency: 0.428 seconds
  • Request Duration: 0.428 seconds
  • Serialization Duration: 0.001 seconds
  • Total Duration: 0.429 seconds

Printable

let request = Alamofire.request(.GET, "https://httpbin.org/ip")

print(request)
// GET https://httpbin.org/ip (200)

DebugPrintable

let request = Alamofire.request(.GET, "https://httpbin.org/get", parameters: ["foo": "bar"])

debugPrint(request)

Output (cURL)

$ curl -i \
    -H "User-Agent: Alamofire" \
    -H "Accept-Encoding: Accept-Encoding: gzip;q=1.0,compress;q=0.5" \
    -H "Accept-Language: en;q=1.0,fr;q=0.9,de;q=0.8,zh-Hans;q=0.7,zh-Hant;q=0.6,ja;q=0.5" \
    "https://httpbin.org/get?foo=bar"


Advanced Usage

Alamofire is built on NSURLSession and the Foundation URL Loading System. To make the most of this framework, it is recommended that you be familiar with the concepts and capabilities of the underlying networking stack.

Recommended Reading

Manager

Top-level convenience methods like Alamofire.request use a shared instance of Alamofire.Manager, which is configured with the default NSURLSessionConfiguration.

As such, the following two statements are equivalent:

Alamofire.request(.GET, "https://httpbin.org/get")
let manager = Alamofire.Manager.sharedInstance
manager.request(NSURLRequest(URL: NSURL(string: "https://httpbin.org/get")!))

Applications can create managers for background and ephemeral sessions, as well as new managers that customize the default session configuration, such as for default headers (HTTPAdditionalHeaders) or timeout interval (timeoutIntervalForRequest).

Creating a Manager with Default Configuration

let configuration = NSURLSessionConfiguration.defaultSessionConfiguration()
let manager = Alamofire.Manager(configuration: configuration)

Creating a Manager with Background Configuration

let configuration = NSURLSessionConfiguration.backgroundSessionConfigurationWithIdentifier("com.example.app.background")
let manager = Alamofire.Manager(configuration: configuration)

Creating a Manager with Ephemeral Configuration

let configuration = NSURLSessionConfiguration.ephemeralSessionConfiguration()
let manager = Alamofire.Manager(configuration: configuration)

Modifying Session Configuration

var defaultHeaders = Alamofire.Manager.sharedInstance.session.configuration.HTTPAdditionalHeaders ?? [:]
defaultHeaders["DNT"] = "1 (Do Not Track Enabled)"

let configuration = NSURLSessionConfiguration.defaultSessionConfiguration()
configuration.HTTPAdditionalHeaders = defaultHeaders

let manager = Alamofire.Manager(configuration: configuration)

This is not recommended for Authorization or Content-Type headers. Instead, use URLRequestConvertible and ParameterEncoding, respectively.

Request

The result of a request, upload, or download method is an instance of Alamofire.Request. A request is always created using a constructor method from an owning manager, and never initialized directly.

Methods like authenticate, validate and responseData return the caller in order to facilitate chaining.

Requests can be suspended, resumed, and cancelled:

  • suspend(): Suspends the underlying task and dispatch queue
  • resume(): Resumes the underlying task and dispatch queue. If the owning manager does not have startRequestsImmediately set to true, the request must call resume() in order to start.
  • cancel(): Cancels the underlying task, producing an error that is passed to any registered response handlers.

Response Serialization

Creating a Custom Response Serializer

Alamofire provides built-in response serialization for strings, JSON, and property lists, but others can be added in extensions on Alamofire.Request.

For example, here’s how a response handler using Ono might be implemented:

extension Request {
    public static func XMLResponseSerializer() -> ResponseSerializer<ONOXMLDocument, NSError> {
        return ResponseSerializer { request, response, data, error in
            guard error == nil else { return .Failure(error!) }

            guard let validData = data else {
                let failureReason = "Data could not be serialized. Input data was nil."
                let error = Error.errorWithCode(.DataSerializationFailed, failureReason: failureReason)
                return .Failure(error)
            }

            do {
                let XML = try ONOXMLDocument(data: validData)
                return .Success(XML)
            } catch {
                return .Failure(error as NSError)
            }
        }
    }

    public func responseXMLDocument(completionHandler: Response<ONOXMLDocument, NSError> -> Void) -> Self {
        return response(responseSerializer: Request.XMLResponseSerializer(), completionHandler: completionHandler)
    }
}

Generic Response Object Serialization

Generics can be used to provide automatic, type-safe response object serialization.

public protocol ResponseObjectSerializable {
    init?(response: NSHTTPURLResponse, representation: AnyObject)
}

extension Request {
    public func responseObject<T: ResponseObjectSerializable>(completionHandler: Response<T, NSError> -> Void) -> Self {
        let responseSerializer = ResponseSerializer<T, NSError> { request, response, data, error in
            guard error == nil else { return .Failure(error!) }

            let JSONResponseSerializer = Request.JSONResponseSerializer(options: .AllowFragments)
            let result = JSONResponseSerializer.serializeResponse(request, response, data, error)

            switch result {
            case .Success(let value):
                if let
                    response = response,
                    responseObject = T(response: response, representation: value)
                {
                    return .Success(responseObject)
                } else {
                    let failureReason = "JSON could not be serialized into response object: \(value)"
                    let error = Error.errorWithCode(.JSONSerializationFailed, failureReason: failureReason)
                    return .Failure(error)
                }
            case .Failure(let error):
                return .Failure(error)
            }
        }

        return response(responseSerializer: responseSerializer, completionHandler: completionHandler)
    }
}
final class User: ResponseObjectSerializable {
    let username: String
    let name: String

    init?(response: NSHTTPURLResponse, representation: AnyObject) {
        self.username = response.URL!.lastPathComponent!
        self.name = representation.valueForKeyPath("name") as! String
    }
}
Alamofire.request(.GET, "https://example.com/users/mattt")
         .responseObject { (response: Response<User, NSError>) in
             debugPrint(response)
         }

The same approach can also be used to handle endpoints that return a representation of a collection of objects:

public protocol ResponseCollectionSerializable {
    static func collection(response response: NSHTTPURLResponse, representation: AnyObject) -> [Self]
}

extension Alamofire.Request {
    public func responseCollection<T: ResponseCollectionSerializable>(completionHandler: Response<[T], NSError> -> Void) -> Self {
        let responseSerializer = ResponseSerializer<[T], NSError> { request, response, data, error in
            guard error == nil else { return .Failure(error!) }

            let JSONSerializer = Request.JSONResponseSerializer(options: .AllowFragments)
            let result = JSONSerializer.serializeResponse(request, response, data, error)

            switch result {
            case .Success(let value):
                if let response = response {
                    return .Success(T.collection(response: response, representation: value))
                } else {
                    let failureReason = "Response collection could not be serialized due to nil response"
                    let error = Error.errorWithCode(.JSONSerializationFailed, failureReason: failureReason)
                    return .Failure(error)
                }
            case .Failure(let error):
                return .Failure(error)
            }
        }

        return response(responseSerializer: responseSerializer, completionHandler: completionHandler)
    }
}
final class User: ResponseObjectSerializable, ResponseCollectionSerializable {
    let username: String
    let name: String

    init?(response: NSHTTPURLResponse, representation: AnyObject) {
        self.username = response.URL!.lastPathComponent!
        self.name = representation.valueForKeyPath("name") as! String
    }

    static func collection(response response: NSHTTPURLResponse, representation: AnyObject) -> [User] {
        var users: [User] = []

        if let representation = representation as? [[String: AnyObject]] {
            for userRepresentation in representation {
                if let user = User(response: response, representation: userRepresentation) {
                    users.append(user)
                }
            }
        }

        return users
    }
}
Alamofire.request(.GET, "http://example.com/users")
         .responseCollection { (response: Response<[User], NSError>) in
             debugPrint(response)
         }

URLStringConvertible

Types adopting the URLStringConvertible protocol can be used to construct URL strings, which are then used to construct URL requests. NSString, NSURL, NSURLComponents, and NSURLRequest conform to URLStringConvertible by default, allowing any of them to be passed as URLString parameters to the request, upload, and download methods:

let string = NSString(string: "https://httpbin.org/post")
Alamofire.request(.POST, string)

let URL = NSURL(string: string)!
Alamofire.request(.POST, URL)

let URLRequest = NSURLRequest(URL: URL)
Alamofire.request(.POST, URLRequest) // overrides `HTTPMethod` of `URLRequest`

let URLComponents = NSURLComponents(URL: URL, resolvingAgainstBaseURL: true)
Alamofire.request(.POST, URLComponents)

Applications interacting with web applications in a significant manner are encouraged to have custom types conform to URLStringConvertible as a convenient way to map domain-specific models to server resources.

Type-Safe Routing

extension User: URLStringConvertible {
    static let baseURLString = "http://example.com"

    var URLString: String {
        return User.baseURLString + "/users/\(username)/"
    }
}
let user = User(username: "mattt")
Alamofire.request(.GET, user) // http://example.com/users/mattt

URLRequestConvertible

Types adopting the URLRequestConvertible protocol can be used to construct URL requests. NSURLRequest conforms to URLRequestConvertible by default, allowing it to be passed into request, upload, and download methods directly (this is the recommended way to specify custom HTTP body for individual requests):

let URL = NSURL(string: "https://httpbin.org/post")!
let mutableURLRequest = NSMutableURLRequest(URL: URL)
mutableURLRequest.HTTPMethod = "POST"

let parameters = ["foo": "bar"]

do {
    mutableURLRequest.HTTPBody = try NSJSONSerialization.dataWithJSONObject(parameters, options: NSJSONWritingOptions())
} catch {
    // No-op
}

mutableURLRequest.setValue("application/json", forHTTPHeaderField: "Content-Type")

Alamofire.request(mutableURLRequest)

Applications interacting with web applications in a significant manner are encouraged to have custom types conform to URLRequestConvertible as a way to ensure consistency of requested endpoints. Such an approach can be used to abstract away server-side inconsistencies and provide type-safe routing, as well as manage authentication credentials and other state.

API Parameter Abstraction

enum Router: URLRequestConvertible {
    static let baseURLString = "http://example.com"
    static let perPage = 50

    case Search(query: String, page: Int)

    // MARK: URLRequestConvertible

    var URLRequest: NSMutableURLRequest {
        let result: (path: String, parameters: [String: AnyObject]) = {
            switch self {
            case .Search(let query, let page) where page > 1:
                return ("/search", ["q": query, "offset": Router.perPage * page])
            case .Search(let query, _):
                return ("/search", ["q": query])
            }
        }()

        let URL = NSURL(string: Router.baseURLString)!
        let URLRequest = NSURLRequest(URL: URL.URLByAppendingPathComponent(result.path))
        let encoding = Alamofire.ParameterEncoding.URL

        return encoding.encode(URLRequest, parameters: result.parameters).0
    }
}
Alamofire.request(Router.Search(query: "foo bar", page: 1)) // ?q=foo%20bar&offset=50

CRUD & Authorization

enum Router: URLRequestConvertible {
    static let baseURLString = "http://example.com"
    static var OAuthToken: String?

    case CreateUser([String: AnyObject])
    case ReadUser(String)
    case UpdateUser(String, [String: AnyObject])
    case DestroyUser(String)

    var method: Alamofire.Method {
        switch self {
        case .CreateUser:
            return .POST
        case .ReadUser:
            return .GET
        case .UpdateUser:
            return .PUT
        case .DestroyUser:
            return .DELETE
        }
    }

    var path: String {
        switch self {
        case .CreateUser:
            return "/users"
        case .ReadUser(let username):
            return "/users/\(username)"
        case .UpdateUser(let username, _):
            return "/users/\(username)"
        case .DestroyUser(let username):
            return "/users/\(username)"
        }
    }

    // MARK: URLRequestConvertible

    var URLRequest: NSMutableURLRequest {
        let URL = NSURL(string: Router.baseURLString)!
        let mutableURLRequest = NSMutableURLRequest(URL: URL.URLByAppendingPathComponent(path))
        mutableURLRequest.HTTPMethod = method.rawValue

        if let token = Router.OAuthToken {
            mutableURLRequest.setValue("Bearer \(token)", forHTTPHeaderField: "Authorization")
        }

        switch self {
        case .CreateUser(let parameters):
            return Alamofire.ParameterEncoding.JSON.encode(mutableURLRequest, parameters: parameters).0
        case .UpdateUser(_, let parameters):
            return Alamofire.ParameterEncoding.URL.encode(mutableURLRequest, parameters: parameters).0
        default:
            return mutableURLRequest
        }
    }
}
Alamofire.request(Router.ReadUser("mattt")) // GET /users/mattt

SessionDelegate

By default, an Alamofire Manager instance creates an internal SessionDelegate object to handle all the various types of delegate callbacks that are generated by the underlying NSURLSession. The implementations of each delegate method handle the most common use cases for these types of calls abstracting the complexity away from the top-level APIs. However, advanced users may find the need to override the default functionality for various reasons.

Override Closures

The first way to customize the SessionDelegate behavior is through the use of the override closures. Each closure gives you the ability to override the implementation of the matching SessionDelegate API, yet still use the default implementation for all other APIs. This makes it easy to customize subsets of the delegate functionality. Here are a few examples of some of the override closures available:

/// Overrides default behavior for NSURLSessionDelegate method `URLSession:didReceiveChallenge:completionHandler:`.
public var sessionDidReceiveChallenge: ((NSURLSession, NSURLAuthenticationChallenge) -> (NSURLSessionAuthChallengeDisposition, NSURLCredential?))?

/// Overrides default behavior for NSURLSessionDelegate method `URLSessionDidFinishEventsForBackgroundURLSession:`.
public var sessionDidFinishEventsForBackgroundURLSession: ((NSURLSession) -> Void)?

/// Overrides default behavior for NSURLSessionTaskDelegate method `URLSession:task:willPerformHTTPRedirection:newRequest:completionHandler:`.
public var taskWillPerformHTTPRedirection: ((NSURLSession, NSURLSessionTask, NSHTTPURLResponse, NSURLRequest) -> NSURLRequest?)?

/// Overrides default behavior for NSURLSessionDataDelegate method `URLSession:dataTask:willCacheResponse:completionHandler:`.
public var dataTaskWillCacheResponse: ((NSURLSession, NSURLSessionDataTask, NSCachedURLResponse) -> NSCachedURLResponse?)?

The following is a short example of how to use the taskWillPerformHTTPRedirection to avoid following redirects to any apple.com domains.

let delegate: Alamofire.Manager.SessionDelegate = manager.delegate

delegate.taskWillPerformHTTPRedirection = { session, task, response, request in
    var finalRequest = request

    if let originalRequest = task.originalRequest where originalRequest.URLString.containsString("apple.com") {
        finalRequest = originalRequest
    }

    return finalRequest
}

Subclassing

Another way to override the default implementation of the SessionDelegate is to subclass it. Subclassing allows you completely customize the behavior of the API or to create a proxy for the API and still use the default implementation. Creating a proxy allows you to log events, emit notifications, provide pre and post hook implementations, etc. Here’s a quick example of subclassing the SessionDelegate and logging a message when a redirect occurs.

class LoggingSessionDelegate: Manager.SessionDelegate {
    override func URLSession(
        session: NSURLSession,
        task: NSURLSessionTask,
        willPerformHTTPRedirection response: NSHTTPURLResponse,
        newRequest request: NSURLRequest,
        completionHandler: NSURLRequest? -> Void)
    {
        print("URLSession will perform HTTP redirection to request: \(request)")

        super.URLSession(
            session,
            task: task,
            willPerformHTTPRedirection: response,
            newRequest: request,
            completionHandler: completionHandler
        )
    }
}

Generally, either the default implementation or the override closures should provide the necessary functionality required. Subclassing should only be used as a last resort.

It is important to keep in mind that the subdelegates are initialized and destroyed in the default implementation. Be careful when subclassing to not introduce memory leaks.

Security

Using a secure HTTPS connection when communicating with servers and web services is an important step in securing sensitive data. By default, Alamofire will evaluate the certificate chain provided by the server using Apple’s built in validation provided by the Security framework. While this guarantees the certificate chain is valid, it does not prevent man-in-the-middle (MITM) attacks or other potential vulnerabilities. In order to mitigate MITM attacks, applications dealing with sensitive customer data or financial information should use certificate or public key pinning provided by the ServerTrustPolicy.

ServerTrustPolicy

The ServerTrustPolicy enumeration evaluates the server trust generally provided by an NSURLAuthenticationChallenge when connecting to a server over a secure HTTPS connection.

let serverTrustPolicy = ServerTrustPolicy.PinCertificates(
    certificates: ServerTrustPolicy.certificatesInBundle(),
    validateCertificateChain: true,
    validateHost: true
)

There are many different cases of server trust evaluation giving you complete control over the validation process:

  • PerformDefaultEvaluation: Uses the default server trust evaluation while allowing you to control whether to validate the host provided by the challenge.
  • PinCertificates: Uses the pinned certificates to validate the server trust. The server trust is considered valid if one of the pinned certificates match one of the server certificates.
  • PinPublicKeys: Uses the pinned public keys to validate the server trust. The server trust is considered valid if one of the pinned public keys match one of the server certificate public keys.
  • DisableEvaluation: Disables all evaluation which in turn will always consider any server trust as valid.
  • CustomEvaluation: Uses the associated closure to evaluate the validity of the server trust thus giving you complete control over the validation process. Use with caution.

Server Trust Policy Manager

The ServerTrustPolicyManager is responsible for storing an internal mapping of server trust policies to a particular host. This allows Alamofire to evaluate each host against a different server trust policy.

let serverTrustPolicies: [String: ServerTrustPolicy] = [
    "test.example.com": .PinCertificates(
        certificates: ServerTrustPolicy.certificatesInBundle(),
        validateCertificateChain: true,
        validateHost: true
    ),
    "insecure.expired-apis.com": .DisableEvaluation
]

let manager = Manager(
    serverTrustPolicyManager: ServerTrustPolicyManager(policies: serverTrustPolicies)
)

Make sure to keep a reference to the new Manager instance, otherwise your requests will all get cancelled when your manager is deallocated.

These server trust policies will result in the following behavior:

  • test.example.com will always use certificate pinning with certificate chain and host validation enabled thus requiring the following criteria to be met to allow the TLS handshake to succeed:
    • Certificate chain MUST be valid.
    • Certificate chain MUST include one of the pinned certificates.
    • Challenge host MUST match the host in the certificate chain’s leaf certificate.

  • insecure.expired-apis.com will never evaluate the certificate chain and will always allow the TLS handshake to succeed.
  • All other hosts will use the default evaluation provided by Apple.
Subclassing Server Trust Policy Manager

If you find yourself needing more flexible server trust policy matching behavior (i.e. wildcarded domains), then subclass the ServerTrustPolicyManager and override the serverTrustPolicyForHost method with your own custom implementation.

class CustomServerTrustPolicyManager: ServerTrustPolicyManager {
    override func serverTrustPolicyForHost(host: String) -> ServerTrustPolicy? {
        var policy: ServerTrustPolicy?

        // Implement your custom domain matching behavior...

        return policy
    }
}

Validating the Host

The .PerformDefaultEvaluation, .PinCertificates and .PinPublicKeys server trust policies all take a validateHost parameter. Setting the value to true will cause the server trust evaluation to verify that hostname in the certificate matches the hostname of the challenge. If they do not match, evaluation will fail. A validateHost value of false will still evaluate the full certificate chain, but will not validate the hostname of the leaf certificate.

It is recommended that validateHost always be set to true in production environments.

Validating the Certificate Chain

Pinning certificates and public keys both have the option of validating the certificate chain using the validateCertificateChain parameter. By setting this value to true, the full certificate chain will be evaluated in addition to performing a byte equality check against the pinned certificates or public keys. A value of false will skip the certificate chain validation, but will still perform the byte equality check.

There are several cases where it may make sense to disable certificate chain validation. The most common use cases for disabling validation are self-signed and expired certificates. The evaluation would always fail in both of these cases, but the byte equality check will still ensure you are receiving the certificate you expect from the server.

It is recommended that validateCertificateChain always be set to true in production environments.

App Transport Security

With the addition of App Transport Security (ATS) in iOS 9, it is possible that using a custom ServerTrustPolicyManager with several ServerTrustPolicy objects will have no effect. If you continuously see CFNetwork SSLHandshake failed (-9806) errors, you have probably run into this problem. Apple’s ATS system overrides the entire challenge system unless you configure the ATS settings in your app’s plist to disable enough of it to allow your app to evaluate the server trust.

If you run into this problem (high probability with self-signed certificates), you can work around this issue by adding the following to your Info.plist.

<dict>
    <key>NSAppTransportSecurity</key>
    <dict>
        <key>NSExceptionDomains</key>
        <dict>
            <key>example.com</key>
            <dict>
                <key>NSExceptionAllowsInsecureHTTPLoads</key>
                <true/>
                <key>NSExceptionRequiresForwardSecrecy</key>
                <false/>
                <key>NSIncludesSubdomains</key>
                <true/>
                <!-- Optional: Specify minimum TLS version -->
                <key>NSTemporaryExceptionMinimumTLSVersion</key>
                <string>TLSv1.2</string>
            </dict>
        </dict>
    </dict>
</dict>

Whether you need to set the NSExceptionRequiresForwardSecrecy to NO depends on whether your TLS connection is using an allowed cipher suite. In certain cases, it will need to be set to NO. The NSExceptionAllowsInsecureHTTPLoads MUST be set to YES in order to allow the SessionDelegate to receive challenge callbacks. Once the challenge callbacks are being called, the ServerTrustPolicyManager will take over the server trust evaluation. You may also need to specify the NSTemporaryExceptionMinimumTLSVersion if you’re trying to connect to a host that only supports TLS versions less than 1.2.

It is recommended to always use valid certificates in production environments.

Network Reachability

The NetworkReachabilityManager listens for reachability changes of hosts and addresses for both WWAN and WiFi network interfaces.

let manager = NetworkReachabilityManager(host: "www.apple.com")

manager?.listener = { status in
    print("Network Status Changed: \(status)")
}

manager?.startListening()

Make sure to remember to retain the manager in the above example, or no status changes will be reported.

There are some important things to remember when using network reachability to determine what to do next.

  • Do NOT use Reachability to determine if a network request should be sent.
    • You should ALWAYS send it.

  • When Reachability is restored, use the event to retry failed network requests.
    • Even though the network requests may still fail, this is a good moment to retry them.

  • The network reachability status can be useful for determining why a network request may have failed.
    • If a network request fails, it is more useful to tell the user that the network request failed due to being offline rather than a more technical error, such as “request timed out.”

It is recommended to check out WWDC 2012 Session 706, “Networking Best Practices” for more info.


Open Rdars

The following rdars have some affect on the current implementation of Alamofire.

  • rdar://21349340 - Compiler throwing warning due to toll-free bridging issue in test case

FAQ

What’s the origin of the name Alamofire?

Alamofire is named after the Alamo Fire flower, a hybrid variant of the Bluebonnet, the official state flower of Texas.


Credits

Alamofire is owned and maintained by the Alamofire Software Foundation. You can follow them on Twitter at @AlamofireSF for project updates and releases.

Security Disclosure

If you believe you have identified a security vulnerability with Alamofire, you should report it as soon as possible via email to security@alamofire.org. Please do not post it to a public issue tracker.

License

Alamofire is released under the MIT license. See LICENSE for details.