Introduction
Welcome to the CompoundFetchedResultsController documentation. Here you will find detailed information about the CompoundFetchedResultsController framework. This framework provides a powerful way to manage and display data fetched from multiple Core Data entities.
Features
- Efficiently manages compound fetch requests
- Provides easy-to-use interface for handling fetch results
- Supports both real-time and batch updates
- Automatically updates UI based on fetched results changes
Installation
CocoaPods
To install CompoundFetchedResultsController using CocoaPods, add the following line to your Podfile:
pod 'CompoundFetchedResultsController'Then, run the pod install command in your terminal.
Manual Installation
If you prefer manual installation, follow these steps:
- Download the latest release of CompoundFetchedResultsController from the GitHub repository.
- Drag and drop the framework into your Xcode project.
- Ensure that the framework is added to your project’s target.
- That’s it! Now you are ready to use CompoundFetchedResultsController.
Usage
Initializing a CompoundFetchedResultsController
To use CompoundFetchedResultsController, you need to initialize it with the appropriate parameters.
// Initialize compound fetched results controller
let compoundFRC = CompoundFetchedResultsController(entityTypes: ["EntityOne", "EntityTwo"], predicates: [nil, predicate], sortDescriptors: [sortDescriptor, nil], delegate: self)The entityTypes parameter is an array of NSString values representing the names of the Core Data entities involved in the fetch.
The predicates parameter is an array of NSPredicate objects representing the search criteria for the fetch request. Use nil if no predicate is required for a specific entity.
The sortDescriptors parameter is an array of NSSortDescriptor objects specifying the order in which the fetched data should be displayed. Use nil if no sorting is required for a specific entity.
The delegate parameter should be set to the object that will act as the CompoundFetchedResultsControllerDelegate and handle the fetched results updates.
Implementing the Delegate Methods
To receive updates from the CompoundFetchedResultsController, you should implement the following delegate methods in the object set as the delegate:
func controllerWillChangeContent(_ controller: CompoundFetchedResultsController)
func controller(_ controller: CompoundFetchedResultsController, didChangeSection section: CompoundFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: CompoundFetchedResultsChangeType)
func controller(_ controller: CompoundFetchedResultsController, didChangeObject managedObject: NSManagedObject, atIndexPath indexPath: IndexPath?, forChangeType type: CompoundFetchedResultsChangeType)
func controller(_ controller: CompoundFetchedResultsController, didChangeObject updatedObject: NSManagedObject, atIndexPath indexPath: IndexPath?, forChangeType type: CompoundFetchedResultsChangeType, newIndexPath: IndexPath?)
func controllerDidChangeContent(_ controller: CompoundFetchedResultsController)
func controller(_ controller: CompoundFetchedResultsController, didFailWithError error: Error)These methods will notify you of changes in the fetched results, including section and object insertions, updates, deletions, and movements.
Example Code
Creating a CompoundFetchedResultsController
// Create a CompoundFetchedResultsController
let compoundFRC = CompoundFetchedResultsController(entityTypes: ["EntityOne", "EntityTwo"], predicates: [nil, predicate], sortDescriptors: [sortDescriptor, nil], delegate: self)
// Perform initial fetch
do {
try compoundFRC.performFetch()
} catch {
// Handle error
print("Error fetching data: \(error.localizedDescription)")
}Implementing Delegate Methods
Below is an example implementation of the CompoundFetchedResultsController delegate methods:
func controllerWillChangeContent(_ controller: CompoundFetchedResultsController) {
// Perform necessary UI preparation for fetched results changes
tableView.beginUpdates()
}
func controller(_ controller: CompoundFetchedResultsController, didChangeSection section: CompoundFetchedResultsSectionInfo, atIndex sectionIndex: Int, forChangeType type: CompoundFetchedResultsChangeType) {
// Handle section changes (insert, delete, move)
switch type {
case .insert:
tableView.insertSections(IndexSet(integer: sectionIndex), with: .fade)
case .delete:
tableView.deleteSections(IndexSet(integer: sectionIndex), with: .fade)
case .move:
tableView.moveSection(sectionIndex, toSection: sectionIndex)
default:
break
}
}
func controller(_ controller: CompoundFetchedResultsController, didChangeObject managedObject: NSManagedObject, atIndexPath indexPath: IndexPath?, forChangeType type: CompoundFetchedResultsChangeType) {
// Handle object changes (insert, delete, update)
switch type {
case .insert:
if let indexPath = indexPath {
tableView.insertRows(at: [indexPath], with: .fade)
}
case .delete:
if let indexPath = indexPath {
tableView.deleteRows(at: [indexPath], with: .fade)
}
case .update:
if let indexPath = indexPath {
tableView.reloadRows(at: [indexPath], with: .fade)
}
default:
break
}
}
func controllerDidChangeContent(_ controller: CompoundFetchedResultsController) {
// Perform necessary UI updates after fetched results changes
tableView.endUpdates()
}
func controller(_ controller: CompoundFetchedResultsController, didFailWithError error: Error) {
// Handle error
print("Failed to fetch data: \(error.localizedDescription)")
}Conclusion
Congratulations! You have successfully learned how to use CompoundFetchedResultsController. This framework provides an efficient and easy way to manage fetched data from multiple Core Data entities. Use it to enhance your app’s performance when dealing with compound fetch requests.