A drop-in UIViewController subclass with a growing text input view and other useful messaging features. Meant to be a replacement for UITableViewController & UICollectionViewController.

Demo Gif

This library is used in Slack's iOS app. It was built to fit our needs, but is flexible enough to be reused by others wanting to build great messaging apps for iOS.

Feature List





With Cocoa Pods:
pod 'SlackTextViewController'

There are two ways to do this:

  • Copy and drag the Source/ folder to your project.
  • or compile the project located in Builder/SlackTextViewController.xcodeproj to create a SlackTextViewController.framework package. You could also link the library into your project.

How to use


SLKTextViewController is meant to be subclassed, like you would normally do with UITableViewController or UICollectionViewController or UIScrollView. This pattern is a convenient way of extending UIViewController. SlackTextViewController manages a lot behind the scenes while still providing the ability to add custom behaviours. You may override methods, and decide to call super and perform additional logic, or not to call super and override default logic.

Start by creating a new subclass of SLKTextViewController.

In the init overriding method, if you wish to use the UITableView version, call:

[super initWithTableViewStyle:UITableViewStylePlain]

or the UICollectionView version:

[super initWithCollectionViewLayout:[UICollectionViewFlowLayout new]]

or the UIScrollView version:

[super initWithScrollView:self.myStrongScrollView]

Protocols like UITableViewDelegate and UITableViewDataSource are already setup for you. You will be able to call whatever delegate and data source methods you need for customising your control.

Calling [super init] will call [super initWithTableViewStyle:UITableViewStylePlain] by default.


When using SlackTextViewController with storyboards, instead of overriding the traditional initWithCoder: you will need to override any of the two custom methods below. This approach helps preserving the exact same features from the programatic approach, but also limits the edition of the nib of your SLKTextViewController subclass since it doesn't layout subviews from the nib (subviews are still initialized and layed out programatically).

if you wish to use the UITableView version, call:

+ (UITableViewStyle)tableViewStyleForCoder:(NSCoder *)decoder
    return UITableViewStylePlain;

or the UICollectionView version:

+ (UICollectionViewLayout *)collectionViewLayoutForCoder:(NSCoder *)decoder
    return [UICollectionViewFlowLayout new];

Sample Project

Check out the sample project, everything is demo'd there. There are 2 main examples (different targets) for testing the programatic and storyboard approaches. Most of the features are implemented for you to quickly start using them.

A CollectionView example, using Swift, is in progress on the swift-example branch. The idea with this project is to build a custom collection view layout allowing to display cells from the bottom (currently working but needs serious tweaks to make it perfect). Feel free to contribute!


Growing Text View


The text view expands automatically when a new line is required, until it reaches its maxNumberOfLinesvalue. You may change this property's value in the textView.

By default, the number of lines is set to best fit each device dimensions:

  • iPhone 4 (<=480pts): 4 lines
  • iPhone 5/6 (>=568pts): 6 lines
  • iPad (>=768pts): 8 lines

On iPhone devices, in landscape orientation, the maximum number of lines is changed to fit the available space.

Inverted Mode

Some layouts may require to show from bottom to top and new subviews are inserted from the bottom. To enable this, you must use the inverted flag property (default is YES). This will actually invert the entire ScrollView object. Make sure to apply the same transformation to every subview. In the case of UITableView, the best place for adjusting the transformation is in its data source methods like:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
    UITableViewCell *cell = [self.tableView dequeueReusableCellWithIdentifier:chatCellIdentifier];
    cell.transform = self.tableView.transform;


We use autocompletion for many things: names, channels, emoji, and more.


To set up autocompletion in your app, follow these simple steps:

1. Registration

You must first register all the prefixes you'd like to support for autocompletion detection:

[self registerPrefixesForAutoCompletion:@[@"#"]];

2. Processing

Every time a new character is inserted in the text view, the nearest word to the caret will be processed and verified if it contains any of the registered prefixes.

Once the prefix has been detected, -didChangeAutoCompletionPrefix:andWord: will be called. This is the perfect place to populate your data source and show/hide the autocompletion view. So you must override it in your subclass, to be able to perform additional tasks. Default returns NO.

- (void)didChangeAutoCompletionPrefix:(NSString *)prefix andWord:(NSString *)word
    self.searchResult = [[NSArray alloc] initWithArray:self.channels];

    if ([prefix isEqualToString:@"#"])
        if (word.length > 0) {
            self.searchResult = [self.searchResult filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"self BEGINSWITH[c] %@ AND self !=[c] %@", word, word]];

    if (self.searchResult.count > 0) {
        self.searchResult = [self.searchResult sortedArrayUsingSelector:@selector(localizedCaseInsensitiveCompare:)];

    BOOL show = (self.searchResult.count > 0);

    [self showAutoCompletionView:show];

The autocompletion view is a UITableView instance, so you will need to use UITableViewDataSource to populate its cells. You have complete freedom for customizing the cells.

You don't need to call -reloadData yourself, since it will be invoked automatically right after calling the -showAutoCompletionView method.

3. Layout

The maximum height of the autocompletion view is set to 140 pts by default. You can update this value anytime, so the view automatically adjusts based on the amount of displayed cells.

- (CGFloat)heightForAutoCompletionView
    CGFloat cellHeight = 34.0;
    return cellHeight*self.searchResult.count;

4. Confirmation

If the user selects any autocompletion view cell on -tableView:didSelectRowAtIndexPath:, you must call -acceptAutoCompletionWithString: to commit autocompletion. That method expects a string matching the selected item, that you would like to be inserted in the text view.

- (void)tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath
    if ([tableView isEqual:self.autoCompletionView]) {

        NSString *item = self.searchResult[indexPath.row];

        [self acceptAutoCompletionWithString:item];

The autocompletion view will automatically be dismissed and the chosen string will be inserted in the text view, replacing the detected prefix and word.

You can always call -cancelAutoCompletion to exit the autocompletion mode and refresh the UI.

Edit Mode

Edit Mode

To enable edit mode, you simply need to call [self editText:@"hello"];, and the text input will switch to edit mode, removing both left and right buttons, extending the input bar a bit higher with "Accept" and "Cancel" buttons. Both of this buttons are accessible in the SLKTextInputbar instance for customisation.

To capture the "Accept" or "Cancel" events, you must override the following methods.

- (void)didCommitTextEditing:(id)sender
    NSString *message = [self.textView.text copy];

    [self.messages removeObjectAtIndex:0];
    [self.messages insertObject:message atIndex:0];
    [self.tableView reloadData];

    [super didCommitTextEditing:sender];

- (void)didCancelTextEditing:(id)sender
    [super didCancelTextEditing:sender];

Notice that you must call super at some point, so the text input exits the edit mode, re-adjusting the layout and clearing the text view. Use the editing property to know if the editing mode is on.

Markdown Formatting

Markdown Formatting

You can register markdown formatting symbols so they can easily be used to wrap a text selection, with the help of the native contextual menu, aka UIMenuController. This feature doesn't take care of the rendering of the markdown: it's sole purpose is to ease the formatting tools to the user. Optionally, you can enable autoCompleteFormatting so any pending markdown closure symbol can be added automatically after double tapping on the keyboard spacebar, just like the native gesture to add a sentence period. The sentence period is still being added as a fallback.

Markdown Formatting Animated

1. Registration

You must first register the formatting symbol and assign a title string to be used in the menu controller item.

[self.textView registerMarkdownFormattingSymbol:@"*" withTitle:@"Bold"];

2. Customisation

Futher more, you can customise some of the behavior for special formatting cases, using the UITextViewDelegate methods. In the following example, we don't present the Quote formatting in the contextual menu when the text selection isn't a paragraph.

- (BOOL)textView:(SLKTextView *)textView shouldOfferFormattingForSymbol:(NSString *)symbol
    if ([symbol isEqualToString:@">"]) {

        NSRange selection = textView.selectedRange;

        // The Quote formatting only applies new paragraphs
        if (selection.location == 0 && selection.length > 0) {
            return YES;

        // or older paragraphs too
        NSString *prevString = [textView.text substringWithRange:NSMakeRange(selection.location-1, 1)];

        if ([[NSCharacterSet newlineCharacterSet] characterIsMember:[prevString characterAtIndex:0]]) {
            return YES;

        return NO;

    return [super textView:textView shouldOfferFormattingForSymbol:symbol];

In this other method implementation, we don't want to allow auto-completion for the Quote formatting since it doesn't require a closure.

- (BOOL)textView:(SLKTextView *)textView shouldInsertSuffixForFormattingWithSymbol:(NSString *)symbol prefixRange:(NSRange)prefixRange
    if ([symbol isEqualToString:@">"]) {
        return NO;

    return [super textView:textView shouldInsertSuffixForFormattingWithSymbol:symbol prefixRange:prefixRange];

Typing Indicator

Typing Indicator

Optionally, you can enable a simple typing indicator, which will be displayed right above the text input. It shows the name of the people that are typing, and if more than 2, it will display "Several are typing" message.

To enable the typing indicator, just call [self.typingIndicatorView insertUsername:@"John"]; and the view will automatically be animated on top of the text input. After a default interval of 6 seconds, if the same name hasn't been assigned once more, the view will be dismissed with animation.

You can remove names from the list by calling [self.typingIndicatorView removeUsername:@"John"];

You can also dismiss it by calling [self.typingIndicatorView dismissIndicator];

Panning Gesture

Dismissing the keyboard with a panning gesture is enabled by default with the keyboardPanningEnabled property. You can always disable it if you'd like. You can extend the verticalPanGesture behaviors with the UIGestureRecognizerDelegate methods.

Hideable TextInputbar

Sometimes you may need to hide the text input bar. Very similar to UINavigationViewController's API, simply do:

[self setTextInputbarHidden:YES animated:YES];

Shake Gesture

Shake Gesture

A shake gesture to clear text is enabled by default with the undoShakingEnabled property.

You can optionally override -willRequestUndo, to implement your UI to ask the users if he would like to clean the text view's text. If there is not text entered, the method will not be called.

If you don't override -willRequestUndo and undoShakingEnabled is set to YES, a system UIAlertView will

External Keyboard

There a few basic key commands enabled by default:

  • cmd + z -> undo
  • shift + cmd + z -> redo
  • return key -> calls -didPressRightButton:, or -didCommitTextEditing: if in edit mode
  • shift/cmd + return key -> line break
  • escape key -> exits edit mode, or auto-completion mode, or dismisses the keyboard
  • up & down arrows -> vertical cursor movement

To add additional key commands, simply override -keyCommands and append super's array.

- (NSArray *)keyCommands
    NSMutableArray *commands = [NSMutableArray arrayWithArray:[super keyCommands]];

    // Edit last message
    [commands addObject:[UIKeyCommand keyCommandWithInput:UIKeyInputUpArrow

    return commands;

There are also a set of useful flags for keyboard special detections such as isExternalKeyboardDetected, isKeyboardUndocked, typingSuggestionEnabled and isTrackpadEnabled (iOS 9 only)

Dynamic Type

Dynamic Type is enabled by default with the dynamicTypeEnabled property. You can always disable it if you'd like, but the text input bar would still adjust to best fit the font size of the text view.


XCode Templates


We have prepared a set of useful XCode templates so you can quickly start using SlackTextViewController.

To install them, open up your terminal and type:

sh ./SlackTextViewController/File\ Templates/install.sh

These templates are also available in Alcatraz.