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Input Mask

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Input Mask


The library allows to format user input on the fly according to the provided mask and to extract valueable characters.

Masks consist of blocks of symbols, which may include:

  • [] — a block for valueable symbols written by user.

Square brackets block may contain any number of special symbols:

  1. 0 — mandatory digit. For instance, [000] mask will allow user to enter three numbers: 123.
  2. 9 — optional digit . For instance, [00099] mask will allow user to enter from three to five numbers.
  3. А — mandatory letter. [AAA] mask will allow user to enter three letters: abc.
  4. а — optional letter. [АААааа] mask will allow to enter from three to six letters.
  5. _ — mandatory symbol (digit or letter).
  6. - — optional symbol (digit or letter).

Other symbols inside square brackets will cause a mask initialization error.

Blocks may contain mixed types of symbols; such that, [000AA] will end up being divided in two groups: [000][AA] (this happens automatically).

Blocks must not contain nested brackets. [[00]000] format will cause a mask initialization error.

Symbols outside the square brackets will take a place in the output. For instance, +7 ([000]) [000]-[0000] mask will format the input field to the form of +7 (123) 456-7890.

  • {} — a block for valueable yet fixed symbols, which could not be altered by the user.

Symbols within the square and curly brackets form an extracted value (valueable characters). In other words, [00]-[00] and [00]{-}[00] will format the input to the same form of 12-34, but in the first case the value, extracted by the library, will be equal to 1234, and in the second case it will result in 12-34.

Mask format examples:

  1. [00000000000]
  2. {401}-[000]-[00]-[00]
  3. [000999999]
  4. {818}-[000]-[00]-[00]
  5. [A][-----------------------------------------------------]
  6. [A][_______________________________________________________________]
  7. 8 [0000000000]
  8. 8([000])[000]-[00]-[00]
  9. [0000]{-}[00]
  10. +1 ([000]) [000] [00] [00]



pod 'InputMask'


git "https://github.com/RedMadRobot/input-mask-ios.git"

Swift Package Manager

dependencies: [
    .Package(url: "https://github.com/RedMadRobot/input-mask-ios", majorVersion: 3)


Simple UITextField for the phone numbers

Listening to the text change events of UITextField and simultaneously altering the entered text could be a bit tricky as long as you need to add, remove and replace symbols intelligently preserving the cursor position.

Thus, the library provides corresponding MaskedTextFieldDelegate class.

MaskedTextFieldDelegate conforms to UITextFieldDelegate protocol and encaspulates logic to process text edit events. The object might be instantiated via code or might be dropped on the Interface Builder canvas as an NSObject and then wired with the corresponding UITextField.

MaskedTextFieldDelegate has his own listener MaskedTextFieldDelegateListener, which extends UITextFieldDelegate protocol with a callback providing actual extracted value. All the UITextFieldDelegate calls from the client UITextField are forwarded to the MaskedTextFieldDelegateListener object, yet it doesn't allow to override textField(textField:shouldChangeCharactersIn:replacementString:) result, always returning false.

Interface Builder

class ViewController: UIViewController, MaskedTextFieldDelegateListener {
    var maskedDelegate: MaskedTextFieldDelegate!

    @IBOutlet weak var field: UITextField!
    open override func viewDidLoad() {
        maskedDelegate = MaskedTextFieldDelegate(format: "{+7} ([000]) [000] [00] [00]")
        maskedDelegate.listener = self

        field.delegate = maskedDelegate

        maskedDelegate.put(text: "+7 123", into: field)
    open func textField(
        _ textField: UITextField, 
        didFillMandatoryCharacters complete: Bool,
        didExtractValue value: String
    ) {

Sample project might be found under Source/Sample

String formatting without views

In case you want to format a String somewhere in your applicaiton's code, Mask is the class you are looking for. Instantiate a Mask instance and feed it with your string, mocking the cursor position:

let mask: Mask = try! Mask(format: "+7 ([000]) [000] [00] [00]")
let input: String = "+71234567890"
let result: Mask.Result = mask.apply(
    toText: CaretString(
        string: input,
        caretPosition: input.endIndex
    autocomplete: true // you may consider disabling autocompletion for your case
let output: String = result.formattedText.string

Affine masks

An experimental feature. While transforming the text, Mask calculates affinity index, which is basically an Int that shows the absolute rate of similarity between the text and the mask pattern.

This index might be used to choose the most suitable pattern between predefined, and then applied to format the text.

For the implementation, look for the PolyMaskTextFieldDelegate class, which inherits logic from MaskedTextFieldDelegate. It has its primary mask pattern and corresponding list of affine formats.

open class ViewController: UIViewController, MaskedTextFieldDelegateListener {
    @IBOutlet weak var listener: PolyMaskTextFieldDelegate!
    @IBOutlet weak var field: UITextField!
    open override func viewDidLoad() {
        listener.affineFormats = [
            "8 ([000]) [000] [00] [00]"
    open func textField(
        _ textField: UITextField, 
        didFillMandatoryCharacters complete: Bool,
        didExtractValue value: String
    ) {

Known issues

UITextFieldTextDidChange notification and target-action editingChanged event

UITextField with assigned MaskedTextFieldDelegate or PolyMaskTextFieldDelegate object won't issue UITextFieldTextDidChange notifications and editingChanged control events. This happens due to the textField(_:shouldChangeCharactersIn:replacementString:) method implementation, which always returns false.

Consider using following workaround in case if you do really need to catch editing events:

class NotifyingMaskedTextFieldDelegate: MaskedTextFieldDelegate {
    weak var editingListener: NotifyingMaskedTextFieldDelegateListener?
    override func textField(
        _ textField: UITextField,
        shouldChangeCharactersIn range: NSRange,
        replacementString string: String
    ) -> Bool {
        defer {
            self.editingListener?.onEditingChanged(inTextField: textField)
        return super.textField(textField, shouldChangeCharactersIn: range, replacementString: string)

protocol NotifyingMaskedTextFieldDelegateListener: class {
    func onEditingChanged(inTextField: UITextField)

Please, avoid at all costs sending SDK events and notifications manually.

Carthage vs. IBDesignables, IBInspectables, views and their outlets

Interface Builder struggles to support modules imported in a form of a dynamic framework. For instance, custom views annotated as IBDesignable, containing IBInspectable and IBOutlet fields aren't recognized properly from the drag'n'dropped *.framework.

In case you are using our library as a Carthage-built dynamic framework, be aware you won't be able to easily wire your MaskedTextFieldDelegate objects and their listeners from storyboards in your project. There is a couple of workarounds described in the corresponding discussion, though.

Also, consider filing a radar to Apple, like this one.


The library is distributed under the MIT LICENSE.


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