UITextField replace text with NSUndoManager Support

Question

I'm just using a simple

self.customerTextField.text = @"text";

but I would like there to be undo support, where if they shake the phone they can undo the change.

I'm kinda at a loss as to how to accomplish this. All the exapmles I find are for UITextView.

======================== Current iteration of code ======================

-(void)getUniqueItemID {

    [self.inventoryLibrarian generateUniqueItemIDwithCompletionBlock:^(NSString *string) {

        [self undoTextFieldEdit:string];
        //self.customTextField.text = string;

    }];

}

- (void)undoTextFieldEdit: (NSString*)string
{
    [self.undoManager registerUndoWithTarget:self
                                    selector:@selector(undoTextFieldEdit:)
                                      object:self.customTextField.text];
    self.customTextField.text = string;
}

-(BOOL)canBecomeFirstResponder {
    return YES;
}

Answer 1

Shake-to-undo
Put this line in your appDelegate's application:didFinishLaunchingWithOptions: method:

    application.applicationSupportsShakeToEdit = YES;

and in the relevant viewController.m

    -(BOOL)canBecomeFirstResponder {
        return YES;
    }

the rest of this code goes in viewController.m

Property
Put this in the class extension...

    @interface myViewController()
    @property (weak, nonatomic) IBOutlet UITextField *inputTextField;
    @end

link it up to your text field in Interface Builder.

Undo method
Adds an invocation of itself to the redo stack

    - (void)undoTextFieldEdit: (NSString*)string
    {
        [self.undoManager registerUndoWithTarget:self
                                        selector:@selector(undoTextFieldEdit:)
                                          object:self.inputTextField.text];
        self.inputTextField.text = string;
    }

(we do not need to create an NSUndoManager instance, we inherit one from the UIResponder superclass)

Undo actions
Not required for shake-to-undo, but could be useful...

    - (IBAction)undo:(id)sender {
        [self.undoManager undo];
    }
    - (IBAction)redo:(id)sender {
        [self.undoManager redo];
    }

Invocations of the undo method
Here are two different examples of changing the textField's contents…

Example 1
Set the textField's contents from a button action

    - (IBAction)addLabelText:(UIButton*)sender {
        [self.undoManager registerUndoWithTarget:self
                                        selector:@selector(undoTextFieldEdit:)
                                          object:self.inputTextField.text];
        self.inputTextField.text = @"text";
    }

Risking loss of clarity, we can shorten this to:

    - (IBAction)addLabelText:(UIButton*)sender {
        [self undoTextFieldEdit: @"text"];
    }

as the undoManager invocation is the same in both methods

Example 2
Direct keyboard input editing

    #pragma mark - textField delegate methods

    - (BOOL)textFieldShouldBeginEditing:(UITextField *)textField
    {
        [self.undoManager registerUndoWithTarget:self
                                        selector:@selector(undoTextFieldEdit:)
                                          object:textField.text];
        return YES;
    }

    - (BOOL)textFieldShouldReturn:(UITextField *)textField
    {
        //to dismiss the keyboard
        [textField resignFirstResponder];
        return YES;
    }

Answer 2

You don't need to do anything, it just works unless you disable it. See this question for example.