How to check text field input at real time?

Question

I am writing validation for my textfield, I found something interesting that whether I can check how many digits I am typing into the textfield at real time. My text field i

Answer 1

Update Swift 4.0

 txtFieldAdd.addTarget(self, action: #selector(textFieldDidChange(_:)), for: .editingChanged)

Now call your function. In my case, this will enable the save button

@objc func textFieldDidChange(_ textField: UITextField) {
    if (txtFieldAdd.text?.isEmpty)! {
        btnSave.isEnabled = false
    }
    else {
        btnSave.isEnabled = true
    }
}

Hope it helps.

Answer 2

This is how you get realtime validation without setting up anything other than the delegate of the textfield:

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {

    // Creating the future string. The incoming string can be a single character,
    // empty (on delete) or many characters when the user is pasting text.

    let futureString: String = ((textField.text ?? "") as NSString).replacingCharacters(in: range, with: string)

    // Determine if the change is allowed, update form, etc.
    let allowChange = <#Your Validation Code#>

    return allowChange
}

Add this code to the designated delegate of the textfield. Simple.

Answer 3

[textField addTarget:self action:@selector(checkTextField) forControlEvents:UIControlEventEditingChanged];

Try it!

Answer 4

Use UITextFieldDelegate. especially this function

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string

and you can get sample codes links from here..

Answer 5

Set up a delegate for the UITextField and implement the method – textField:shouldChangeCharactersInRange:replacementString: Details and examples are in the UITextFieldDelegate Protocol Reference, but here's a quick example:

- (BOOL)textField:(UITextField *)textField 
shouldChangeCharactersInRange:(NSRange)range 
replacementString:(NSString *)string
{
        NSString *text = [textField text];
        // NOT BACKSPACE
        if ([string length] || text.length + string.length < 8) {
            return YES;
        } else if (text.length + string.length > 8) {
            return NO;
        } else {
                // DO SOMETHING FOR LENGTH == 8
                return YES;
        }
}   

Answer 6

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSString * searchStr = [textField.text stringByReplacingCharactersInRange:range withString:string];

//    [textField2 setText:[textField1.text stringByReplacingCharactersInRange:range withString:string]];
    NSLog(@"%@",searchStr);
    return YES;
}