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iOS

Posted by Tom Coomer
Tom Coomer
1,331 Points

Text Field max length on Mac OSX

I have created an app for iOS that uses the code below to limit the length of a string in the text field to 1. I am now trying to create the app to run on Mac but cannot seem to work out how to do the same. Thanks (MAXLENGTH is = 1)

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

    NSUInteger oldLength = [textField.text length];
    NSUInteger replacementLength = [string length];
    NSUInteger rangeLength = range.length;

    NSUInteger newLength = oldLength - rangeLength + replacementLength;

    BOOL returnKey = [string rangeOfString: @"\n"].location != NSNotFound;

    return newLength <= MAXLENGTH || returnKey;
}

1 Answer

James Andrews
James Andrews
7,245 Points

The differences is that iOS uses different interface libraries than OS X. If you go to the your .xib file click on a text field and go to the Identity Inspector. You'll notice that it inherits from NSTextfield instead of UITextfield. NSTextfield is part of Appkit and if you look at the docs it doesn't have any methods or attributes. Therefore you need to capture the stringValue as an NSString and then get the length of the NSString.

so something like this would probably fix your problem, but I can't say for certain as I haven't tested this.

    NSString *textfieldString = [textField stringValue];
    NSUInteger oldLength = [textfieldString length];
    NSUInteger replacementLength = [string length];
    NSUInteger rangeLength = range.length;

    NSUInteger newLength = oldLength - rangeLength + replacementLength;

    BOOL returnKey = [string rangeOfString: @"\n"].location != NSNotFound;

    return newLength <= MAXLENGTH || returnKey;
Tom Coomer
Tom Coomer
1,331 Points

Excellent. Thank you. I will try it when I get back to my computer and let you know. Thanks again.

Tom Coomer
Tom Coomer
1,331 Points

How should I link this to the Text field? Should it be an IBAction?

James Andrews
James Andrews
7,245 Points

no same as iOS textfields go to an Outlet not an action. actions are for buttons etc..

Tom Coomer
Tom Coomer
1,331 Points

Okay. Thanks. I was wondering if you also know how I would clear a textfield when it becomes in focus (first responder)? Thanks

James Andrews
James Andrews
7,245 Points

Not sure, maybe set a delegate for it. I've very little Objective C experience making Mac apps. I had learned a long time ago and gave up because I didn't have the time to dedicate it. What I gave you I got from a google search ;-)

Tom Coomer
Tom Coomer
1,331 Points

Ah. Right. Ill keep looking. Thanks again.