How to enable a UIButton if a textfield is not empty?

I'm having a problem with my UITextField and three UIButtons. I want to disable the buttons when the UITextfield is empty and re-enable when it has text on it. I already tried this:

- (IBAction)validateFields:(id)sender {



    NSString *trimName = [URLToTrim stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
    if (trimName.length >0)

    {
        trim.enabled = 1;
        trim2.enabled = 1;
        trim3.enabled =1;
        // proceed with your inserting values

    }


}

And this:

-(void)viewDidLoad {
if([URLToTrim.text isEqualToString: @""]){  
    trim.hidden = YES;  
    trim2.hidden = YES;
    trim3.hidden = YES;

} else {  
    trim.hidden = NO;  
    trim2.hidden = NO;
    trim3.hidden = NO;   
}

and lastly, this:

-(void)viewDidLoad {
    if ([URLToTrim.text isEqualToString:@""]) {
        trim.enabled = 0;
        trim2.enabled= 0;
        trim3.enabled = 0;
    } 

But with the first one the app cr开发者_开发百科ashes when writing and with the second one the buttons aren't being re-enabled. Thanks in advance for the help :)

It seems URLToTrim is a UITextField? The problem in the first is that you're calling stringByTrimmingCharactersInSet: on the text field itself, instead of the value of the text field. You do it right in the other two, using URLToTrim.text.

The problem with the second is that viewDidLoad is only called when the view is first loaded, so it never gets called again to re-enable the buttons. You want to do that code in one of the methods of your UITextFieldDelegate (which may already be your same view controller), probably textField:shouldChangeCharactersInRange:replacementString: although textFieldShouldEndEditing:/textFieldDidEndEditing: could work if you only want the buttons to be updated when you finish editing.