Set the maximum character length of a UITextField

Question

How can I set the maximum amount of characters in a UITextField on the iPhone SDK when I load up a UIView?

Answer 1

Often you have multiple input fields with a different length.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    int allowedLength;
    switch(textField.tag) {
        case 1: 
            allowedLength = MAXLENGTHNAME;      // triggered for input fields with tag = 1
            break;
        case 2:
            allowedLength = MAXLENGTHADDRESS;   // triggered for input fields with tag = 2
            break;
        default:
            allowedLength = MAXLENGTHDEFAULT;   // length default when no tag (=0) value =255
            break;
    }

    if (textField.text.length >= allowedLength && range.length == 0) {
        return NO; // Change not allowed
    } else {
        return YES; // Change allowed
    }
}

Answer 2

swift 3.0

This code is working fine when you are paste string more than your character limits.

func textView(_ textView: UITextView, shouldChangeTextIn range: NSRange, replacementText text: String) -> Bool {
        let str = (textView.text + text)
        if str.characters.count <= 10 {
            return true
        }
        textView.text = str.substring(to: str.index(str.startIndex, offsetBy: 10))
        return false
    }

Thanks for your votes. :)

Answer 3

I did this in Swift for an 8 character limit when using a number pad.

func textField(textField: UITextField, shouldChangeCharactersInRange range: NSRange, replacementString string: String) -> Bool {
    return !(textField.text?.characters.count == MAX_LENGTH && string != "")
}

I had to test for string != "" to allow the delete button to work on the number pad, otherwise it wouldn't allow deleting characters in the text field after it reached its max.

Answer 4

Thank you august! (Post)

This is the code that I ended up with which works:

#define MAX_LENGTH 20

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    if (textField.text.length >= MAX_LENGTH && range.length == 0)
    {
        return NO; // return NO to not change text
    }
    else
    {return YES;}
}

Answer 5

This should be enough to solve the problem (replace 4 by the limit u want). Just make sure to add delegate in IB.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
     NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string];
     return (newString.length<=4);
}

Answer 6

Got it down to 1 line of code :)

Set your text view's delegate to "self" then add the <UITextViewDelegate> in your .h and the following code in your .m .... you can adjust the number "7" to be whatever you want your MAXIMUM number of characters to be.

-(BOOL)textView:(UITextView *)a shouldChangeTextInRange:(NSRange)b replacementText:(NSString *)c {
    return ((a.text.length+c.length<=7)+(c.length<1)+(b.length>=c.length)>0);
}

This code accounts for typing new characters, deleting characters, selecting characters then typing or deleting, selecting characters and cutting, pasting in general, and selecting characters and pasting.

Done!

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Alternatively, another cool way to write this code with bit-operations would be

-(BOOL)textView:(UITextView *)a shouldChangeTextInRange:(NSRange)b replacementText:(NSString *)c {
    return 0^((a.text.length+c.length<=7)+(c.length<1)+(b.length>=c.length));
}