Set the maximum character length of a UITextField

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

Thank you august! ([Post][1])

[1]:

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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;}
}

To make it work with cut & paste of strings of any length, I would suggest changing the function to something like:

#define MAX_LENGTH 20

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
NSInteger insertDelta = string.length - range.length;

if (textField.text.length + insertDelta > MAX_LENGTH)
{
return NO; // the new string would be longer than MAX_LENGTH
}
else {
return YES;
}
}

Using Interface builder you can link and get the event for "Editing changed" in any of your function.
Now there you can put check for the length


- (IBAction)onValueChange:(id)sender
{
NSString *text = nil;
int MAX_LENGTH = 20;
switch ([sender tag] )
{
case 1:
{
text = myEditField.text;
if (MAX_LENGTH < [text length]) {
myEditField.text = [text substringToIndex:MAX_LENGTH];
}
}
break;
default:
break;
}

}

I found this quick and simple


- (IBAction)backgroundClick:(id)sender {
if (mytext.length <= 7) {
[mytext resignFirstResponder];
} else {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Too Big"
message:@"Please Shorten Name"
delegate:nil
cancelButtonTitle:@"Cancel"
otherButtonTitles:nil];
[alert show];
[alert release];
}
}

I simulate the actual string replacement that's about to happen to calculate that future string's length:

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

NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string];

if([newString length] > maxLength)
return NO;

return YES;
}

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
}
}

Other answers do not handle the case where user can paste a long string from clipboard. If I paste a long string it should just be truncated but shown.
Use this in your delegate:

static const NSUInteger maxNoOfCharacters = 5;

-(IBAction)textdidChange:(UITextField * )textField
{
NSString * text = textField.text;

if(text.length > maxNoOfCharacters)
{
text = [text substringWithRange:NSMakeRange(0, maxNoOfCharacters)];
textField.text = text;
}

// use 'text'

}

This is the correct way to handle max length on UITextField, it allows the return key to exit the resign the textfield as first responder and lets the user backspace when they reach the limit

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
int MAX_LENGHT = 5;
if([string isEqualToString:@"\n"])
{
[textField resignFirstResponder];
return FALSE;
}
else if(textField.text.length > MAX_LENGHT-1)
{
if([string isEqualToString:@""] && range.length == 1)
{
return TRUE;
}
else
{
return FALSE;
}
}
else
{
return TRUE;
}
}

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!

<br><br><br><br>
________
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));
}