Limit textfield input to 30 characters

[samsecke]

All,
Is there a way to impose character limit on a textfield? I would like to limit a textfield input to 30 characters.
I can achieve this programmatically, but wanted to know if it’s achievable through Object Library (Like Number Formatter for e.g.)

[DJ_Bazzie_Wazzie]

@samsecke

All,
Is there a way to impose character limit on a textfield? I would like to limit a textfield input to 30 characters.
I can achieve this programmatically, but wanted to know if it’s achievable through Object Library (Like Number Formatter for e.g.)

Best way is using a subclass of NSFormatter and implement the isPartialStringValid method. The partialString (first) argument is the new string. If it length of the new string exceeds the maximum field length return false and the character will not be inserted into the text field; otherwise return true.

[samsecke]

@DJ Bazzie Wazzie

Best way is using a subclass of NSFormatter and implement the isPartialStringValid method. The partialString (first) argument is the new string. If it length of the new string exceeds the maximum field length return false and the character will not be inserted into the text field; otherwise return true.

How do I use the NSFormatter Class? Do I just drag this from the Object Library onto the Text Field Cell? How do I call the isPartialStringValid of this class?

[fiz]

Hello samsecke,

The is a method of NSString which returns the length as a NSUInteger. You could write a “LimitedEntryFormatter” (a subclass of NSFormatter) with the method pointed by DJ, so:

@implementation LimitedEntryFormatter

• (BOOL)isPartialStringValid:(NSString **)partialString
  proposedSelectedRange:(NSRangePointer)proposedSelRange
  originalString:(NSString *)origString
  originalSelectedRange:(NSRange)origSelRange
  errorDescription:(NSString **)error
  {
  if([partialString lenght] >30) return NO;
  return YES;
  }
  @end

Choose “New > File.”, then Objective-C class, give the name “LimitedEntryFormatter”, make it a subclass of NSFormatter, paste this code into the .m file, and in IB, drag a NSFormatter to your text field, set its class to your new class, and try to enter text.

Hope this helps.

[DJ_Bazzie_Wazzie]

@interface lengthFormatter : NSFormatter {}
@end

@implementation lengthFormatter

• (BOOL)isPartialStringValid:(NSString **)partialString
  proposedSelectedRange:(NSRangePointer)proposedSelRange
  originalString:(NSString *)origString
  originalSelectedRange:(NSRange)origSelRange
  errorDescription:(NSString **)error
  {
  if([*partialString length] >30) //change to the preffered length
  return NO;
  return YES;
  }

• (NSString *)stringForObjectValue:(id)object {
  return (NSString *)object; //no conversions here
  }

• (BOOL)getObjectValue:(id *)object forString:(NSString *)string errorDescription:(NSString **)error {
  *object = string; //Edited later
  return YES;
  }
  @end

To set the formatter in AppleScriptObjC:

set myFormatter to current application's class "lengthFormatter"'s alloc()'s init()
myTextField's |cell|()'s setFormatter_(myFormatter)

fiz forgot to implement the required stringForObjectValue and getObjectValue methods. Those are required methods when you subclass an NSFormatter.

[samsecke]

Thanks Fiz and DJ. I was able to extend this class so that it can accept any length. Here is my implementation:

@interface LengthFormatter : NSFormatter {
int maxLength;
}
-(void) setMaxLength: (int) n;
@end

@implementation LengthFormatter

• (BOOL)isPartialStringValid:(NSString **)partialString
  proposedSelectedRange:(NSRangePointer)proposedSelRange
  originalString:(NSString *)origString
  originalSelectedRange:(NSRange)origSelRange
  errorDescription:(NSString **)error
  {
  if([*partialString length] > maxLength) //change to the preffered length
  return NO;
  return YES;
  }

-(void) setMaxLength: (int) n {
maxLength = n;
}

-(int) maxLength {
return maxLength;
}

• (NSString *)stringForObjectValue:(id)object {
  return (NSString *)object; //no conversions here
  }

• (BOOL)getObjectValue:(id *)object forString:(NSString *)string errorDescription:(NSString **)error {
  return YES;
  }
  @end

To set the formatter in AppleScriptObjC for 2 fields , each having different character limits:

on applicationWillFinishLaunching_(aNotification)
set Field1Formatter to current application's class "LengthFormatter"'s alloc()'s init()
        Field1Formatter's setMaxLength_(5)
        Field1's |cell|()'s setFormatter_(Field1Formatter)

set Field2Formatter to current application's class "LengthFormatter"'s alloc()'s init()
        Field2Formatter's setMaxLength_(10)
        Field2's |cell|()'s setFormatter_(Field2Formatter)
end applicationWillFinishLaunching_

The only issue currently is that after typing in field1/field2 and then going to a different field, the typed text disappears. Any idea why this is happening? Did I miss something?

[fiz]

Hello,

I got the same issue, try this:

-(NSString*) stringForObjectValue:(id)object {
if( ![object isKindOfClass: [ NSString class ] ] ) {
return nil;
}
return [ NSString stringWithString: object ];
}

[samsecke]

@fiz

Hello,

I got the same issue, try this:

-(NSString*) stringForObjectValue:(id)object {
if( ![object isKindOfClass: [ NSString class ] ] ) {
return nil;
}
return [ NSString stringWithString: object ];
}

Didn’t work for me. I still have the same issue

[Shane_Stanley]

@DJ Bazzie Wazzie

• (BOOL)getObjectValue:(id *)object forString:(NSString *)string errorDescription:(NSString **)error {
  return YES;
  }

DJ,

Aren’t you missing an “*obj = string;” in there?

[samsecke]

@Shane Stanley

@DJ Bazzie Wazzie

• (BOOL)getObjectValue:(id *)object forString:(NSString *)string errorDescription:(NSString **)error {
  return YES;
  }

DJ,

Aren’t you missing an “*obj = string;” in there?

Thanks Shane,
That did the trick

[DJ_Bazzie_Wazzie]

@Shane Stanley

@DJ Bazzie Wazzie

• (BOOL)getObjectValue:(id *)object forString:(NSString *)string errorDescription:(NSString **)error {
  return YES;
  }

DJ,

Aren’t you missing an “*obj = string;” in there?

Correct shane… I don’t know why I missed that and also my test projects (for this topic) works like a charm. But nevertheless it should always be in there, even if if you don’t make any coercions.