Objective C IPhone Subclassing UITextField catch Value Changed - iphone

Question

I have subclassed UITextField so I can create some custom behaviours for it. Here are my classes:
DataboundTextField.h
#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
#import "TestEntities.h"
#interface DataboundTextField : UITextField <UITextFieldDelegate> {
NSString *valueMember;
NSString *displayValueMember;
ODataObject *boundEntity;
}
#property (nonatomic, retain) NSString *valueMember;
#property (nonatomic, retain) NSString *displayValueMember;
#property (nonatomic, retain) ODataObject *boundEntity;
-(void)SetupDataBinding:(ODataObject*)oDataEntity ValueMember:(NSString*)valMemberID DisplayValueMember:(NSString*)disValMember;
#end
DataboundTextField.m
#import "DataboundTextField.h"
#implementation DataboundTextField
#synthesize valueMember;
#synthesize displayValueMember;
#synthesize boundEntity;
-(id) initWithCoder:(NSCoder *)aDecoder{
if ((self = [super initWithCoder:aDecoder]))
{
self.delegate = self;
}
return self;
}
-(void)SetupDataBinding:(ODataObject*)oDataEntity ValueMember:(NSString*)valMemberID DisplayValueMember:(NSString*)disValMember{
}
-(BOOL) textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
return YES;
}
#end
How do I go about overriding the ValueChanged event? I cannot seem to catch it however I try. All I want to do is wack one of these subclassed Textfields on a view and catch that event and handle it.
Please help.
Thanks in advance

Answer 1

According to the documentation for UITextFieldDelegate, you can use
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
The text field calls this method whenever the user types a new character in the text field or deletes an existing character.
Make sure you set the delegate property of your UITextField:
- (id)init
{
if ((self = [super init]))
{
self.delegate = self;
}
}

Answer 2

This is what I have used to allow only certain characters, as well as how many characters are allowed for a textField:
- (BOOL)textField:(UITextField *)theTextField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
/* allow only these characters in the textField */
NSCharacterSet *myCharSet = [NSCharacterSet characterSetWithCharactersInString:#" abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890|:.#~_-+#!{}%*"];
for (int i = 0; i < [string length]; i++) {
unichar c = [string characterAtIndex:i];
if (![myCharSet characterIsMember:c]) {
return NO;
}
}
/* choose how many characters the textField can have */
NSUInteger newLength = [theTextField.text length] + [string length] - range.length;
return (newLength > 28) ? NO : YES;
}