Allowing only alphabets in textField

问题

I want to make a UITextField to accept only characters and display error when numbers or special characters are entered.But when Im doing so ,when I enter alphabets also error is displayed.Could not understand where I going wrong?

NSString *FNameReg=@"[A-Za-z]";
NSPredicate *FNametest=[NSPredicate predicateWithFormat:@"SELF MATCHES %@",FNameReg];
 if(![FNametest evaluateWithObject:txtfirstname.text])
    {
        lblvalidateFName.hidden=NO;
        [testScroll setContentOffset:CGPointMake( 0 , 74)];
        return;
    }

BUt now when I give alphabets also then also error is displayed.Y is it so ?

回答1:

Create one method for validation like this:

-(BOOL) validateAlphabets: (NSString *)alpha
{
NSString *abnRegex = @"[A-Za-z]+"; // check for one or more occurrence of string you can also use * instead + for ignoring null value 
NSPredicate *abnTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", abnRegex];
BOOL isValid = [abnTest evaluateWithObject:alpha];
return isValid;
}

Now check for the validation where you want like this:

bool checkAlphabets = [self validateAlphabets:txtfirstname.text];

if(!checkAlphabets)
{
   NSLog(@"Not Matches..");
}
else
{
  NSLog(@"Matches..");
}

回答2:

You can validate the alphabet string with below code.

Using NSPredicate

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

    return [self validateStringWithAlphabet:string]; 
}

- (BOOL)validateStringWithAlphabet:(NSString *)string {
    NSString *stringRegex = @"[A-Za-z]";
    NSPredicate *stringPredicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", stringRegex];

    return [stringPredicate evaluateWithObject:string]; 
}

Using NSCharacterSet

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
 {
        if(textField == yourTextField)
        {
            NSCharacterSet *invalidCharSet = [[NSCharacterSet characterSetWithCharactersInString:@"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"] invertedSet];
            NSString *filtered = [[string componentsSeparatedByCharactersInSet:invalidCharSet] componentsJoinedByString:@""];
            return [string isEqualToString:filtered];
        }

        return YES;
 }

回答3:

try below code my friend , if you want to allow only alphabets.

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{

   NSCharacterSet *nonNumberSet = [[NSCharacterSet characterSetWithCharactersInString:@"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"] invertedSet];

   NSString *trimmedReplacement = [[ text componentsSeparatedByCharactersInSet: nonNumberSet] componentsJoinedByString:@""];

   return ([text stringByTrimmingCharactersInSet:nonNumberSet].length > 0); 

}

let me know it is working or not!!!!

Happy Coding!!!!!

回答4:

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

NSCharacterSet *blockedCharacters = [[NSCharacterSet whitespaceCharacterSet] invertedSet]; NSCharacterSet *blockedCharacters2 = [[NSCharacterSet letterCharacterSet]invertedSet]; 

if([string rangeOfCharacterFromSet:blockedCharacters].location == NSNotFound || [string rangeOfCharacterFromSet:blockedCharacters2].location)
{

 // enter your alert 
[alert show];
}
return ([string rangeOfCharacterFromSet:blockedCharacters].location == NSNotFound || [string rangeOfCharacterFromSet:blockedCharacters2].location) ;

}

回答5:

Check this out . First if block for backspace , next if to allow only letters , next if to allow only numbers.

  - (BOOL)textField:(UITextField *)field shouldChangeCharactersInRange:(NSRange)range       replacementString:(NSString *)characters
 {
NSCharacterSet *blockedCharacters = [[NSCharacterSet alphanumericCharacterSet] invertedSet] ;
NSCharacterSet *letters = [NSCharacterSet letterCharacterSet]  ;
NSCharacterSet *numbers = [NSCharacterSet decimalDigitCharacterSet]  ;

NSLog(@"%@",[blockedCharacters description]);

//for allowing backspace.
if([characters isEqualToString:@""])
{
    return true;
}
if(field==self.firstNameTextField || field==self.lastNameTextField || field==self.addrLocalityTextField || field==self.addrRegionField){


    if([characters rangeOfCharacterFromSet:letters].location) {
        [self shakeWithIterations:0 direction:1 size:4 view:field];

        return false;
    }
}

if(field==self.addrPostalCodeTextField || field==self.accountNumTextField || field==self.routingNumTextField ){

    if( field==self.addrPostalCodeTextField ){
    NSUInteger newLength = [addrPostalCodeTextField.text length] + [characters length] - range.length;
    return (newLength > 5) ? NO : YES;
    }
    if([characters rangeOfCharacterFromSet:numbers].location) {
        [self shakeWithIterations:0 direction:1 size:4 view:field];
        return false;
    }
}
 return true;}

来源：https://stackoverflow.com/questions/14358309/allowing-only-alphabets-in-textfield

标签

iphone

uitextfield

xcode4.5