仅允许textField中的字母表

Question

我想让UITextField只接受字符并在输入数字或特殊字符时显示错误.但是当我这样做时,当我输入字母时也会显示错误.不明白我哪里出错了？

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;
    }

现在,当我给出字母表时,也会显示错误.Y是这样的吗？

Answer 1

创建一个验证方法,如下所示:

-(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;
}

现在检查您想要的验证如下:

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

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

Answer 2

您可以使用以下代码验证字母表字符串.

运用 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]; 
}

运用 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;
 }