UITextField只允许英文字母输入

Question

我想限制输入为用户名字段的英文字母（a-z）。有人可以帮助我添加下面的代码，不允许输入任何数字，字符和任何其他语言，而不是英文字母吗？

现在下面的代码不允许使用空格，也不允许输入超过10个字母。

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string { 
{ 
    BOOL _isAllowed = YES; 
    NSString *nameRegex = @"[A-Za-z]+"; 
    NSPredicate *nameTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", nameRegex]; 

    NSString *tempString = [[textField.text stringByReplacingCharactersInRange:range withString:string] stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]]; 



    if (textField == self.usernameField) 
    { 
     if ([self.usernameField.text isEqualToString:tempString]) 
     { 
      self.title.text = @"No Spaces Allowed"; 
      self.title.textColor = [UIColor yellowColor]; 

      _isAllowed = NO; 
     } 

     else if (tempString.length > 10) 
     { 
      self.title.text = @"Username cannot be more than 10 letters."; 
      self.title.textColor = [UIColor yellowColor]; 

      _isAllowed = NO; 
     } 

修订：

 else if (![nameTest evaluateWithObject:self.usernameField.text]) 
     { 
       self.title.text = @"Username can only contain english letters."; 
       self.title.textColor = [UIColor yellowColor]; 

       _isAllowed = NO; 
     } 
     return _isAllowed; 
    } 

    return _isAllowed; 
} 

感谢。

Answer 1

你可以使用这个表达式来检查用户名只包含英文字母：

NSString *nameRegex = @"[A-Za-z]+"; 
NSPredicate *nameTest = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", nameRegex]; 

if(![nameTest evaluateWithObject:self.usernameField.text]){ 
     self.title.text = @"Username can only contain english letters."; 
     self.title.textColor = [UIColor yellowColor]; 

     _isAllowed = NO; 
}