定义以下变量

#define NUMBERS @"0123456789"
#define ALPHABATES @"ABCDEFGHIJKLMNOPQRSTUVWXYZ"

现在在文本字段的委托函数中，

Now in the delegate function of the textfield,

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    NSCharacterSet *cs;
    NSString *filtered;
    //for maximum characters
    if (textField.text.length >= 11 && range.length == 0)
        return NO;

    if(textField.text.length<11)
    {
        NSString *cStr=[NSString stringWithFormat:@"%@%@",textField.text,string];
        if([cStr length]<11)
        {
            if(range.location<4)
            {

                cs = [[NSCharacterSet characterSetWithCharactersInString:ALPHABATES] invertedSet];
                filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
                return [string isEqualToString:filtered];
            }
            else
            {

                cs = [[NSCharacterSet characterSetWithCharactersInString:NUMBERS] invertedSet];
                filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
                return [string isEqualToString:filtered];
            }
        }
        else
        {
            int iPrevLength,iNextLength;
            iPrevLength=[textField.text length];
            iNextLength=11;
            int iLengthDiff=iNextLength-iPrevLength;
            string=[string substringToIndex:iLengthDiff];
            if(range.location<4)
            {

                cs = [[NSCharacterSet characterSetWithCharactersInString:ALPHABATES] invertedSet];
                filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
                return [string isEqualToString:filtered];
            }
            else
            {

                cs = [[NSCharacterSet characterSetWithCharactersInString:NUMBERS] invertedSet];
                filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
                return [string isEqualToString:filtered];
            }
            if([string isEqualToString:filtered])
            textField.text=[NSString stringWithFormat:@"%@%@",textField.text,string];
            return NO;
        }
    }

    return YES;
}

确保 ALPHABATES 有大写字母，所以它只适用于大写字母，如 A,B C 而不是 a,b,c....

Make sure as ALPHABATES has capital letters so it will only work for the caps letter like A,B C not a,b,c....

它首先接受 ALPHABATES 的 4 个字母，然后接受 NUMBERS 的 6-7 个字母.

It first accept the 4 letter of ALPHABATES then 6-7 letters of NUMBERS.

希望它对你有用.

告诉我.