使用UITextField自动格式化银行卡号

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {  
  
   NSString *text = [textField text];  
  
    NSCharacterSet *characterSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789\b"];  
    string = [string stringByReplacingOccurrencesOfString:@" " withString:@""];  
    if ([string rangeOfCharacterFromSet:[characterSet invertedSet]].location != NSNotFound) {  
        return NO;  
    }  
  
    text = [text stringByReplacingCharactersInRange:range withString:string];  
    text = [text stringByReplacingOccurrencesOfString:@" " withString:@""];  
  
    NSString *newString = @"";  
    while (text.length > 0) {  
        NSString *subString = [text substringToIndex:MIN(text.length, 4)];  
        newString = [newString stringByAppendingString:subString];  
        if (subString.length == 4) {  
            newString = [newString stringByAppendingString:@" "];  
        }  
        text = [text substringFromIndex:MIN(text.length, 4)];  
    }  
  
    newString = [newString stringByTrimmingCharactersInSet:[characterSet invertedSet]];  
  
    if (newString.length >= 20) {  
        return NO;  
    }  
  
    [textField setText:newString];  
  
    return NO;  
}

// 16位以内 (3个空格)  
        NSString *str_bangNum = [NSString stringWithFormat:@"%@%@",textField.text,string];  
        if (textField.text.length < 23) {  
            //银行卡只能输入数字  
            cs = [[NSCharacterSet characterSetWithCharactersInString:NUMBERS] invertedSet];  
            NSString *filterStr = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];  
            BOOL basicTest = [string isEqualToString:filterStr];  
            if(!basicTest)  
            {  
                return NO;  
            }  
              
            //显示内容的格式化  
            if(range.length > 0 && str_bangNum.length > 0)// 支持删除  
            {  
                NSString *tmp_str = [str_bangNum bankNumToNormalNum];  
                str_bangNum = [tmp_str substringToIndex:(tmp_str.length - 1)];  
            }  
            str_bangNum = [str_bangNum normalNumToBankNum];  
            textField.text = str_bangNum;  
            return NO;  
        }  
        else  
        {  
            if(range.length > 0 && str_bangNum.length > 0)// 支持删除  
            {  
                NSString *tmp_str = [str_bangNum bankNumToNormalNum];  
                str_bangNum = [tmp_str substringToIndex:(tmp_str.length - 1)];  
                str_bangNum = [str_bangNum normalNumToBankNum];  
                textField.text = str_bangNum;  
            }  
            return NO;  
        }

// 正常号转银行卡号 － 增加4位间的空格  
-(NSString *)normalNumToBankNum  
{  
     NSString *tmpStr = [self bankNumToNormalNum];  
      
    int size = (tmpStr.length / 4);  
     
    NSMutableArray *tmpStrArr = [[NSMutableArray alloc] init];  
    for (int n = 0;n < size; n++)  
    {  
        [tmpStrArr addObject:[tmpStr substringWithRange:NSMakeRange(n*4, 4)]];  
    }  
      
    [tmpStrArr addObject:[tmpStr substringWithRange:NSMakeRange(size*4, (tmpStr.length % 4))]];  
      
    tmpStr = [tmpStrArr componentsJoinedByString:@" "];  
  
    return tmpStr;  
}  
  
// 银行卡号转正常号 － 去除4位间的空格  
-(NSString *)bankNumToNormalNum  
{  
    return [self stringByReplacingOccurrencesOfString:@" " withString:@""];  
}