判断输入的是纯数字还是纯字母的方法

//判断是否是纯字母
- (BOOL)isPureCharacters:(NSString *)string
{
    string = [string stringByTrimmingCharactersInSet:[NSCharacterSet letterCharacterSet]];
    if(string.length > 0)
    {
        return NO;
    }
    return YES;
}

//判断是否是纯数字
- (BOOL)isPureNum:(NSString *)string
{
    string = [string stringByTrimmingCharactersInSet:[NSCharacterSet decimalDigitCharacterSet]];
    if(string.length > 0)
    {
        return NO;
    }
    return YES;
}

//判断是否包含连续的数组或字母，yes为包含
- (BOOL)rangeString:(NSString *)string {

    BOOL result = NO;
    
    for (int i = 0; i < string.length; i++) {
        
        if (string.length - i < 4 ) {
            break;
        }
        
        NSString *newStr = [string substringWithRange:NSMakeRange(i, 4)];
        
        if ([self isPureCharacters:newStr] || [self isPureNum:newStr]) {
            NSLog(@"%@",newStr);
            result = YES;
            break;
        }
    }
    return result;
}