限制UITextField仅可以输入小数点后两位且全部为数字

//   -------协议方法--------
-(BOOL)textField:(UITextField*)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString*)string{
    //小数点只能一个
    if([string isEqualToString:@"."] && ([textField.text rangeOfString:@"."].location!=NSNotFound|| [textField.text isEqualToString:@""])) {
        return NO;
    }
    //退格
    if([string isEqualToString:@""]) {
        return YES;
    }
    // 首位输入0之后 只能输.或者退格
    if([textField.text isEqualToString:@"0"] && ![string isEqualToString:@"."]) {
        return NO;
    }
    //小数点后面长度不超过2位
    BOOL isHasDot = false;// 是否包含小数点
    if([textField.text rangeOfString:@"."].location != NSNotFound) {
        isHasDot = true;
    }
    if(isHasDot) {
        //小数点位置
        NSRange dotRange = [textField.text rangeOfString:@"."];
        if(range.location - dotRange.location>2) {
            [self showHint:@"仅允许输入到小数点后两位"];
            return NO;
        }
    }
    //只能输入数字
    if([string rangeOfString:@"."].location==NSNotFound) {
        NSRange range = [string rangeOfString:@"^[0-9]+$"options:NSRegularExpressionSearch];
        if(range.location==NSNotFound) {
            return NO;
        }
    }
    return YES;
}