iOS中UITextField限制只能输入金额格式

iOS只能输入数字与一个小数点，金额输入框。

//限制只能输入金额
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{
    //首先设置：inputTF.keyboardType = UIKeyboardTypeDecimalPad;
    
    NSString * toBeString = [textField.text stringByReplacingCharactersInRange:range withString:string];
    //限制.后面最多有两位，且不能再输入.
    if ([textField.text rangeOfString:@"."].location != NSNotFound) {
        //有.了 且.后面输入了两位  停止输入
        if (toBeString.length > [toBeString rangeOfString:@"."].location+3) {
            return NO;
        }
        //有.了，不允许再输入.
        if ([string isEqualToString:@"."]) {
            return NO;
        }
    }
    
    //限制首位0，后面只能输入. 或 删除
    if ([textField.text isEqualToString:@"0"]) {
        if (!([string isEqualToString:@"."] || [string isEqualToString:@""])) {
            return NO;
        }
    }
    
    //首位. 前面补全0
    if ([toBeString isEqualToString:@"."]) {
        textField.text = @"0";
        return YES;
    }
    
    //限制只能输入：1234567890.
    NSCharacterSet * characterSet = [[NSCharacterSet characterSetWithCharactersInString:@"1234567890."] invertedSet];
    NSString * filtered = [[string componentsSeparatedByCharactersInSet:characterSet] componentsJoinedByString:@""];
    return [string isEqualToString:filtered];
}