Loopback远程方法属性验证：min/max不生效如何解决？

我来帮你搞定这个验证规则不生效的问题～ 其实核心原因是Loopback的远程方法参数默认不会自动触发min/max这类验证规则，只有required是基础必填检查，所以它能正常工作。另外还要注意字符串和数字类型的验证规则是有区别的，我给你几个可行的解决方案：

方法一：用validation字段指定验证规则（Loopback 3适用） #

把你的min/max规则放到validation对象里，而且字符串类型的长度验证要改用minLength和maxLength（min/max是给数字类型用的）。修改后的配置如下：

{
  "name": "registration",
  "methods": {
    "registrationIn": {
      "accepts": [
        {
          "arg": "firstname",
          "type": "string",
          "required": true,
          "description": "Firstname of the person.",
          "http": { "source": "form" },
          "validation": {
            "minLength": 1,
            "maxLength": 25
          }
        },
        {
          "arg": "mobile",
          "type": "number",
          "required": true,
          "description": "",
          "http": { "source": "form" },
          "validation": {
            "min": 1,
            "max": 10
          }
        }
      ],
      "returns": [],
      "description": "This method used to registration.",
      "http": [{ "path": "/registrationIn", "verb": "post" }]
    }
  }
}

方法二：定义参数模型复用验证规则 #

这种方式更适合复杂的参数验证，也方便后续维护。先创建一个参数模型RegistrationInput（放在common/models/registration-input.json）：

{
  "name": "RegistrationInput",
  "base": "Model",
  "properties": {
    "firstname": {
      "type": "string",
      "required": true,
      "minLength": 1,
      "maxLength": 25,
      "description": "Firstname of the person."
    },
    "mobile": {
      "type": "number",
      "required": true,
      "min": 1,
      "max": 10
    }
  }
}

然后在远程方法配置里直接引用这个模型作为参数类型：

{
  "name": "registration",
  "methods": {
    "registrationIn": {
      "accepts": [
        {
          "arg": "data",
          "type": "RegistrationInput",
          "required": true,
          "http": { "source": "form" }
        }
      ],
      "returns": [],
      "description": "This method used to registration.",
      "http": [{ "path": "/registrationIn", "verb": "post" }]
    }
  }
}

这样模型里的所有验证规则都会自动应用到远程方法的参数上，非常省心。

方法三：手动在方法实现里添加验证 #

如果上面两种方式都不适用，你可以直接在远程方法的代码里手动检查参数，然后抛出错误：

module.exports = function(Registration) {
  Registration.registrationIn = function(firstname, mobile, callback) {
    // 验证用户名长度
    if (!firstname || firstname.length < 1 || firstname.length > 25) {
      return callback(new Error('Firstname must be between 1 and 25 characters.'));
    }
    // 验证手机号范围
    if (mobile < 1 || mobile > 10) {
      return callback(new Error('Mobile number must be between 1 and 10 digits.'));
    }
    // 这里写你的业务逻辑
    callback(null);
  };

  // 别忘了注册远程方法的配置
  Registration.remoteMethod('registrationIn', {
    accepts: [
      { arg: 'firstname', type: 'string', required: true, http: { source: 'form' } },
      { arg: 'mobile', type: 'number', required: true, http: { source: 'form' } }
    ],
    returns: [],
    http: [{ path: '/registrationIn', verb: 'post' }]
  });
};

内容的提问来源于stack exchange，提问作者uday214125