Sail.js官方文檔閱讀筆記（五）——Actions and controllers

總述

Actions是Sails項目中對客戶端響應請求的部分，它是model和view的中間層，負責梳理業務邏輯。
Actions是項目中的路由，當客戶端請求一個URL時，將經由它執行邏輯並響應。

定義在何處

Actions通常定義在api/controllers目錄下。

Actions示例

Actions文件通常有兩種組織形式，actions2（推薦）和傳統的。
Actions2:

module.exports = {

   friendlyName: 'Welcome user',

   description: 'Look up the specified user and welcome them, or redirect to a signup page if no user was found.',

   inputs: {
      userId: {
        description: 'The ID of the user to look up.',
        // By declaring a numeric example, Sails will automatically respond with `res.badRequest`
        // if the `userId` parameter is not a number.
        type: 'number',
        // By making the `userId` parameter required, Sails will automatically respond with
        // `res.badRequest` if it's left out.
        required: true
      }
   },

   exits: {
      success: {
        responseType: 'view',
        viewTemplatePath: 'pages/welcome'
      },
      notFound: {
        description: 'No user with the specified ID was found in the database.',
        responseType: 'notFound'
      }
   },

   fn: async function ({userId}) {

      // Look up the user whose ID was specified in the request.
      // Note that we don't have to validate that `userId` is a number;
      // the machine runner does this for us and returns `badRequest`
      // if validation fails.
      var user = await User.findOne({ id: userId });

      // If no user was found, respond "notFound" (like calling `res.notFound()`)
      if (!user) { throw 'notFound'; }

      // Display a personalized welcome view.
      return {
        name: user.name
      };
   }
};

使用傳統的(req, res)方法來寫actions會減少代碼量，但使用actions2有如下好處：

• 代碼不必依賴於req和res，使其更容易抽象成helper
• 可以及早確定actions需要的請求參數名和類型，在action運行時可以自動驗證
• 不必仔細分析代碼就能知道action所有可能的輸出結果

傳統：

module.exports = async function welcomeUser (req, res) {

  // Get the `userId` parameter from the request.
  // This could have been set on the querystring, in
  // the request body, or as part of the URL used to
  // make the request.
  var userId = req.param('userId');

   // If no `userId` was specified, or it wasn't a number, return an error.
  if (!_.isNumeric(userId)) {
    return res.badRequest(new Error('No user ID specified!'));
  }

  // Look up the user whose ID was specified in the request.
  var user = await User.findOne({ id: userId });

  // If no user was found, redirect to signup.
  if (!user) {
    return res.redirect('/signup' );
  }

  // Display the welcome view, setting the view variable
  // named "name" to the value of the user's name.
  return res.view('welcome', {name: user.name});

}

Controllers

生成Sails最快的方式就是把actions組織到controllers文件中。例如：

module.exports = {
  login: function (req, res) { ... },
  logout: function (req, res) { ... },
  signup: function (req, res) { ... },
};

獨立actions

對於大型成熟的系統，獨立的actions可能是比controllers更好的方式。並非多個actions寫在一個文件中，而是每個action都有一個獨立的文件在api/controller目錄下。如：

api/
 controllers/
  user/
   login.js
   logout.js
   signup.js

保持“瘦”

和多數MVC框架一樣，controller都是很瘦的一層。因爲可重用的代碼通常會被移到helpers或者提取到modules中。這使得項目變複雜的過程中更容易維護。
有一個規則：當使用同樣代碼的地方達到3處，即可將其移入helper中。