Question

当我以下列方式创建新模型时：

//user.js file
module.exports = function (sequelize, DateTypes) {

return sequelize.define("user", {
    email: {
        type: DateTypes.STRING,
        allowNull: false,
        unique: true,
        validate: {
            isEmail: true
        }
    },
    password: {
        type: DateTypes.STRING,
        allowNull: false,
        validate: {
            len: [7, 100]
        }
    }
});
};

并进入我构建新数据库的db.js文件：

var Sequelize = require('sequelize');
var env = process.env.NODE_ENV || "development"; // established if you work in production or in development mode
var sequelize;

if (env == "production") {
    sequelize = new Sequelize(process.env.DATABASE_URL, {
        "dialect": "postgres",

    });
} else {
    var sequelize = new Sequelize(undefined, undefined, undefined, {
        'dialect': 'sqlite',
        'storage': __dirname + '/data/dev-todo-api.sqlite' // location where you create a new sqlite database 
    });
}

var db = {};

db.todo = sequelize.import(__dirname + "/models/todo.js");
db.user = sequelize.import(__dirname + "/models/user.js");
db.sequelize = sequelize; //contain a settings of database
db.Sequelize = Sequelize;

module.exports = db;

我不明白user.js如何知道sequelize（我作为参数插入module.exports）是sequelize包的实例，如果它位于另一个文件中？也许是因为sequelize.import('/user.js')导入了整个续集包？

Answer 1

请参阅sequelize.import的定义：

Sequelize.prototype.import = function(path) {
  // is it a relative path?
  if(Path.normalize(path) !== Path.resolve(path)){
    // make path relative to the caller
    var callerFilename = Utils.stack()[1].getFileName()
      , callerPath = Path.dirname(callerFilename);

    path = Path.resolve(callerPath, path);
  }

  if (!this.importCache[path]) {
    var defineCall = (arguments.length > 1 ? arguments[1] : require(path));
    if (typeof defineCall === 'object' && defineCall.__esModule) {
      // Babel/ES6 module compatability
      defineCall = defineCall['default'];
    }
    this.importCache[path] = defineCall(this, DataTypes);
  }

  return this.importCache[path];
};

实际上它在路径上调用require，然后使用sequelize实例作为其第一个参数调用结果。这就是结点，允许模块引用导入它的续集实例。

Answer 2

可能会有所帮助。这是我编译后的代码：

/**
 * Imports a model defined in another file
 *
 * Imported models are cached, so multiple calls to import with the same path will not load the file multiple times
 *
 * See https://github.com/sequelize/express-example for a short example of how to define your models in separate files so that they can be imported by sequelize.import
 * @param {String} path The path to the file that holds the model you want to import. If the part is relative, it will be resolved relatively to the calling file
 * @return {Model}
 */
import(path) {
  // is it a relative path?
  if (Path.normalize(path) !== Path.resolve(path)) {
    // make path relative to the caller
    const callerFilename = Utils.stack()[1].getFileName();
    const callerPath = Path.dirname(callerFilename);

    path = Path.resolve(callerPath, path);
  }

  if (!this.importCache[path]) {
    let defineCall = arguments.length > 1 ? arguments[1] : require(path);
    if (typeof defineCall === 'object') {
      // ES6 module compatibility
      defineCall = defineCall.default;
    }
    this.importCache[path] = defineCall(this, DataTypes);
  }

  return this.importCache[path];
}

怎么能＆＃34; sequelize.import（）＆＃34;从另一个文件导入模型？

2 个答案: