egg-sequelize 定义关联关系

定义关联关系

app/mode/xxx.js 中通过给模型（类）添加associate 属性，属性值为一个function(){}，方法中执行sequelize提供的建立关联关系的方法，例如 belongsTo等

egg-sequelize 插件在loadDatabase的时候会执行associate()，建立模型之间的关系

module.exports = app => {
    const { BIGINT, STRING } = app.Sequelize;
    const User = app.model.define('users', {
        id: {
            type: BIGINT,
            primaryKey: true,
            autoIncrement: true,
        },
       team_id: BIGINT,
       name: STRING,
    });
    User.associate = function () {
        app.model.User.belongsTo(app.model.Team, { foreignKey: 'team_id' });
    };
    return User;
};

sequelize V4版本修改了建立关系的方式：

Removed classMethods and instanceMethods options from sequelize.define. Sequelize models are now ES6 classes. You can set class / instance level methods like this

const Model = sequelize.define('Model', {
    ...
});

// Class Method
Model.associate = function (models) {
    ...associate the models
};

// Instance Method
Model.prototype.someMethod = function () {..}

执行数据库操作，例如 findAll 的时候，如果 include 了 model，执行之前会检测 model 之间的关联关系。如果没有提前定义，则报错 ${targetModel.name} is not associated to ${this.name}!