sequelize.js - Sequelize中定义belongsTo关系时as和foreignKey的区别

Question

考虑以下来自 Sequelize documentation 的片段

class User extends Model {}
User.init({/* attributes */}, { sequelize, modelName: 'user' })
class UserRole extends Model {}
UserRole.init({/* attributes */}, { sequelize, modelName: 'userRole' });

之间有什么区别

User.belongsTo(UserRole, {as: 'role'}); // Adds roleId to user rather than userRoleId to User

和

User.belongsTo(UserRole, {foreignKey: 'roleId'}); // Adds roleId to user rather than userRoleId to User

为什么有人会写

User.belongsTo(UserRole, {foreignKey: 'roleId', as: 'fk_user_role'});

Answer 1

User.belongsTo(UserRole, {foreignKey: 'roleId', as: 'fk_user_role'});

as: 'fk_user_role' 用作别名来区分某个模型与另一个模型的关联，该模型已创建多次。
例如:

User.belongsTo(Organization, {foreignKey: 'organizationId', as: 'Organization'});
User.belongsTo(Organization, {foreignKey: 'headOrganizationId', as: 'HeadOrganization'});
...
User.findOne({
where: { 
  id: userId
},
include: [{
  model: Organization,
  as: 'Organization'
}, {
  model: Organization,
  as: 'HeadOrganization'
}]
})

你会得到一个带有 Organization 和 HeadOrganization Prop 的用户对象。