我正在学习Sequelize的Loopback 4，并且对TypeORM有一定的经验。
我的问题是为什么在Loopback 4中这种关系没有约束。我见过https://loopback.io/doc/en/lb4/todo-list-tutorial-sqldb.html#specify-the-foreign-key-constraints-in-todo-model，但是我不明白为什么它不能自动执行，或者我做错了什么。
让我们来看一个示例，其中三个ORMS具有相同的模型：一个User模型，可以有许多Post：
User --* Post
续集：
用户：
const User = sequelize.define(
'User',
{
id: {
type: Sequelize.INTEGER,
autoIncrement: true,
primaryKey: true,
allowNull: false,
},
name: {
type: Sequelize.STRING,
},
},
{}
);
User.associate = function(models) {
User.hasMany(models.Post, { onDelete: 'CASCADE' });
};
帖子：
const Post = sequelize.define(
'Post',
{
id: {
type: Sequelize.INTEGER,
autoIncrement: true,
primaryKey: true,
allowNull: false,
},
title: {
type: Sequelize.STRING,
},
text: {
type: Sequelize.TEXT,
},
},
{}
);
Post.associate = function(models) {
Post.belongsTo(models.User, { onDelete: 'CASCADE' });
};
MYSQL结果：
CREATE TABLE IF NOT EXISTS `test_sequelize`.`Users` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
`name` VARCHAR(255) NULL DEFAULT NULL,
PRIMARY KEY (`id`))
ENGINE = InnoDB
AUTO_INCREMENT = 3
DEFAULT CHARACTER SET = utf8
COLLATE = utf8_unicode_ci;
CREATE TABLE IF NOT EXISTS `test_sequelize`.`Posts` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
`title` VARCHAR(255) NULL DEFAULT NULL,
`text` TEXT NULL DEFAULT NULL,
`UserId` INT(11) NULL DEFAULT NULL,
PRIMARY KEY (`id`),
INDEX `UserId` (`UserId` ASC) ,
CONSTRAINT `posts_ibfk_1`
FOREIGN KEY (`UserId`)
REFERENCES `test_sequelize`.`Users` (`id`)
ON DELETE CASCADE
ON UPDATE CASCADE)
ENGINE = InnoDB
AUTO_INCREMENT = 4
DEFAULT CHARACTER SET = utf8
COLLATE = utf8_unicode_ci;
好的，约束就在那里。
现在让我们尝试使用TypeORM：
TypeORM：
用户：
import { Post } from './Post';
@Entity()
export class User {
@PrimaryGeneratedColumn()
id: string;
@Column()
name: string;
@OneToMany(type => Post, post => post.user, { onDelete: 'CASCADE' })
posts: Post[];
}
帖子：
import { User } from './User';
import { PostHasTag } from './PostHasTag';
import { Tag } from './Tag';
@Entity()
export class Post {
@PrimaryGeneratedColumn()
id: number;
@Column()
title: string;
@Column({ type: 'text' })
text: string;
@ManyToOne(type => User, user => user.posts)
user: User;
}
这是MySQL中的结果：
CREATE TABLE IF NOT EXISTS `test_typeorm`.`user` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
`name` VARCHAR(255) NOT NULL,
PRIMARY KEY (`id`))
ENGINE = InnoDB
AUTO_INCREMENT = 3
DEFAULT CHARACTER SET = utf8
COLLATE = utf8_unicode_ci;
CREATE TABLE IF NOT EXISTS `test_typeorm`.`post` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
`title` VARCHAR(255) NOT NULL,
`text` TEXT NOT NULL,
`userId` INT(11) NULL DEFAULT NULL,
PRIMARY KEY (`id`),
INDEX `FK_5c1cf55c308037b5aca1038a131` (`userId` ASC) ,
CONSTRAINT `FK_5c1cf55c308037b5aca1038a131`
FOREIGN KEY (`userId`)
REFERENCES `test_typeorm`.`user` (`id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB
AUTO_INCREMENT = 4
DEFAULT CHARACTER SET = utf8
COLLATE = utf8_unicode_ci;
一切都很好，那里有限制。现在有了Loopback4。
环回4：
模型，存储库，控制器和关系是由cli生成的，但我只会发布模型：
用户：
import {Post} from './post.model';
@model({settings: {}})
export class User extends Entity {
@property({
type: 'number',
id: true,
generated: true,
})
id?: number;
@property({
type: 'string',
required: true,
})
name: string;
@hasMany(() => Post)
posts: Post[];
constructor(data?: Partial<User>) {
super(data);
}
}
export interface UserRelations {
// describe navigational properties here
}
export type UserWithRelations = User & UserRelations;
帖子：
import {Entity, model, property} from '@loopback/repository';
@model({settings: {}})
export class Post extends Entity {
@property({
type: 'number',
id: true,
generated: true,
})
id?: number;
@property({
type: 'string',
required: true,
})
title: string;
@property({
type: 'string',
})
text?: string;
@property({
type: 'number',
})
userId?: number;
constructor(data?: Partial<Post>) {
super(data);
}
}
export interface PostRelations {
// describe navigational properties here
}
export type PostWithRelations = Post & PostRelations;
和MySQL：
CREATE TABLE IF NOT EXISTS `test_loopback`.`Post` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
`title` VARCHAR(512) NOT NULL,
`text` VARCHAR(512) NULL DEFAULT NULL,
`userId` INT(11) NULL DEFAULT NULL,
PRIMARY KEY (`id`))
ENGINE = InnoDB
AUTO_INCREMENT = 2
DEFAULT CHARACTER SET = utf8
COLLATE = utf8_unicode_ci;
CREATE TABLE IF NOT EXISTS `test_loopback`.`User` (
`id` INT(11) NOT NULL AUTO_INCREMENT,
`name` VARCHAR(512) NOT NULL,
PRIMARY KEY (`id`))
ENGINE = InnoDB
AUTO_INCREMENT = 2
DEFAULT CHARACTER SET = utf8
COLLATE = utf8_unicode_ci;
您可能会看到，那里没有约束。难道我做错了什么？这是预期的行为吗？
答案 0 :(得分：0)
这是LoopBack的一个已知缺点，请参见以下GitHub问题中的讨论：
答案 1 :(得分：0)
Loopback 4和MySQL关系中的约束
@model({
settings: {
foreignKeys: {
fk_todo_todoListId: {
name: 'fk_todo_todoListId',
entity: 'TodoList',
entityKey: 'id',
foreignKey: 'todolistid',
},
},
},
})
export class Todo extends Entity {
//etc.
}