如何在环回 4 上实现自引用模型，而无需获取循环依赖项

Question

我在环回 4 项目上创建了一个名为Lot的新模型。批次可以有子批次(即Lot的实例(。 我添加了与 cli 的关系，但是当我使用POSTLotLotController方法创建新的子地块时，出现此错误：

Unhandled error in POST /lots/1/lots: 500 Error: Circular dependency detected: controllers.LotLotController --> @LotLotController.constructor[0] --> repositories.LotRepository --> @LotRepository.constructor[1] --> repositories.LotRepository
at ResolutionSession.pushBinding (/path/to/my/project/node_modules/@loopback/context/src/resolution-session.ts:251:13)
at Function.enterBinding (/path/to/my/project/node_modules/@loopback/context/src/resolution-session.ts:97:13)
at Function.runWithBinding (/path/to/my/project/node_modules/@loopback/context/src/resolution-session.ts:112:49)
at Binding.getValue (/path/to/my/project/node_modules/@loopback/context/src/binding.ts:332:40)
at RequestContext.getValueOrPromise (/path/to/my/project/node_modules/@loopback/context/src/context.ts:762:32)
at RequestContext.get (/path/to/my/project/node_modules/@loopback/context/src/context.ts:572:17)
at DefaultHasManyRepository.getter [as getTargetRepository] (/path/to/my/project/node_modules/@loopback/context/src/inject.ts:426:16)
at DefaultHasManyRepository.create (/path/to/my/project/node_modules/@loopback/repository/src/relations/has-many/has-many.repository.ts:79:41)
at LotLotController.create (/path/to/my/project/packages/server/src/controllers/lot-lot.controller.ts:68:43)
at invokeTargetMethod (/path/to/my/project/node_modules/@loopback/context/src/invocation.ts:255:47)
at value_promise_1.transformValueOrPromise.args (/path/to/my/project/node_modules/@loopback/context/src/invocation.ts:232:12)
at Object.transformValueOrPromise (/path/to/my/project/node_modules/@loopback/context/src/value-promise.ts:270:12)
at invokeTargetMethodWithInjection (/path/to/my/project/node_modules/@loopback/context/src/invocation.ts:227:10)
at InterceptedInvocationContext.invokeTargetMethod (/path/to/my/project/node_modules/@loopback/context/src/invocation.ts:118:14)
at targetMethodInvoker (/path/to/my/project/node_modules/@loopback/context/src/interceptor.ts:341:23)
at value_promise_1.transformValueOrPromise.fn (/path/to/my/project/node_modules/@loopback/context/src/interceptor-chain.ts:175:14)

实际上，控制器依赖于现在对自身的LotRepository：

constructor(
@inject('datasources.db') dataSource: DbDataSource,
@repository.getter('LotRepository')
protected lotRepositoryGetter: Getter<LotRepository>,
@repository.getter('ItemRepository')
protected itemRepositoryGetter: Getter<ItemRepository>,
) {
super(Lot, dataSource);
this.items = this.createHasManyRepositoryFactoryFor(
'items',
itemRepositoryGetter,
);
this.registerInclusionResolver('items', this.items.inclusionResolver);
this.subLots = this.createHasManyRepositoryFactoryFor(
'subLots',
lotRepositoryGetter,
);
this.registerInclusionResolver('subLots', this.subLots.inclusionResolver);
}

我怎样才能避免这种情况？ 谢谢

Answer 1

你必须改变你创建的方式有很多关系。试试这个：

constructor(
@inject('datasources.db') dataSource: DbDataSource,
@repository.getter('ItemRepository')
protected itemRepositoryGetter: Getter<ItemRepository>,
) {
super(Lot, dataSource);
this.items = this.createHasManyRepositoryFactoryFor(
'items',
itemRepositoryGetter,
);
this.registerInclusionResolver('items', this.items.inclusionResolver);
this.subLots = this.createHasManyRepositoryFactoryFor(
'subLots',
Getter.fromValue(this);
);
this.registerInclusionResolver('subLots', 
this.subLots.inclusionResolver);
}

(您必须从@loopback/核心导入的 Getter(。