@Host装饰器如何在注入器树中工作

Question

我正在尝试了解 @Host 装饰器如何工作 与视图组件分离 。所以我创建了以下注入器树：

class Dependency {
}

@Injectable()
class NeedsDependency {
  constructor(@Host() public dependency: Dependency) {
    console.log(this.dependency); // outputs 'A', but I expected the error
  }
}

const parent = ReflectiveInjector.resolveAndCreate([{provide: Dependency, useValue: 'A'}]);
const child = parent.resolveAndCreateChild([]);
const grandchild = child.resolveAndCreateChild([NeedsDependency]);
grandchild.get(NeedsDependency);

我预计会出现错误，因为据我了解 grandchild 注入器的主机是 child，并且 child 注入器中没有提供 Dependency .但是，当我运行这段代码时，我从根注入器中注入了 'A' 。为什么？

Answer 1

Specifies that an injector should retrieve a dependency from any injector until reaching the host element of the current component.

https://angular.io/docs/ts/latest/api/core/index/Host-decorator.html

在我看来它会寻找提供者并在它到达组件的注入器后停止寻找。

Answer 2

Host 在普通 ReflectiveInjector.resolveAndCreate 注入器的上下文中没有语义意义。

It is just ignored 在编译器外部使用时。

对于所需的行为，

I expected to get an error, because as I understand the host for grandchild injector is child, and there is no Dependency provided in the child injector.

考虑改用 Self。

@Host装饰器如何在注入器树中工作

How does @Host decorator work in injector tree

javascript

angular2-di

angular