什么是PageSlotComponent

解决方案

理论依据

In Angular you can inject the closest parent component of a given type, by passing it as a constructor dependency.

You might want to add @Optional() decorator if you plan to use your component outside the content slot (i.e. as a static component). It will help avoid crashing app in the runtime, but will just resolve PageSlotComponent instance safely to null.

看一个运行时的例子：

Angular里可以很容易的通过依赖注入，在一个Component的构造函数里，注入其祖先引用作为依赖。这样，Component里就能访问其祖先实例上的数据。