在Angular 4 Dart中获取ComponentFactory的最佳方法是什么？

Question

There is documentation in the AngularDart Github repo for Component loading ( https://github.com/dart-lang/angular/blob/master/doc/component_loading.md ) that recommends importing a component's template file (which is generated) and then accessing a property on that template where you just take the component's name and append NgFactory to it.

import 'foo.template.dart' as ng;

void doSomething() {
  ng.FooComponentNgFactory;
  //             ^^^^^^^^^
}

But my IDE (IntelliJ) can't see foo.template.dart as it has not been generated yet and gives me warnings and then it also knows nothing about the FooComponentNgFactory . With Dart being dynamic, this all works out at runtime, but it leaves me with warnings / errors in my IDE which I don't want to be in the habit of having to ignore and the whole thing feels like a code smell to me.

I was also able to get a factory by using a ComponentResolver, which did not involve needing to use the generated template files, or NgFactory . The only downside that I can see is that it is an async method, which in my case is not a problem.

@Component(selector: 'some-component', template: '')
class SomeComponent {
  SomeComponent(this._resolver);

  ComponentResolver _resolver;

  Future doSomething() async {
    ComponentFactory factory = await _resolver.resolveComponent(FooComponent);
  }
}

In looking at ComponentResolver's documentation I don't see any reason not to use it ( https://webdev.dartlang.org/api/angular/angular/ComponentResolver-class ).

Why is this not the accepted way to get a ComponentFactory? Am I doing something wrong with the NgFactory or is there something that I need to be careful with using ComponentResolver that I'm missing?

Answer 1

There are two reasons we don't want to use resolver:

• It needs a mapping between the Component Type and the Factory. With this map Dart2JS doesn't know if this code is being used and it can't be tree shaken. Currently any imported Component is in our end executables even when we don't use them.
• We can make it a tiny bit faster by not needing an async action.

Tree shaking is the big reason though.