Angular2中的依赖注入-TypeScript语法与@Inject

Question

I'm using Angular2 build 2.0.0-alpha.34 and I'm not sure why these two different pieces of code are giving me different results.

The only difference is using @Inject(TitleService) titleService vs using titleService: TitleService

This correctly works (ES2015 way)

import {Inject, Component, View, bootstrap, NgFor} from 'angular2/angular2';
import {titleComponent} from './components/title';
import {TitleService} from './services/services';

// Annotation section
@Component({
    selector: 'my-app'
})
@View({
    templateUrl: './html/app.html',
    directives: [titleComponent, NgFor]
})
// Component controller
class MyAppComponent {
    titles: Array<Object>;
    constructor(@Inject(TitleService) titleService) {
        console.log(titleService)
        this.titles = titleService.getTitles();
    }
}

bootstrap(MyAppComponent,[TitleService]); 

This doesn't work (TypeScript way), it doesn't ever make it to the console.log call in constructor, but it doesn't throw an error

import {Inject, Component, View, bootstrap, NgFor} from 'angular2/angular2';
import {titleComponent} from './components/title';
import {TitleService} from './services/services';

// Annotation section
@Component({
    selector: 'my-app'
})
@View({
    templateUrl: './html/app.html',
    directives: [titleComponent, NgFor]
})
// Component controller
class MyAppComponent {
    titles: Array<Object>;
    constructor(titleService: TitleService) {
        console.log(titleService)
        this.titles = titleService.getTitles();
    }
}

bootstrap(MyAppComponent,[TitleService]); 

If I'm using TypeScript's way to inject, do I need to do something else somewhere?

Answer 1

You need to add it in the viewBindings of your Component annotation :

viewBindings: [TitleService]

Note that you only need to do it once, say in the Root component and every other component within the hierarchy will get it injecting from the root component, as if the component's injector can't resolve the dependency it goes up until it finds it. If you define one viewBindings you should have the same instance everywhere I believe.

edit: renaming of parameter in alpha 34.

Answer 2

I had TitleService defined in a JavaScript file, using an ES2015 class, I just needed to change it to a TypeScript file so it compiled correctly. Oops.