发表于： 2021-03-18 21:36:11
1 1089
今天完成的事情：
Angular 中的依赖注入
依赖，是当类需要执行其功能时，所需要的服务或对象
在hero-list.component.ts中
export class HeroListComponent {
heroes = HEROES;
}
创建和注册可注入的服务
ng generate service heroes/hero
生成添加
import { Injectable } from '@angular/core';
import { HEROES } from './mock-heroes';
@Injectable({
// we declare that this service should be created
// by the root application injector.
providedIn: 'root',
})
export class HeroService {
getHeroes() { return HEROES; }
}
注入服务
在hero-list.component 中
import { Component } from '@angular/core';
import { Hero } from './hero';
import { HeroService } from './hero.service';
@Component({
selector: 'app-hero-list',
template: `
<div *ngFor="let hero of heroes">
{{hero.id}} - {{hero.name}}
</div>
`
})
export class HeroListComponent {
heroes: Hero[];
constructor(heroService: HeroService) {
this.heroes = heroService.getHeroes();
}
}
测试带有依赖的组件
test.component.ts
const expectedHeroes = [{name: 'A'}, {name: 'B'}]
const mockService = <HeroService> {getHeroes: () => expectedHeroes }
it('should have heroes when HeroListComponent created', () => {
// Pass the mock to the constructor as the Angular injector would
const component = new HeroListComponent(mockService);
expect(component.heroes.length).toEqual(expectedHeroes.length);
});
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