我有多个组件需要相同的依赖项,这需要构造函数的字符串.如何告诉angular2使用DI的特定类型实例？
例如：
ChatUsers.ts：
@Component({
selector: "chat-users"
})
@View({
directives: [],templateUrl: '/js/components/ChatUsers.html'
})
export class ChatUsers {
constructor(public currentUser : User) {
}
}
和app.ts：
/// <reference path="../libs/typings/tsd.d.ts" />
import {Component,View,bootstrap} from 'angular2/angular2';
import {User} from "User";
// How to create a user,e.g. new User('John') and use it for DI?
@Component({
selector: 'chat-app'
})
@View({
directives: [ ],template: `
<div> Some text
</div>`
})
class ChatApp {
constructor(public user: User) {
// do something with user
}
}
bootstrap(ChatApp,[ User ]);
User.ts
export class User {
name: string;
constructor(name: string) {
this.name = name;
}
}
Cannot resolve all parameters for User(?). Make sure they all have
valid type or annotations.
我正在使用最新的angular2版本：2.0.0-alpha.44
解决方法
要使依赖项可选,只需使用
@Optional参数装饰器(参见
this plunker)：
class User {
name: string;
constructor(@Optional() name: string) {
this.name = name;
}
}
>向应用提供商添加一些’userName’提供商,并使用@Inject('userName')参数装饰器将其注入用户(参见this plunker).
class User {
name: string;
constructor(@Inject('userName') name: string) {
this.name = name;
}
}
// ...
bootstrap(ChatApp,[
User,provide('userName',{ useValue: 'Bob'})
]);
>使用useFactory专门实例化您的用户(参见this plunker)：
bootstrap(ChatApp,[
provide(User,{ useFactory: () => new User('John') })
]);
