[英]Aurelia dependency injection when instantiating objects
如果我創建一個支持類,例如將HttpClient注入其中的UserList,那么實例化該類的任何人都必須在構造函數中將HttpClient對象傳遞給它。 不應該@inject(HttpClient)負責獲取HttpClient單例並將其注入構造函數中嗎? 否則,每個需要引用UserList的類也將獲得對HttpClient的引用,以便它可以將其傳遞給UserList構造函數(並且無法實現注入的目的)。
UserList.ts
@inject(HttpClient)
export class UserList {
constructor(public http: HttpClient){
}
...
}
DoSomething.ts
export class DoSomething {
userList: UserList;
constructor(){
this.userList = new UserList(); //doesn't work without passing HttpClient
}
}
為了完成這項工作,我必須在DoSomething類中獲得對HttpClient的引用,即使它不會直接使用它。 似乎執行不力的工作版本:
DoSomething.ts
@inject(HttpClient)
export class DoSomething {
userList: UserList;
constructor(public http: HttpClient){
this.userList = new UserList(http);
}
}
如果你使用打字稿,不要擔心這個。 使用@autoinject看看魔法發生了!
像這樣:
import {autoinject} from 'aurelia-framework';
@autoinject()
export class UserList {
constructor(private http: HttpClient){
}
...
}
在其他文件中:
import {autoinject} from 'aurelia-framework';
@autoinject()
export class DoSomething {
constructor(private userList: UserList){
}
}
TypeScript編譯器將發出類型元數據,Aurelia將以正確的方式讀取此注入實例!
有關以下內容的更多信息: http : //aurelia.io/docs.html#/aurelia/dependency-injection/1.0.0-beta.1.2.3/doc/article/dependency-injection-basics
處理此問題的正確方法是使用Factory
Resolver
import { Factory } from 'aurelia-framework';
@inject(Factory.of(UserList))
export class DoSomething {
userList: UserList;
constructor(UserList) {
// this is a factory, so you call the function without new
this.userList = UserList();
}
}
@inject(HttpClient)
export class UserList {
http: HttpClient;
constructor(HttpClient) {
this.http = HttpClient;
}
}
您需要在DoSomething中注入UserList
import {UserList} from 'where-ever-user-list-is';
import {inject} from 'aurelia-framework';
@inject(UserList)
export class DoSomething {
userList: UserList;
constructor(userList){
this.userList = userList
}
}
如果要使用Aurelia dependency injection
,則需要導入所需的模塊:
import {HttpClient} from 'aurelia-fetch-client';
import {inject} from 'aurelia-framework';
@inject(HttpClient)
export class DoSomething{
constructor(http){
// do your stuff
}
}
這是我使用的ES6實現,但我相信你需要改變的只是constructor
的type
。
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