Angular抽象类HttpClient注入 [英] Angular abstract class HttpClient injection

问题描述

大家好，我是Angular的新手，但我在Injectable类方面遇到了麻烦.

Hi everyone, i'm new with Angular and I am having troubles with Injectable classes.

我有一个抽象类(在web.ts上)，该类的受保护属性之一是HttpClient对象.该抽象类的定义如下:

I have an abstract class (on web.ts) which one of its protected attributes is an HttpClient object. The definition of this abstract class is as follows:

import { HttpClient } from "@angular/common/http";


export abstract class Web {
   protected baseURL: string;

   constructor(baseURL: string, protected http: HttpClient) {
      this.baseURL =  baseURL;
   }

   public abstract RetrieveData(pattern: string);
}

然后，我有另一个类(在webA.ts上)扩展了Web类:

Then I have another class (on webA.ts) which extends the Web class:

import { Web } from './web';

export class WebA extends Web {

   constructor() {
      super("https://www.test.com");
   }

   private Search(pattern: string) {
      pattern = pattern.replace(" ", "+");
      var searchURL = this.baseURL + `/site/searchpage.jsp?st=${pattern}&id=pcat17071`;

      console.log(searchURL);

      this.http.get(searchURL).subscribe(data => {
         console.log(data);
      });
   }

   public RetrieveData(pattern: string) {
      this.Search(pattern);
   }
}

最后，在我的网站的组件类中，我想将WebA实例化为:

Finally, in a class of a component for my website I want to instantiate WebA as:

private webA: Web = new WebA();

它告诉我，我需要在webA.ts中的super("https://www.test.com");上传递HttpClient对象.要解决此问题，我可以使WebA的构造函数如下:

It tells me that I need to pass an HttpClient object on super("https://www.test.com"); in webA.ts. To fix it, I can make the constructor for WebA like:

constructor(@Inject(HttpClient) http: HttpClient) {
      super("https://www.test.com", http);
}

但这会导致我执行private webA: Web = new WebA(this.http);强制我进入组件类:

But this would lead me to do private webA: Web = new WebA(this.http); forcing me to have on my component class:

import { HttpClient } from "@angular/common/http";
...
constructor(private http: HttpClient) {}

我知道必须有另一种方法，因为我认为这破坏了我班级的层次结构

I know there must be another way to do it because in my opinion this is breaking hierarchy on my classes

TL; DR:
我需要在抽象类上自动注入" HttpClient，而不需要将此对象作为扩展程序类中super的参数传递.

TL;DR:
I need to "auto-inject" an HttpClient on an abstract class to not to need passing this object as an argument on super in the extender class.

推荐答案

要么删除WebA

export class WebA extends Web {

   //constructor() {
   //   super("https://www.test.com");
   //}

或重复构造函数参数，并使用super()

or repeat the constructor parameters and forward them with super()

export class WebA extends Web {

   constructor(baseURL: string, protected http: HttpClient) {
      super(baseURL, http);
   }

如果在派生类(WebA)中需要构造函数，则唯一的方法是重复并转发参数.

If you need a constructor in the derived class (WebA) the only way is to repeat the parameters and forward them.

更新

使用new Xxx()创建实例时，没有自动注入之类的功能.依赖注入仅适用于Angulars DI为您创建的实例.

There is no such thin as auto-inject when you create an instance with new Xxx(). Dependency injection works only for instances that Angulars DI creates for you.

否则，请参见上面的答案.

Otherwise see my answer above.

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