为什么 Angular 没有为 HttpClient.get(...) 选择正确的重载? [英] Why is Angular not choosing correct overload for HttpClient.get(...)?

问题描述

我正在尝试将一些 HttpClient 调用(.get(...) 和 .post(...))抽象到一个 BaseService 类中，因为如果我的服务，我必须复制标头和凭据等代码不要从基类继承.

I'm trying to abstract out some HttpClient calls (.get(...) and .post(...)) into a BaseService class since I'm having to duplicate code such as headers and credentials if my services don't inherit from a base class.

这样做时，出于某种原因，我的代码没有选择 get 上的通用重载.

In doing this, for some reason my code isn't choosing the generic overload on the get.

以下方法调用成功选择了正确的 HttpClient.get(...) 重载:

The following method call is successfully choosing the correct HttpClient.get(...) overload:

但是，以下是选择不同的重载，我不知道如何解决它:

However, the following is choosing a different overload, and I have no idea how to fix it:

这是因为我错误地声明了私有选项字段吗?我在 API 文档中找不到更好/正确的声明方式，以便成功选择正确的重载.有人可以帮我让我的代码为 HttpClient.get(...) 选择正确的(通用 Observable)重载吗?

Is this because I'm declaring the private options field incorrectly? I can't find in the API docs a better/correct way of declaring it so that the correct overload will be chosen successfully. Can someone please help me make my code choose the correct (generic Observable<T>) overload for HttpClient.get(...)?

推荐答案

这是因为您要声明类型为 any 的选项.

This is because you are declaring options with type any.

通过这样做，编译器一无所知options 的接口/成员，尽管您使用由 2 个属性组成的对象实例化其值.

By doing this, the compiler knows nothing about the interface/members of options, despite the fact that you instantiate its value with an object made of 2 properties.

重构为:

export class Foo {
   private options = {headers: {...}, withCredentials: true};
   ....
}

现在编译器可以推断options的类型，而不是静态读取它.

Now the compiler can infer the type of options, instead of statically reading it.

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