<any> 在 Typescript class 构造函数参数前面是什么意思？

Question

我正在阅读 Angular - Testing 文档。在描述如何测试异步 services（测试 HTTP 服务）时，我遇到了一个 class 构造函数，在传递的参数前面有一个 <any>。完整的行由

给出

heroService = new HeroService(<any> httpClientSpy);

我知道，Typescript 中的 any 代表字面上的 "any" 类型。 guillemets (<...>) 有什么用？为什么在参数前面打字？是否用于类型解析？

文档中的完整代码：

let httpClientSpy: { get: jasmine.Spy };
let heroService: HeroService;

beforeEach(() => {
  // TODO: spy on other methods too
  httpClientSpy = jasmine.createSpyObj('HttpClient', ['get']);
  heroService = new HeroService(<any> httpClientSpy);
});

it('should return expected heroes (HttpClient called once)', () => {
  const expectedHeroes: Hero[] =
    [{ id: 1, name: 'A' }, { id: 2, name: 'B' }];

  httpClientSpy.get.and.returnValue(asyncData(expectedHeroes));

  heroService.getHeroes().subscribe(
    heroes => expect(heroes).toEqual(expectedHeroes, 'expected heroes'),
    fail
  );
  expect(httpClientSpy.get.calls.count()).toBe(1, 'one call');
});

it('should return an error when the server returns a 404', () => {
  const errorResponse = new HttpErrorResponse({
    error: 'test 404 error',
    status: 404, statusText: 'Not Found'
  });

  httpClientSpy.get.and.returnValue(asyncError(errorResponse));

  heroService.getHeroes().subscribe(
    heroes => fail('expected an error, not heroes'),
    error  => expect(error.message).toContain('test 404 error')
  );
});

Answer 1

这是类型断言。

Originally the syntax that was added was <foo>. However, there is an ambiguity in the language grammar when using <foo> style assertions in JSX. Therefore it is now recommended that you just use as foo for consistency.

https://basarat.gitbooks.io/typescript/docs/types/type-assertion.html

Answer 2

HeroService 正在被实例化为 SpyObject

遵循结构 |Object

茉莉花可以打卡documentation

<any> 在 Typescript class 构造函数参数前面是什么意思？

What does <any> mean infront of an Typescript class constructor argument?

typing

typescript

angular