Angular (5) httpclient 观察和响应类型:'blob' [英] Angular (5) httpclient observe and responseType: 'blob'

问题描述

上下文:我正在尝试从后端下载一个二进制文件(这需要一些作为 json-body 发布的数据)，并使用后端在 content-disposition 标头中指定的文件名将其保存在文件保护程序中.要访问标头，我认为我需要 HttpResponse.

Context: I'm trying to download a binary file from a backend (that requires some data posted as json-body) and save it with file-saver using the filename specified by the backend in the content-disposition header. To access the headers I think I need the HttpResponse.

但我无法将 angular 的 HttpClient.post(...): Observable>; 方法与 Blob 一起使用.

But I'm unable to use angular's HttpClient.post<T>(...): Observable<HttpResponse<T>>; method with a Blob.

当我打电话

this.httpclient.post<Blob>('MyBackendUrl', 
        params, 
        {observe: 'response', responseType: 'blob'});
the compiler complains about the 'blob' ('json' is accepted by the compiler):


error TS2345: Argument of type '{ observe: "response"; responseType: "blob"; }' is not assignable to parameter of type '{ headers?: HttpHeaders | { [header: string]: string | string[]; }; observe?: "body"; params?: Ht...'.
  Types of property 'observe' are incompatible.
    Type '"response"' is not assignable to type '"body"'.

当我将选项放入自己的对象中时，如 https://stackoverflow.com/a/48016652/2131459(但没有as"...) post(...):Observable 被调用，我无法访问标题.

When I put the options in an own object as seen in https://stackoverflow.com/a/48016652/2131459 (but without the "as" ...) the post(...):Observable is called and I cannot access the headers.

顺便说一句，即使是简单的例子 return this.http.get('backendUrl', {responseType: 'blob'}); 如所见，例如在 https://stackoverflow.com/a/46882407/2131459 中对我不起作用.

Btw, even the simple example return this.http.get<Blob>('backendUrl', {responseType: 'blob'}); as seen e.g. in https://stackoverflow.com/a/46882407/2131459 doesn't work for me.

使用的版本

• Angular 版本:5.0.3(将在一周左右更新到最新的 5 个)
• 打字稿:2.4.2
• webpack:3.8.1

推荐答案

使用 observe:response 时，不要输入调用 (post(...))，因为返回的 Observable 将是 HttpResponse.所以这应该有效:

When using observe:response, don't type the call (post<Blob>(...)), as the returned Observable will be of HttpResponse. So this should work:

this.httpclient.post('MyBackendUrl', 
    params,
    {observe: 'response', responseType: 'blob'}
);

为什么会发生这种情况，是否有两种版本的 post 方法，一种具有泛型类型，一种没有:

Why this happens, is there's two versions of the post method, one with a generic type, one without:

/**
     * Construct a POST request which interprets the body as JSON and returns the full event stream.
     *
     * @return an `Observable` of all `HttpEvent`s for the request, with a body type of `T`.
     */
    post<T>(url: string, body: any | null, options: {
        headers?: HttpHeaders | {
            [header: string]: string | string[];
        };
        observe: 'events';
        params?: HttpParams | {
            [param: string]: string | string[];
        };
        reportProgress?: boolean;
        responseType?: 'json';
        withCredentials?: boolean;
    }): Observable<HttpEvent<T>>;
    /**
     * Construct a POST request which interprets the body as an `ArrayBuffer` and returns the full response.
     *
     * @return an `Observable` of the `HttpResponse` for the request, with a body type of `ArrayBuffer`.
     */
    post(url: string, body: any | null, options: {
        headers?: HttpHeaders | {
            [header: string]: string | string[];
        };
        observe: 'response';
        params?: HttpParams | {
            [param: string]: string | string[];
        };
        reportProgress?: boolean;
        responseType: 'arraybuffer';
        withCredentials?: boolean;
    }): Observable<HttpResponse<ArrayBuffer>>;

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