从 Promise 内部返回已解决的 Observable [英] Return Resolved Observable from Inside of a Promise

问题描述

我正在尝试通过扩展默认值来构建自定义 Angular 2 http 请求，并且我正在使用 Ionic 2 本地存储来存储身份验证令牌.(将来可能会使用文件系统).我的问题是如何从我的 http 服务返回已解决的承诺，以便我可以订阅组件中的 Observable.我尝试过 Observable.fromPromise 和其他变体均无济于事.

I'm trying to build a custom Angular 2 http request by extending the default and I'm using Ionic 2 local storage to store the auth token. (Will likely use file system in future). My issue is how to return a resolved promise from my http service so I can subscribe to the Observable within my component. I've tried Observable.fromPromise and other variations to no avail.

request(url: string|Request, options?: RequestOptionsArgs): Observable<Response> {

  // Get the token used for this request.
  // * Need to return this promise resolved.
  var promise = this.storage.get('token').then(token => {

    if (typeof url === 'string') { // meaning we have to add the token to the options, not in url
      if (!options) {
        // let's make option object
        options = {headers: new Headers()};
      }
      options.headers.set('Authorization', 'Basic ' + token);
    } else {
    // we have to add the token to the url object
      url.headers.set('Authorization', 'Basic ' + token);
    }

    return super.request(url, options).catch(this.catchAuthError(this));

  }).catch(error => {
    console.log(error);
  });

}

想法基于这篇博文，但离子存储返回了一个承诺.http://www.adonespitogo.com/articles/angular-2-扩展-http-provider/

Idea is based on this blog post, but Ionic storage returns a promise. http://www.adonespitogo.com/articles/angular-2-extending-http-provider/

推荐答案

我不知道该存储是否返回与 Rx 兼容的 Promise，但如果是，那么解决方案应该如下所示:

I don't know if that storage returns a promise which is compatible with Rx, but if it is then the solution should look like this:

request(url: string|Request, options?: RequestOptionsArgs): Observable<Response> {

    return Observable
        .fromPromise(this.storage.get('token'))
        .flatMap(token => {

            if (typeof url === 'string') { // meaning we have to add the token to the options, not in url
                if (!options) {
                    // let's make option object
                    options = {headers: new Headers()};
                }
                options.headers.set('Authorization', 'Basic ' + token);
            } else {
                // we have to add the token to the url object
                url.headers.set('Authorization', 'Basic ' + token);
            }

            return super.request(url, options).catch(this.catchAuthError(this));

        });
    });

}

如果 promise 与 observables 不兼容，仍然有办法做到这一点，尽管它不是那么优雅:

If promise is not compatible with observables there's still a way to do that, though it's not that elegant:

request(url: string|Request, options?: RequestOptionsArgs): Observable<Response> {

    return Observable.create((observer: Observer) => {

        this.storage.get('token').then(token => {

            if (typeof url === 'string') { // meaning we have to add the token to the options, not in url
                if (!options) {
                    // let's make option object
                    options = {headers: new Headers()};
                }
                options.headers.set('Authorization', 'Basic ' + token);
            } else {
                // we have to add the token to the url object
                url.headers.set('Authorization', 'Basic ' + token);
            }

            super.request(url, options).catch(this.catchAuthError(this)).subscribe(result => {
                observer.next(result);
                observer.complete();
            });

        }).catch(error => {
            observer.error(error);
        });

    });

}

这篇关于从 Promise 内部返回已解决的 Observable的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！