有可能以某种方式同步调用异步离子存储吗？

Question

我正在尝试创建一个在类顶部使用API​​的Angular2 HTTP类.主要的是我需要添加自定义的auth标头,在用户授权后可用.

主要问题是令牌存储在Ionic Storage模块中,只能异步获取,但我需要返回特定的类型....

export class APIRequest extends Http {

    private storage : Storage;

    constructor (backend: XHRBackend, options: RequestOptions) {
        super(backend, options);

        this.storage = new Storage;
    }

    request(url: string|Request, options?: RequestOptionsArgs): Observable<Response> {
        if (typeof url === 'string') {
            url = AppConfig.API_SERVER + url
        } else {
            url.url = AppConfig.API_SERVER + url.url
        }

        this.storage.get('authToken').then(token => {
            if (typeof url === 'string') {
                if (!options) {
                    options = {headers: new Headers()};
                }

                options.headers.set('Authorization', `Bearer ${token}`);
            } else {
                url.headers.set('Authorization', `Bearer ${token}`);
            }
            // Here I need to return 
        }, err => {
            // throw some error
        })

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

所以基本上我需要以某种方式return super.request(url, options)...兑现存储的承诺并在我获得该令牌时返回.

Answer 1

接近重复.(找不到)

至少,答案可以应用于同一个问题.如果你想保持返回Observable,修复就是将你的Promise(this.storage.get)转换为Observable.

之后,您可以使用运算符flapMap来返回值super.request.

(注意:编译器不明白它Response现在返回一个,所以将返回类型更改为Observable<any>(仍将返回Response))

export class APIRequest extends Http {

    private storage : Storage;

    constructor (backend: XHRBackend, options: RequestOptions) {
        super(backend, options);

        this.storage = new Storage;
    }
    // any return type (will return Response object but compiler doesn't understand that)
    request(url: string|Request, options?: RequestOptionsArgs): Observable<any> {
        if (typeof url === 'string') {
            url = AppConfig.API_SERVER + url
        } else {
            url.url = AppConfig.API_SERVER + url.url
        }

        //convert the Promise to an Observable
        val storageObservable = Observable.fromPromise(this.sotrage.get('authToken'));

        // rxjs/add/operator/mergeMap
        return storageObservable.flatMap(token => {
            if (typeof url === 'string') {
                if (!options) {
                    options = {headers: new Headers()};
                }

                options.headers.set('Authorization', `Bearer ${token}`);
            } else {
                url.headers.set('Authorization', `Bearer ${token}`);
            }
            // the value that will be returned
            return super.request(url, options).catch(this.catchAuthError(this));
        }, err => {
            // throw some error
        })


    }
}

有用的链接:

• 来自reactivex.io的文档.例如,对于flatMap:http: //reactivex.io/documentation/operators/flatmap.html
• 为什么我们需要使用flatMap？