Angular 4，将可观察到的HTTP响应转换为可观察到的对象 [英] Angular 4, convert http response observable to object observable

问题描述

我对可观察对象的概念是新手，需要一些帮助来进行转换.
我有一个从Http请求返回Observable<Response>的服务，但我需要将其转换为Observable<PriceTag>才能在connect方法内的DataSource上使用它.
反正有这样做吗?

I'm new to the concepts of observables and need some help with a conversion.
I have a service which returns an Observable<Response> from a Http request, but I need to convert it do an Observable<PriceTag> to use it on a DataSource inside the connect method.
Is there anyway to do this?

这是我服务中的方法:

getPriceTags(): Observable<Response> {

    // Set the request headers
    const headers = new Headers({ 'Content-Type': 'application/json' });

    // Returns the request observable
    return this.http.post(Constants.WEBSERVICE_ADDRESS + "/priceTag", null, {headers: headers});

}

这是DataSource类，在这里我需要将其作为Observable<PriceTag>返回:

And here is the DataSource class where I need to return it as an Observable<PriceTag>:

export class PriceTagDataSource extends DataSource<PriceTag> {

    constructor (private priceTagService: PriceTagService) {
        super();
    }

    connect(): Observable<PriceTag> {

        // Here I retrieve the Observable<Response> from my service
        const respObs = this.priceTagService.getPriceTags();

        // Now I need to return a Observable<PriceTag> 

    }

    disconnect() {}

}

以下是我的请求响应中的一个示例:

Here's an example from the response from my request:

{
    // This object is used to check if the query on the server was sucessful
    "query": {
        "sucessful": true
    },

    // These are my PriceTags 
    "tags": [
        {
            "id": "1",
            "name": "MAIN"
        },
        {
            "id": "2",
            "name": "CARD"
        }
    ]
}

推荐答案

从angular 4.3开始，这可以自动完成.

As of angular 4.3 this can be done automatically.

示例:

export class SomeService {
    constructor(private http: HttpClient) {}  // <--- NOTE: HttpClient instead of Http

    getSome(): Observable<MyAwesomeObject> {
        return this.http.get<MyAwesomeObject>('myUrl');
    }
}

因此，您的情况应该是:

So in your case that would be:

return this.http.post<PriceTag>(Constants.WEBSERVICE_ADDRESS + "/priceTag", null, {headers: headers});

同样，使用HttpClient代替Http

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