Getting [Object Object] in angular2 application

问题

I have developed angular2 application using ngrx/effects for making http calls. I have used GIT as reference application. Once the response come from http, i am not able to display it on screen. Its showing [object Object]. Here is my code.

HTML page linked to component.html

<div class="container">
<div class="left-container cf">
<mat-tab-group>
    <mat-tab label="Configuration">{{jsons}}</mat-tab>
    <mat-tab label="Captured Output">
    </mat-tab>
</mat-tab-group>
</div>
</div>

Component.ts

        export class ExperimentDetailsComponent implements OnInit {

      jsons: Observable<any>;
      isLoading: Observable<any>;

      constructor(
        private store: Store<fromStore.State>
      ) {
        this.isLoading = store.select(fromStore.getIsLoading);
        this.jsons = store.select(fromStore.getJson);
        console.log(this.jsons)
      }

      ngOnInit() {
        this.store.dispatch(new jsonAction.GetJson());
        // this.jsons = this.store.select(fromStore.getJson);
      }
    }

Effects.ts

        export class GetJsonEffects {

      @Effect() json$ = this.actions$.ofType(Act.GET_JSON)
        .map(toPayload)
        .withLatestFrom(this.store$)
        .mergeMap(([ payload, store ]) => {

          return this.http$
            .get(`http://localhost:4000/data/`)
            .map(data => {
              return new Act.GetJsonSuccess({ data: data })
            })
            .catch((error) => {
              return Observable.of(
                new Act.GetJsonFailed({ error: error })
              );
            })
        });


      constructor(
        private actions$: Actions,
        private http$: HttpClient,
        private store$: Store<fromStore.State>
      ) {}
    }

回答1:

As you see, the result of store.select() is an observable. You cannot data bind to it directly.

You can either:

Use the async pipe to make the UI subscribe to the observable for you and extract the data, like:

<mat-tab label="Configuration">{{jsons | async}}</mat-tab>

Or subscribe yourself to the observable.

export class ExperimentDetailsComponent implements OnInit {

     jsonSubscription = store.select(fromStore.getJson)
          .subscribe(jsons => this.jsons = jsons);

    ngOnDestroy() {
      this.jsonSubscription.unsubscribe();
    }
      jsons: any;

     // ...
}

That's one thing:

If you are using Http service (from @angular/http module):

The other thing is that you are returning the Response object not the JSON extracted from it. The map() in your effect needs to call data.json(). Like:

      return this.http$
        .get(`http://localhost:4000/data/`)
        .map(data => {
          return new Act.GetJsonSuccess({ data: data.json() })
        })

Or, as I like, add another map() to make things clear:

      return this.http$
        .get(`http://localhost:4000/data/`)
        // You could also create an interface and do:
        //   `response.json() as MyInterfaceName` 
        //   to get intellisense, error checking, etc
        .map(response => response.json())
        .map(data => {
          return new Act.GetJsonSuccess({ data: data })
        })

If you are using HttpClient service (from @angular/common/http module):
(Available in Angular v4.3+)

In this case you don't need to call .json() yourself, it does it for you, so you don't need that first .map() I suggested.

You can also tell TypeScript about the type you expect the JSON to match by calling the get() like this:

      return this.http$
        .get<MyInterfaceName>(`http://localhost:4000/data/`)
        .map(data => {
          return new Act.GetJsonSuccess({ data: data.json() })
        })

The get<MyInterfaceName>() bit will make Angular tell TypeScript that the JSON object matches the MyInterfaceName, so you'll get intellisense and error checking based on this (at compile time only, none of this affects runtime in anyway).

HttpClient Documentation

来源：https://stackoverflow.com/questions/47153196/getting-object-object-in-angular2-application