Observable mit switchMap Typ Fehler

Question

Ich lerne immer noch RxJS und ich versuche, eine Datentabelle einzurichten, die einen Datenstrom beobachtet, der sich über einen Dienst ändert, kann jemand meinen Code ansehen und mir sagen, wie man das bekommt richtige Antwort von diesem Observablen?

search.service.ts

@Injectable() 
export class SearchService { 
    constructor(
     private apiService: ApiService 
    ) { } 

    private searchSource = new BehaviorSubject<object>(this.getInitialCollections()); 

    public currentMessage = this.searchSource.asObservable(); 

    getInitialCollections(): object { 
     return this.apiService.get('/cmt-api/search/merch/collections/_search'); 
    } 

    search(phrase: string) { 
     let results = this.apiService.post('/cmt-api/search/merch/collections/_search', { phrase: phrase }) 
      .subscribe(data => this.changeMessage(data)); 
    } 

    changeMessage(results: object) { 
     this.searchSource.next(results) 
    } 

    readCollectionResult(result: any): Asset[] { 
     let data = JSON.parse(result._body).data; 
     return data.map(asset => { 
      return { 
       id: asset.id, 
       collectionName: asset.collectionName, 
       collectionId: asset.collectionId, 
       objectType: asset.objectType, 
       displayType: asset.displayType, 
       size: asset.size, 
       createDate: asset.createDate, 
       modifiedDate: asset.modifiedDate, 
       publishedDate: asset.publishedDate, 
       parentFolderId: asset.parentFolderId 
      }; 
     }); 
    } 
} 

datatable.component.ts

@Component({ 
    selector: 'mat-datatable', 
    styleUrls: ['./datatable.component.scss'], 
    templateUrl: './datatable.component.html', 
}) 
export class DatatableComponent { 
    displayedColumns = ['id', 'collectionName', 'displayType', 'size']; 
    datatableDatabase: SearchDataSet | null; 
    dataSource: SearchDataSource | null; 

    constructor(
     private searchService: SearchService 
    ) { 
     this.datatableDatabase = new SearchDataSet(searchService); 
     this.dataSource = new SearchDataSource(this.datatableDatabase); 
    } 
} 

export class SearchDataSet { 
    dataChange: BehaviorSubject<Asset[]> = new BehaviorSubject<Asset[]>([]); 
    get data(): object { return this.dataChange.value; } 

    constructor(
     private searchService: SearchService 
    ) { } 

    getCollections() { 
     this.searchService.currentMessage.subscribe(results => { 
      this.dataChange.next(this.searchService.readCollectionResult(results)) 
     }); 
    } 
} 

export class SearchDataSource extends DataSource<Asset> { 
    constructor(private _searchDataset: SearchDataSet) { 
     super(); 
    } 

    /** Connect function called by the table to retrieve one stream containing the data to render. */ 
    connect(): Observable<Asset[]> { 
     return this._searchDataset.dataChange 
      .switchMap(() => { <----- ERROR (see below) 
       return this._searchDataset.getCollections() 
      }); 
    } 

    disconnect() { } 
} 

Fehler:

Argument of type '() => void' is not assignable to parameter of type '(value: Asset[], index: number) => ObservableInput<Asset[]>'. 

Answer 1

dies versuchen. getCollections müssen ein Observable zurückgeben

getCollections() { 
    return this.searchService.currentMessage.map(results => { 
     return this.searchService.readCollectionResult(results) 
    }).map(value=>{ 
     this.dataChange.next(value) 
     return value 
    }); 
}