Odtnhj

What is wrong with the syntax here mergeMap(names => names),?

getIds(): void 
this.myservice
.getIds.pipe( mergeMap(id => this.getNames(id)), 
mergeMap(names => names), toArray() ) 
 

myservce.ts has the following:

getIds():Observable<Ids>
const url = 'http://localhost:4000';
return this.http
 .post(url, '')
 .map(( Ids : any) => Ids.map(item => (Id: item.Id, 
 Name: item.Name ))) as Observable<Ids>;


getNames(data: Ids):Observable<any> 
 const url ='http://localhost:5000';
 return this.http
 .post(url,data)
 .pipe(map(( Results : any) => Results[0].results.map(item => (Id: item.ID, Name: item.Name ))));
 

The compiler error is (as a newbie I'm not able to figure out):

ERROR in src/app/cvetable/mcomponent.ts(132,19): error TS2345:
Argument of type '(names: ) => ' is not assignable to parameter 
of type '(value: , index: number) => ObservableInput<any>'. 
Type '' is not assignable to type 'ObservableInput<any>'. 
Type '' is not assignable to type 'Iterable<any>'. 
Property '[Symbol.iterator]' is missing in type ''.

There's something seriously wrong with the getIds method in your Service:

Here's how it should be. Since you're using HttpClient and your eg is in Angular 7 which uses Rxjs 6+, you'll have to chain a .pipe call to your Observable value in order to apply operators on it. Inside the .pipe call, you can then place a list of comma separated operators:

getIds(obj):Observable<Ids>
 return this.http
 .post(this.url, obj)
 .pipe(
 map((Ids: any) => Ids.map(item => (Id: item.Id, Name: item.Name ) ) )
 )

Here's an Updated StackBlitz with the errors fixed.

You should use switchMap instead of mergeMap

getIds(): void 
 this.myservice
 .getIds.pipe(switchMap(id => this.getNames(id)))