How can i wait for the response of the subcribe

Question

Is there a way to wait the response of my Observer before i return the value?

data(): MatTableDataSource<ITableData> {
        var datasource: MatTableDataSource<ITableData> = new MatTableDataSource()

        var ob: Observer<any> = {
            next: (result: any) => {
                const l = this.processData(result)
                datasource = new MatTableDataSource(l)
            },

            error: (err: Error) => {
                console.log(err)
            },

            complete: () => {
            }
        }


        this.getDataFromJson().subscribe(ob);
        console.log(datasource)
        return datasource;
    }

Right now it doesn't return the value attributed in the observer but the new MatTableDataSource() from when i declare it. Because the return executes before my Observer.

Expected Result: datasource.data = Array(15) Result got: datasource.data = Array(0)

You should elaborate more on what *doesn't return the correct values* actually means. — Octavian Mărculescu, Sep 12 '22 at 09:15
Maybe you want to use something like `pipe(...)` before your `.subscribe` but its hard to tell. I agreed that you should elaborate more your question and expected results. — cybering, Sep 12 '22 at 09:22
You can see this question - https://stackoverflow.com/questions/57770423/how-to-use-the-mattabledatasource-with-an-observable — Alimur Razi Rana, Sep 12 '22 at 09:30

Octavian Mărculescu · Accepted Answer · 2022-09-12T11:29:55.647

Another way to do this is to declare your data source as a property on the component (or any other class that holds this logic) and only instantiate it once:

public datasource = new MatTableDataSource<ITableData>();

public loadData(): void {
  this.getDataFromJson().subscribe((result: any) => {
    this.datasource.data = this.processData(result);
  });
}

You can now call loadData whenever you need to refresh the data and your datasource will reflect the new changes.

How can i wait for the response of the subcribe

1 Answers1