Tips for managing the output of an asynchronous function in TypeScript

Question

Tips for managing the output of an asynchronous function in TypeScript

The casesService function deals with handling an HTTP request and response to return a single object. However, due to its asynchronous nature, it currently returns an empty object (this.caseBook). My goal is for it to only return the object once it has been populated with a value.

public initData(selectedCaseId: number): CaseBook {   

       this.casesService
        .GetCaseById(selectedCaseId)
        .subscribe(data => {

            this.caseBook = data;

        });
       return this.caseBook; 
 }

javascript typescript angular2-services

Answer 1

Answer №1

To utilize Typescript Promises, you can implement it in the following manner:

public async fetchData (selectedItemId: number): Item {       
    return await this.itemService.GetItemById(selectedItemId);
}

However, if your this.itemService.GetItemById function returns an Observable, it might not be feasible to directly return a pure value from it. In that case, return an Observable instead.

public fetchData (selectedItemId: number): Observable<Item> {   
   return this.itemService
    .GetItemById(selectedItemId);
}

Then, you can bind it with Angular 2 using the async pipe:

{{this.fetchData() | async}}

For enhanced performance, it is recommended to bind a value to it. For example:

ngAfterViewInit() {
    this.fetchData().subscribe( data => this.item = data );
}

Answer 2

To utilize Typescript Promises, you can implement it in the following manner:

public async fetchData (selectedItemId: number): Item {       
    return await this.itemService.GetItemById(selectedItemId);
}

However, if your this.itemService.GetItemById function returns an Observable, it might not be feasible to directly return a pure value from it. In that case, return an Observable instead.

public fetchData (selectedItemId: number): Observable<Item> {   
   return this.itemService
    .GetItemById(selectedItemId);
}

Then, you can bind it with Angular 2 using the async pipe:

{{this.fetchData() | async}}

For enhanced performance, it is recommended to bind a value to it. For example:

ngAfterViewInit() {
    this.fetchData().subscribe( data => this.item = data );
}

Tips for managing the output of an asynchronous function in TypeScript

Answer №1

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