问题
The casesService function handles a HTTP req and response and returns a single object. I want to return the object. But since it is an async functionality it returns empty object(this.caseBook). I want it to return the object only after it has value.
public initData (selectedCaseId: number): CaseBook {
this.casesService
.GetCaseById(selectedCaseId)
.subscribe(data => {
this.caseBook = data;
});
return this.caseBook;
}
回答1:
For typescript Promise, you can make it work this way:
public async initData (selectedCaseId: number): CaseBook {
return await this.casesService.GetCaseById(selectedCaseId);
}
but since your this.casesService.GetCaseById is an Observable, you may not possible to return pure value from it directly. return an Observable instead.
public initData (selectedCaseId: number): Observable<CaseBook> {
return this.casesService
.GetCaseById(selectedCaseId);
}
and then you can bind it for angular2 with async pipe:
{{this.initData() | async}}
for better performance, suggest to bind a value for it, for example:
ngAfterViewInit() {
this.initData().subscribe( data => this.caseBook = data );
}
来源：https://stackoverflow.com/questions/45413433/how-to-handle-the-return-value-of-async-function-in-typescript