如何从有前景的函数中返回可观察到的

Question

I have a function with a promise in it. I would like the function to return observable when the promise occur. See my code:

  public exportAsExcel() : Observable<void>
  {
    let workbook = new Workbook();
    .....
    ......
    workbook.xlsx.writeBuffer().then((data) => 
    {
        this.doSomething(data);
        return of();
    });

  }    

Answer 1

Use from , which turns your promise to an observable:

import { from } from 'rxjs';
import { map } from 'rxjs/operators';

// ...

return from(workbook.xlsx.writeBuffer()).pipe(
 map(...)
)

Answer 2

return new Observable(obs=>{

       let workbook = new Workbook();
        .....
       ......
       workbook.xlsx.writeBuffer().then((data) => 
       {
          this.doSomething(data);
          return obs.next(data);
        });
    })

Or using rxjs from and map

return from(workbook.xlsx.writeBuffer()).pipe(map(data => {
   // process something
   return dataTransformed
}))