CODEWITHSUNDEEP
angularobservableobserver-patternsubscribe
Guy E
Guy E

Reputation: 1927

get observable from a subscription

After doing some experiments, I post the code without my changes, to find the best practice: I have a function (in service) that subscribes to a result as a BLOB and save it as a content of a file to the local file system - FileSaver.saveAs(result, );:

printAsPDF()
{
   if (<some validator fails>)
   {
      return;
   } 
   let htmlContent = "<html><body>" + <some html content> +"</body></html>";
   //this.GetByteArrayForPDF returns Observable<any> (actually observable of a blob)
   this.GetByteArrayForPDF(htmlContent).subscribe(result => 
   {
      FileSaver.saveAs(result, <file name>); 
   }, error => console.log(error));
}

Now, I want that function printAsPDF to return also an observable which indicate whether the save action succeeded or not. Currently, the call to that function is being executed from a component: 

this.<service name>.printAsPDF();

I want that component function to subscribe to the observable and check if the saving succeeded or not. How can I do it taking into consideration that the call to printAsPDF should get an observable(true) depending if FileSaver.saveAs(result, ) was called

Upvotes: 2

Views: 445

Answers (1)

BradleyDotNET
BradleyDotNET

Reputation: 61369

Change your subscribe to a map (you'll need to subscribe in your component to make the observable hot of course). You can move the error handler to your component or put it in a catch method. 

return this.GetByteArrayForPDF(htmlContent)
.map(result => 
{
   FileSaver.saveAs(result, <file name>); 
   return true;
})
.catch(error => { 
    console.log(error);
    return Observable.of(false);
});

or using pipeable operators (RxJS 5.5+):

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

return this.GetByteArrayForPDF(htmlContent).pipe(
map(result => 
{
   FileSaver.saveAs(result, <file name>); 
   return true;
}),
catchError(error => { 
    console.log(error);
    return Observable.of(false);
}));

Upvotes: 1

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