CODEWITHSUNDEEP
javascriptnode.jselectron
Tristan Tran
Tristan Tran

Reputation: 1513

Implementing Promise Reject with dialog.showSaveDialog

I am trying to implement file-saving with dialog.showSaveDialog with the following two approaches:

Approach 1:

const pObj = dialog.showSaveDialog(window, options);
pObj.then(
  onResolved => {
    filename = onResolved.filePath;
    fs.writeFileSync(filename, arg);
  },
  onRejected => {console.log('Promise rejected')}
);

Approach 2:

const pObj = dialog.showSaveDialog(window, options);
pObj.then(
  onResolved => {
    filename = onResolved.filePath;
    fs.writeFileSync(filename, arg);
  }
).catch(err => {
  console.log('No file saved');
});

When I click Cancel instead of Save in the dialog window, Approach 1 throw me an error message, saying that the promise error is uncaught. Approach 2 works fine (i.e., it displays the text No file saved. Why doesn't the pObj in Approach 1 execute the onRejected handler? Doesn't then() method accept two handlers, one for resolved state and one for rejected state? Thanks for explaining.

Upvotes: 0

Views: 180

Answers (1)

Resolver
Resolver

Reputation: 46

The then() method does indeed accept two handlers, one for resolved state and one for rejected state. The reject handler is only called when something goes wrong; however, clicking Cancel instead of Save doesn't trigger an error, it simply returns a different result through the resolve handler.

This is clearly explained in the documentation about dialog.showSaveDialog():

Returns Promise<Object> - Resolve with an object containing the following:

• canceled Boolean - whether or not the dialog was canceled.

• filePath String (optional) - If the dialog is canceled, this will be undefined.

This should work then (untested):

const pObj = dialog.showSaveDialog(window, options);
pObj.then(
  onResolved => {
    if (!onResolved.canceled) {
        filename = onResolved.filePath;
        fs.writeFileSync(filename, arg);
    }
  },
  onRejected => {console.log('Promise rejected')}
);

Upvotes: 3

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