Using triggerPromise I only receive one argument in .then?

[spoike]

Reported by @ponelat in reflux/refluxjs#416

When I have a triggerPromise... I only receive the first argument in then clause.

var someAction = Reflux.createAction({asyncResult: true});
someAction.listen(function(a,b,c) {
  someAction.completed(a + '-eh', b + '-eh', c + '-eh')
})

someAction.triggerPromise(a,b,c)
  .then(function(d,e,f) { // Assume d,e,f are passed into 
    console.log(d,e,f) // <- Only d is defined
  })
.catch(function() {})

I've looked into the source and I'm not sure why this is assumed to be an array of args?... https://github.com/reflux/reflux-core/blob/master/src/PublisherMethods.js#L159

Could be a bug, or it might be me. I can PR if I get some time, but otherwise help is always appreciated!

[levrik]

This isn't possible due to limitations of the Promise API. It only allows one argument in the callbacks.
(Source: http://stackoverflow.com/a/22776850/3443442)

It tried this

var removeSuccess = me.completed.listen(function () {
    removeSuccess();
    removeFailed();
    resolve.apply(null, arguments);
});

but only the first argument is defined in the then-callback.

[spoike]

Actually I believe you can by using arrays and Promise.all to handle the arguments internally. This leads to the following changes:

• (Breaking) then will have array as first argument

In order to have the user use the array as arguments they can do either the following:

• The user needs to use spread method instead to have the array spread out to arguments, which is supported by most Promise implementation

someAction.triggerPromise(a, b, c)
  .spread((d, e, f) => {
    console.log(d, e, f);

  })

• Destructure the array

someAction.triggerPromise(a, b, c)
  .then(() => {
    var { d, e, f } = arguments;
    console.log(d, e, f);
  })

[levrik]

I will try this later

[ponelat]

@spoike @DerNivel thanks for the follow up to this issue!

[levrik]

@spoike spread is not available in the native implementation of Promise. But with this change down below we could support Promise libraries that support it:

var removeSuccess = me.completed.listen(function () {
    var args = Array.prototype.slice.call(arguments);
    removeSuccess();
    removeFailed();
    resolve(args.length > 1 ? args : args[0]);
});

In ES6 this would be possible with the native implementation of Promise:

someAction.triggerAsync().then(([obj1, obj2]) => {
    // obj1 and obj2 are available
});

If this is okay I'll create a PR.

[spoike]

@DerNivel 👌

[levrik]

#7 fixes this issue

[spoike]

Other than #7, we also need to:

• Add to the README a note on the use of arrays
• Add a proper test, so this won't regress