[FEATURE ember-metal-meta-destructors]

[rwjblue]

Introduces a mechanism to add additional work to be done at object / meta destruction time.

Example:

// app/utils/run-later.js
export default function runLater(object, functionOrName, delay) {
  let cancelId = run.later(object, functionOrName, delay);
  Ember.meta(object).addDestructor(() => run.cancel(cancelId));
}

// some component
export default Component.extend({
  stuff() { },

  actions: {
    doStuff() {
      runLater(this, this._stuff, 1000);
    }
  }
})

When this component is destroyed, the scheduled task will be canceled. A number of popular addons do similar things by monkey patching the objects willDestroy at runtime, but that is less than ideal (due to shape changes and whatnot).

This provides a mechanism to easily entangle cleanup tasks for objects from utility functions...

[rwjblue]

Would love review/feedback from folks I know have been working on and around similar issues to my example above.

/cc @machty @krisselden @stefanpenner @runspired

[machty]

Alternatively, wouldn't it be possible to implement destructors using ember-metal's listener APIs and just broadcast a willDestroy event? Then anyone will be able to do Ember.on('willDestroy', ()=>{}) and have all the destructors determined up front at mixin time. Not to mention people would expect there to be willDestroy events if there's an init event.

[runspired]

I think we should go all in on cancellation tokens as the primitive for these things, and I'm hesitant to grow the API surface area instead of doubling down on building a great async story top to bottom.

But otherwise, looks good, seems forward compatible.

[pixelhandler]

@rwjblue I like the idea of cancelling a scheduled task during the destroy phase. Over the past week I've had to add checks for this.isDestroying and this.isDestroyed in scheduled functions for components. During testing components are torn down much quicker and more often compared to using an app. So, with your suggestion here, the extra guarding could go away - nice.

[homu]

☔ The latest upstream changes (presumably #14360) made this pull request unmergeable. Please resolve the merge conflicts.

[locks]

Not applicable anymore.

[rwjblue]

For those that might stumble across this old PR, this was RFC'ed in emberjs/rfcs#545