awesometalk-feedback.md

Ember.select Slide

• s/Ember.select/Ember.Select i think.

This slide is damn funny ^_^

Array Computed Slide

Nothing to add to the slide, but a minor note to keep in mind: there is another difference. arrayComputed adds observers to keep refs up to date. So eg

var array = obj.get('someArrayComputedProperty');

// later modify dependency
// array is kept up to date

It would be nice to not have to do this: would like to make the reduceComputed stuff support lazy, but it's not there yet.

More Things to Mention / Keep in Mind

• callbacks get given changeMeta with many useful properties, like index of item that changed

• callbacks also given instanceMeta, a scratchpad that is 〈instance, property〉 specific where you can keep track of things for more involved properties. For example, intersect keeps track of a count of items seen per dependent array to know when an item belongs in the intersection and when it does not.

• It is possible to depend on properties of items in arrays. This will still give callbacks the right index. This is actually non-trivial when you think about it (it's also not as performant as doing non-property stuff, all other things equal).

• This feature is actively worked on: check release notes. Some newer stuff is still experimental and behind feature flags, but for instance you can depend on multiple item properties with a brace syntax, as in

  // depends on feature propertyBraceExpansion
  
  Ember.Object.extend({
    items: [{ propA: 'a', propB: 'b', propC: 'c'},
            { propA: 'a2', propB: 'b2', propC: 'c2' }],
  
    // if you change either `propA` on something in `items`, or `propB`, but not
    // `propC`, the item will be removed and readded to `computed`.  When it is
    // removed you will be passed the previous value.
    computed: Ember.reduceComputed('items.@each.{propA,propB}', {
      addedItem: addedItemCallback,
      removedItem: removedItemCallback
    });
  })

• maybe give a shout-out to ember-cpm, a great place to contribute macros.

• also a shout-out to ember-enumerology which is awesome in its own right and has been upgraded to use reduce computeds.