(Reduce)Computed

functional big data transclusion in the browser

@jonnii

What is the best

feature of ember?

Routing?

Maybe...

Ember.Select?

Hahahahahaha. NO.

Computed Properties!!

Seriously, they are magic.

You know you can do this...

http://jsfiddle.net/NQKvy/319/

Did you know you can do this?

http://jsfiddle.net/BvsEY/2/

Computed Properties just reduced.

This is how I discovered reduce computed...

What is reduce computed?

A reduce computed is a computed property which

observes the state of an array and reduces it

into a single value...

e.g.

Ember.computed.min

Ember.computed.max

It's the reduce part of map reduce. a.k.a Big Data.

Reduce Computed

initialValue
options
addedItem
removedItem

 Ember.computed.max = function (dependentKey) {
  return Ember.reduceComputed.call(null, dependentKey, {
    initialValue: -Infinity,

    addedItem: function (accumulatedValue, item, changeMeta, instanceMeta) {
      return Math.max(accumulatedValue, item);
    },

    removedItem: function (accumulatedValue, item, changeMeta, instanceMeta) {
      if (item < accumulatedValue) {
        return accumulatedValue;
      }
    }
  });
};

The secret sauce...

xxItem: function (accumulatedValue, item, changeMeta, instanceMeta) {
  ... magic ...    
},

changeMeta
index
item
arrayChanged
property

instanceMeta
A scratch pad for storing
reduce computed state

Example Sum/Avg

http://jsfiddle.net/NQKvy/326/

Array Computed

Same as reduce computed except:

Result is an array
Result is kept up to date

For:

Filtering
Sorting

Group Example

http://jsfiddle.net/d82yd/5/

What next?

https://github.com/jamesotron/ember-enumerology

https://github.com/jamesarosen/ember-cpm

Feature actively being worked on

Someone please rewrite Ember.Select

Plugs

Code Now

http://codenow.org/

I'm hiring...