Improve Object Model section

data/pages.yml

@@ -18,6 +18,8 @@
 - title: "The Object Model"
   url: 'object-model'
   pages:
+    - title: "Objects in Ember"
+      url: "index"
     - title: "Classes and Instances"
       url: "classes-and-instances"
     - title: "Reopening Classes and Instances"
@@ -30,8 +32,6 @@
       url: "observers"
     - title: "Bindings"
       url: "bindings"
-    - title: "Bindings, Observers, Computed Properties: What Do I Use When?"
-      url: "what-do-i-use-when"
     - title: "Enumerables"
       url: 'enumerables'
 

source/object-model/bindings.md

@@ -1,8 +1,7 @@
-A binding creates a link between two properties such that when one changes, the
-other one is updated to the new value automatically. Bindings can connect
-properties on the same object, or across two different objects. Unlike most other
-frameworks that include some sort of binding implementation, bindings in
-Ember.js can be used with any object, not just between views and models.
+Unlike most other frameworks that include some sort of binding implementation,
+bindings in Ember.js can be used with any object. That said, bindings are most
+often used within the Ember framework itself, and for most problems Ember app
+developers face, computed properties are the appropriate solution.
 
 The easiest way to create a two-way binding is to use a computed alias, that
 specifies the path to another object.

source/object-model/classes-and-instances.md

@@ -1,3 +1,7 @@
+As you learn about Ember, you'll see code like `Ember.Component.extend()` and
+`DS.Model.extend()`. Here, you'll learn about this `extend()` method, as well
+as other major features of the Ember object model.
+
 ### Defining Classes
 
 To define a new Ember _class_, call the `extend()` method on
@@ -17,10 +21,10 @@ You can also create a _subclass_ from any existing class by calling
 its `extend()` method. For example, you might want to create a subclass
 of Ember's built-in `Ember.Component` class:
 
-```app/views/person.js
-PersonView = Ember.Component.extend({
-  tagName: 'li',
-  classNameBindings: ['isAdministrator']
+```app/components/todo-item.js
+export default Ember.Component.extend({
+  classNameBindings: ['isUrgent'],
+  isUrgent: true
 });
 ```
 

source/object-model/enumerables.md

@@ -1,5 +1,3 @@
-## Enumerables
-
 In Ember.js, an Enumerable is any object that contains a number of child
 objects, and which allows you to work with those children using the
 [Ember.Enumerable](http://emberjs.com/api/classes/Ember.Enumerable.html) API. The most common
@@ -16,51 +14,37 @@ possible. This minimizes incompatibility with other libraries, and
 allows Ember.js to use the native browser implementations in arrays
 where available.
 
-For instance, all Enumerables support the standard `forEach` method:
-
-```javascript
-[1,2,3].forEach(function(item) {
-  console.log(item);
-});
-
-//=> 1
-//=> 2
-//=> 3
-```
-
-In general, Enumerable methods, like `forEach`, take an optional second
-parameter, which will become the value of `this` in the callback
-function:
-
-```javascript
-var array = [1,2,3];
-
-array.forEach(function(item) {
-  console.log(item, this.indexOf(item));
-}, array)
-
-//=> 1 0
-//=> 2 1
-//=> 3 2
-```
-
-### Enumerables in Ember.js
-
-Usually, objects that represent lists implement the Enumerable interface. Some examples:
-
- * **Array** - Ember extends the native JavaScript `Array` with the
-   Enumerable interface (unless you [disable prototype
-   extensions.](../../configuring-ember/disabling-prototype-extensions))
- * **Ember.Set** - A data structure that can efficiently answer whether it
-   includes an object.
-
-### API Overview
-
-In this guide, we'll explore some of the most common Enumerable
+## Use of Observable Methods
+
+In order for Ember to observe when you make a change to an enumerable, you need
+to use special methods that Ember.Enumerable provides. For example, if you add
+an element to an array using the standard JavaScript method `push`, Ember will
+not be able to observe the change, but if you use the Enumerable method
+`pushObject`, the change will propagate throughout your application.
+
+Here is a list of standard JavaScript array methods and their observable
+Enumerable equivalents:
+
+<table>
+  <thead>
+    <tr><th>Standard Method</th><th>Observable Equivalent</th></tr>
+  </thead>
+  <tbody>
+    <tr><td>pop</td><td>popObject</td></tr>
+    <tr><td>push</td><td>pushObject</td></tr>
+    <tr><td>reverse</td><td>reverseObjects</td></tr>
+    <tr><td>shift</td><td>shiftObject</td></tr>
+    <tr><td>unshift</td><td>unshiftObject</td></tr>
+  </tbody>
+</table>
+
+## API Overview
+
+In the rest of this guide, we'll explore some of the most common Enumerable
 conveniences. For the full list, please see the [Ember.Enumerable API
 reference documentation.](http://emberjs.com/api/classes/Ember.Enumerable.html)
 
-#### Iterating Over an Enumerable
+### Iterating Over an Enumerable
 
 To enumerate all the values of an enumerable object, use the `forEach` method:
 
@@ -76,25 +60,7 @@ food.forEach(function(item, index) {
 // Menu Item 3: Adobo Chicken
 ```
 
-#### Making an Array Copy
-
-You can make a native array copy of any object that implements
-`Ember.Enumerable` by calling the `toArray()` method:
-
-```javascript
-var states = Ember.Set.create();
-
-states.add("Hawaii");
-states.add("California")
-
-states.toArray()
-//=> ["Hawaii", "California"]
-```
-
-Note that in many enumerables, such as the `Ember.Set` used in this
-example, the order of the resulting array is not guaranteed.
-
-#### First and Last Objects
+### First and Last Objects
 
 All Enumerables expose `firstObject` and `lastObject` properties
 that you can bind to.
@@ -111,7 +77,7 @@ animals.get('lastObject');
 //=> "peacock"
 ```
 
-#### Map
+### Map
 
 You can easily transform each item in an enumerable using the
 `map()` method, which creates a new array with results of calling a
@@ -145,7 +111,7 @@ states.mapBy('capital');
 //=> ["Honolulu", "Sacramento"]
 ```
 
-#### Filtering
+### Filtering
 
 Another common task to perform on an Enumerable is to take the
 Enumerable as input, and return an Array after filtering it based on
@@ -185,7 +151,7 @@ todos.filterBy('isDone', true);
 
 If you want to return just the first matched value, rather than an Array containing all of the matched values, you can use `find` and `findBy`, which work just like `filter` and `filterBy`, but return only one item.
 
-#### Aggregate Information (All or Any)
+### Aggregate Information (All or Any)
 
 If you want to find out whether every item in an Enumerable matches some condition, you can use the `every` method:
 
@@ -223,4 +189,3 @@ Just like the filtering methods, the `every` and `some` methods have analogous `
 people.isEvery('isHappy', true) // false
 people.isAny('isHappy', true)  // true
 ```
-

source/object-model/index.md

@@ -0,0 +1,16 @@
+You'll soon notice that standard JavaScript objects aren't used widely in Ember,
+except as key-value pairs (often referred to as _hashes_). This is because
+JavaScript objects don't support the ability to observe when an object changes,
+which Ember needs to update data throughout an application.
+Ember's object model builds on standard JavaScript objects to enable this
+functionality, as well as bring several features like mixins and initialization
+to make working with them a more pleasant experience. Although these features
+aren't available in standard JavaScript, many of them are designed to align with
+proposed additions to the ECMAScript standard.
+
+In addition to bringing its own object model, Ember also extends the built-in
+JavaScript `Array` prototype with its Enumerable interface to enable it to
+observe changes and provide more features.
+
+Finally, Ember extends the `String` prototype with a few [formatting and
+localization methods](http://emberjs.com/api/classes/Ember.String.html).

source/object-model/observers.md

@@ -1,4 +1,13 @@
 Ember supports observing any property, including computed properties.
+
+Observers should contain behavior that reacts to changes in another property.
+Observers are especially useful when you need to perform some behavior after a
+binding has finished synchronizing.
+
+Observers are often over-used by new Ember developers. Observers are used
+heavily within the Ember framework itself, but for most problems Ember app
+developers face, computed properties are the appropriate solution.
+
 You can set up an observer on an object by using `Ember.observer`:
 
 ```javascript