Ember.js how does reopenClass work?

Question

I don\'t really get the function of ember.js\' reopenClass. I thought it added extra code to the Object\'s prototype, so all instances of that Object would get the functiona

Answer 1

reopen changes prototype and thus changes instances of a class

reopenClass changes the constructor itself and thus changes the class by creating static properties and functions that are only available on the class but not on any instances of the class.

Note that the changes introduced by reopen only take effect after calling .create()

Code examples based on the doc:

http://emberjs.com/api/classes/Ember.Application.html#method_reopen

MyObject = Ember.Object.extend({
  name: 'an object'
});

o = MyObject.create();
o.get('name'); // 'an object'

MyObject.reopen({
  say: function(msg){
    console.log(msg);
  }
})

try{
    o.say("hey");
} catch(e) {
    console.log(e); // o.say is not a function (...yet)
}
o2 = MyObject.create();
o2.say("hello"); // logs "hello"

o.say("goodbye"); // logs "goodbye"

http://emberjs.com/api/classes/Ember.Application.html#method_reopenClass

MyObject = Ember.Object.extend({
  name: 'an object'
});

MyObject.reopenClass({
  canBuild: false
});

MyObject.canBuild; // false
o = MyObject.create();
o.canBuild; // undefined