EmberJS - Add a computed property via method

base_menu_view.js

App.BaseMenuView = Ember.View.extend{
  statesForActiveCheck: [],
    
  init: function(){
    this._super()
    this.get('statesForActiveCheck').forEach(this.addActiveCheckMethod, this)
  },

  addActiveCheckMethod: function(statePart){
    functionName = statePart.replace('.', '_').camelize() + 'Active'; // the function name for 'account.settings' should be 'accountSettingsActive'
    this[functionName] = function(){
      return this.isActiveState(statePath);
    }.property('App.router.currentState')

    // Also tried something like this and some other variants... all the same
    //eval("this['" + functionName + "'] = function(){ return this.isActiveState('" + statePart + "')}.property('GleichklangWeb.router.currentState')")
  },

  accountEmailActive: function(){
    return false
  }.property('App.router.currentState'),


  isActiveCheckMethod: function(){
    // ....
  }
}

concrete_menu_view.js

App.ConcreteMenuView = App.BaseMenuView.extend{
  statesForActiveCheck: ['account.settings'] // Should result in an computed property 'accountSettingsActive'
}

gistfile1.txt

// When i call get() for the property 'accountSettingsActive' i get a ComputedProperty object
App.ConcreteMenuView.create().get('accountSettingsActive');
 => ComputedProperty

// But when i call get() for the initial defined property 'accountEmailActive' i get the right value back (false)
App.ConcreteMenuView.create().get('accountEmailActive');
 => false

// What am i doing wrong? 

I wrote the original Code in Coffee and ported it to js for this gist. (in case there is a lack of return calls or something... ^^ )

//is it this what you mean

Ember.computed.not = function(dependentKey) {
return Ember.computed(dependentKey, function(key) {
return !get(this, dependentKey);
});
};

Ok, plusgut from the irc-channel helped me.

The solution is:

// .....

addActiveCheckMethod: function(statePart){
    functionName = statePart.replace('.', '_').camelize() + 'Active'; // the function name for 'account.settings' should be 'accountSettingsActive'
    Em.defineProperty(this, functionName, function(){
      return this.isActiveState(statePath);
    }.property('App.router.currentState'))
  },

// ...