Deprecation Guide for Computed Properties With a Shared Getter And Setter

Ember.js 1.12 introduces an improved syntax for computed properties with a setter. Previously, computed properties with a setter implemented that setter by inspecting the number of arguments passed to the computed property's descriptor.

For example, this computed property splits a full name into two parts when set:

  fullName: Ember.computed("firstName", "lastName", function(key, newName) {
    if (arguments.length > 1) {
      var parts = newName.split(" ");
      this.setProperties({ firstName: parts[0], lastName: parts[1] });
      return newName;
    } else {
      return this.get("firstName") + " " + this.get("lastName");
    }
  });

These uses should be converted to use the new discrete getter and setter syntax introduced in 1.12:

  fullName: Ember.computed("firstName", "lastName", {
    get: function() {
      return this.get("firstName") + " " + this.get("lastName");
    },
    set: function(key, newName) {
      var parts = newName.split(" ");
      this.setProperties({ firstName: parts[0], lastName: parts[1] });
      return newName;
    }
  });

For further reading, review the RFC describing this feature and the pull request of the initial implementation.