Simple computed Attribute

person.js

YUI().use("attribute", "attribute-computable", function (Y) {

  function Person(options) {
    var defaultAttrs = {
      firstName : {
        value: "John"
      },

      lastName  : {
        value: "Doe"
      },

      fullName  : {
        // Possibly default to true if `attribute-computable` is used?
        computed: true,

        // `getter` is evaluated upon instantiation. If getter uses `this.get(attr)`,
        // then subscriptions are set up from this attribute to those attributes.
        getter: function () {
          return this.get('firstName') + ' ' + this.get('lastName');
        },

        setter: function (value) {
          var lastSpacePos = value.lastIndexOf(" ");
          if (lastSpacePos > 0) { // Ignore values with no space character
            this.set('firstName', value.substring(0, lastSpacePos)); 
            this.set('lastName', value.substring(lastSpacePos + 1));
          }
        }
      }
    };

    this.addAttrs(defaultAttrs, options);
  }

  Y.augment(Person, Y.Attribute);