Javascript scope issues

I am extending dojo's dojox.data.JsonRestStore and I want to provide my own fixed scheme. this is getUsername won't work because it doesn't refer to the current datastore Take a look at this code:

/**
 * @author user
 */
dojo.provide("cms.user.UserAuthenticationStore");

dojo.require("dojox.data.JsonRestStore");

dojo.declare("cms.user.UserAuthenticationStore", [dojox.data.JsonRestStore], {
    schema: {
        prototype: {
            getUsername: function(){
                return ???.getValue(this, "username");
            }
        }
    }
});

Can you tell me what to replace ??? with?

EDIT:

Here's the code that works but it's ugly as hell, can someone tell me how to fix this?

/**
 * @author user
 */
dojo.provide("cms.user.UserAuthenticationStore");

dojo.require("dojox.data.JsonRestStore");

dojo.declare("c开发者_开发百科ms.user.UserAuthenticationStore", [dojox.data.JsonRestStore], {
    schema: {
        prototype: {}
    },
    constructor: function(){
        var that = this;
        this.schema.prototype.getUsername = function(){
            return that.getValue(this, "username");
        }
    }
});

Instead of:

this.schema.prototype.getUsername = function() {
  return ???.getValue(this, "username");
}

You can try:

this.schema.prototype.getUsername = dojo.hitch(this, "getValue", <this>, "username");

where "<this>" is the variable being used as the first parameter of the getValue function. Otherwise, your "that" isn't too ugly, but people usually call it "self" or something.

Edit:

Maybe this will work? Quick and dirty way to create a new schema. Otherwise, you might want to create another component that defines your own scheme separately. Then you can just create a "new MySChema()" as the "schema" var.

dojo.declare("cms.user.UserAuthenticationStore", [dojox.data.JsonRestStore], {
    self: this,
    schema:  new (function() {
                this.getUsername = function () { return self.getValue(this, "username"); }
             }
    })();
});

Here's the right way to do this:

/**
 * @author user
 */
dojo.provide("cms.user.UserAuthenticationStore");

dojo.require("dojox.data.JsonRestStore");

dojo.declare("cms.user.UserAuthenticationStore", [dojox.data.JsonRestStore], {
    schema: {
        prototype: {
            store: null,
            getUsername: function(){
                return this.store.getValue(this, "username");
            }
        }
    },
    constructor: function(){
        this.schema.prototype.store = this;
    },
    login: function(){

    },
    logout: function(){

    }
});