如何执行回调函数是一个自定义Dojo模块?

I have the code below:

我有下面的代码:

define(["dojo/_base/declare"],function (declare) {
   return declare("tamoio.Map", null, {

     methodA: function(param){
        console.log(param);
        this.methodB('xxx',function(){
          this.methodC(); //it didn't call!
        });
     },

     methodB: function(text, callback){
       alert('do nothing: ' + text);
       callback();
     },

     methodC: function(){
       alert('hello');
     }

   });
});
define(["do