模板方法是一种可以在派生类上实现的方法，就像你想做的那样，然后自动调用。别担心，这是你会做很多事情的。
如果你看一下文件的源代码，你会发现它已经在那里了，但是它被分配了一个空函数。框架调用了这个空函数。如果你从一个有模板方法的类扩展，你可以“覆盖”那些方法。框架以一定的顺序调用这些方法。
Ext.app.Controller的一段源代码：

/**
 * A template method that is called when your application boots. It is called before the
 * {@link Ext.app.Application Application}'s launch function is executed so gives a hook point
 * to run any code before your Viewport is created.
 *
 * @param {Ext.app.Application} application
 *
 * @template
 */
init: Ext.emptyFn,

/**
 * A template method like {@link #init}, but called after the viewport is created.
 * This is called after the {@link Ext.app.Application#launch launch} method of Application
 * is executed.
 *
 * @param {Ext.app.Application} application
 *
 * @template
 */
onLaunch: Ext.emptyFn,