1.Then, when the function delegate is invoked the specified method of the specified instance is called.
接着,调用此函数委托时,将调用指定实例的指定方法。
2.procedure name. When the specified procedure is an instance method then the function delegate refers to both the instance and the method.
如果指定的过程是实例方法,则此函数委托同时引用此实例和方法。