科学编程/SwayPresentations/对象/变差传承

变差传承

变差传承：子类改变了超类的行为。

   function super()
       {
       var greeting = "hello";
       function a() { greeting; }
       this;
       }
   
   function sub()
       {
       function a() { "well, " + a . prior() + " there!"; }
       extends(super());
       }
   
   var s = sub();
   
   println(s . a());

输出是

   well, hello there!

查看s对象会返回

   <OBJECT 2611>:
       context: <OBJECT 654>
       dynamicContext: <OBJECT 654>
       callDepth: 1
       constructor: <function sub()>
       this: <OBJECT 2611>
       a: <function a()>
       a: <function a()>
       greeting: "hello"

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