Ruby-重载方法

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在子类里,我们可以通过重载父类方法来改变实体的行为.

ruby> class Human

   |   def identify

   |     print "I'm a person.\n"

   |   end

   |   def train_toll(age)

   |     if age < 12

   |       print "Reduced fare.\n";

   |     else

   |       print "Normal fare.\n";

   |     end

   |   end

   | end

  nil

ruby> Human.new.identify

I'm a person.

  nil

ruby> class Student1<Human

   |   def identify

   |     print "I'm a student.\n"

   |   end

   | end

  nil

ruby> Student1.new.identify

I'm a student.

  nil  

如果我们只是想增强父类的 identify 方法而不是完全地替代它,就可以用 super.

ruby> class Student2<Human

   |   def identify

   |     super

   |     print "I'm a student too.\n"

   |   end

   | end

  nil

ruby> Student2.new.identify

I'm a human.

I'm a student too.

  nil  

super 也可以让我们向原有的方法传递参数.这里有时会有两种类型的人...v

ruby> class Dishonest<Human

   |   def train_toll(age)

   |     super(11) # we want a cheap fare.

   |   end

   | end

  nil

ruby> Dishonest.new.train_toll(25)

Reduced fare. 

  nil

ruby> class Honest<Human

   |   def train_toll(age)

   |     super(age) # pass the argument we were given

   |   end

   | end

  nil

ruby> Honest.new.train_toll(25)

Normal fare. 

  nil