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 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 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...
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