如何在Ruby中调用super.super方法

Question

I have the following classes

class Animal
  def move
    "I can move"
  end
end

class Bird < Animal
  def move
    super + " by flying"
  end
end

class Penguin < Bird
  def move
    #How can I call Animal move here
    "I can move"+ ' by swimming'
  end
end

How can I call Animal's move method inside Penguin ? I can't use super.super.move. What are the options?

Thanks

Answer 1

You can get the move instance method of Animal , bind it to self , then call it:

class Penguin < Bird
  def move
    m = Animal.instance_method(:move).bind(self)
    m.call
  end
end

Answer 2

class Penguin < Bird
  def move
    grandparent = self.class.superclass.superclass
    meth = grandparent.instance_method(:move)
    meth.bind(self).call + " by swimming"
  end
end

puts Penguin.new.move

For more details about this approach read this answer

Answer 3

You could do this (which I suggested here ):

class Penguin < Bird
  def move
    puts self.class.ancestors[2].instance_method(__method__).bind(self).call +
    ' by swimming'
  end
end

Penguin.new.move
  # I can move by swimming

[Edit: I see this is quite similar to @August's answer. This has the slight advantage that neither the class Animal nor method name move are hard-wired.]

Answer 4

If you are using Ruby 2.2.0, then you have something new in your plate. That something is : Method#super_method .

class Animal
  def move
    "I can move"
  end
end

class Bird < Animal
  def move
    super + " by flying"
  end
end

class Penguin < Bird
  def move
    method(__method__).super_method.super_method.call + ' by swimming'
  end
end

Penguin.new.move # => "I can move by swimming"

I completely agree with Robert Klemme's and his answer is best and clean.