Ruby: overriding the puts method

问题

I've got a small program meant to be run in IRB. It ultimately outputs something that looks like an array, though technically isn't an array. (The class inherits from array.) The problem is, when I do an instance of this class, e.g. example = Awesome.new(1,2,3), and I write "puts example", IRB's default behavior is to put each element of example onto it's own line.

So instead of

[1,2,3]

(which is what I want), IRB pops out this.

1
2
3

Is there a smart way to override the puts method for this special class? I tried this, but it didn't work.

def puts
  self.to_a
end

Any idea what I'm doing wrong?

Update: So I tried this, but no success.

def to_s
  return self
end

So when I'm in IRB and I just type "example", I get the behavior I'm looking for (i.e. [1, 2, 3]. So I figured I could just to return self, but I'm still messing up something, apparently. What am I not understanding?

回答1:

def puts(o)
  if o.is_a? Array
    super(o.to_s)
  else
    super(o) 
  end  
end

puts [1,2,3] # => [1, 2, 3]

or just use p:

p [1, 2, 3] # => [1, 2, 3]

回答2:

You should override to_s and it will be handled automatically, just remember to return a string from to_s and it will work as a charm.

Example snippet..

class Obj 
  def initialize(a,b)
    @val1 = a 
    @val2 = b 
  end 

  def to_s
    "val1: #@val1\n" +
    "val2: #@val2\n" 
  end 
end

puts Obj.new(123,321);

val1: 123
val2: 321

回答3:

You probably would be better off implementing to_ary method for your Array-like class. This method will be called by puts to obtain all the elements. I posted a snippet from one of my projects below

require 'forwardable'

class Path 
  extend Forwardable
  def_delegators :@list, :<<, :count, :include?, :last, :each_with_index, :map

  def initialize(list = [])
    @list = list
  end

  def to_ary
    self.map.each_with_index{ |e, i| "#{e}, step: #{i}" }
  end
end

来源：https://stackoverflow.com/questions/11463873/ruby-overriding-the-puts-method

标签

ruby

irb