Making a Ruby block return an array?

Question

I've made a small DSL-like program for adding drinks to an array. It's a pretty basic example for using instance_eval and &block to create a quick program.

Here's the program:

class Drinks
  def initialize(&block) # Initialize drinks
    @drinks = []
    instance_eval &block
  end

  def drink(d)
    @drinks << d
  end # Add drink

  def all_drinks
    puts @drinks
  end

end

add_drinks = Drinks.new do
  drink "water"
  drink "soda"
  drink "juice"
end

add_drinks.all_drinks

The plan is to make add_drinks auto-return itself so you don't have to use add_drinks.all_drinks. Would this be possible? Thanks.

"auto-return itself"? But that's not what you want, you want the array? — Dave Newton
– Dave Newton, Commented Apr 14, 2012 at 14:34

mikdiet · Accepted Answer · 2012-04-14 14:37:18Z

5

You can inherit Drinks from Array, so you can work with new instance as with array

class Drinks < Array
  def initialize(&block) # Initialize drinks
    instance_eval &block
  end

  def drink(d)
    self << d
  end # Add drink
end

add_drinks = Drinks.new do
  drink "water"
  drink "soda"
  drink "juice"
end

add_drinks  #  => ["water", "soda", "juice"]

answered Apr 14, 2012 at 14:37

mikdiet

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1 Comment

Thermatix Over a year ago

I realise this is off topic but I'd just like to say that this helped me fix a problem and make my code less verbose + simpler so thanks, I don't know why but I didn't consider doing the instance_eval inside of the initializer rather then outside of it in the constructor so thanks.

seph · Accepted Answer · 2012-04-14 15:01:40Z

1

You might want to rethink what the object is and how it behaves. Maybe do it like this:

class Drinks
  def initialize(&block)
    @drinks = []
    instance_eval &block
  end

  def add(d)
    @drinks << d
  end

  def show
    puts @drinks
  end
end

drinks = Drinks.new do
  add "water"
  add "soda"
  add "juice"
end

drinks.show

answered Apr 14, 2012 at 15:01

seph

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