How can I shuffle an array / hash in Ruby?

Question

In order to learn what is called? Is the object an array or hash created?

stack_of_cards = [] 

This is how I fill it:

 stack_of_cards << Card.new("A", "Spades", 1) stack_of_cards << Card.new("2", "Spades", 2) stack_of_cards << Card.new("3", "Spades", 3) ... 

Here is my map class:

 class Card attr_accessor :number, :suit, :value def initialize(number, suit, value) @number = number @suit = suit @value = value end def to_s "#{@number} of #{@suit}" end end 

I would like to shuffle the elements in this array / hash (what is called ?: S)

Any suggestions?

Answer 1

 stack_of_cards.shuffle 

This is an array, see http://www.ruby-doc.org/core-1.8.7/classes/Array.html for more information.

I wrote a functional form that returns a new array, and the new one is shuffled. Instead, you can use:

 stack_of_cards.shuffle! 

... to shuffle the array in place.

Answer 2

If you want to shuffle the hash, you can use something like this:

 class Hash def shuffle Hash[self.to_a.sample(self.length)] end def shuffle! self.replace(self.shuffle) end end 

I posted this answer since I always find this question if I search for a “ruby shuffle hash code”.

Answer 3

In addition to using the shuffle method, you can use the sort method:

 array.sort {|a, b| rand <=> rand } 

This can be useful if you are using an older version of Ruby where shuffle not implemented. As with shuffle! you can use sort! to work with an existing array.

Answer 4

If you want to go crazy and write your own shuffle method in place, you can do something like this.

  def shuffle_me(array) (array.size-1).downto(1) do |i| j = rand(i+1) array[i], array[j] = array[j], array[i] end array end 

Answer 5

For arrays:

 array.shuffle [1, 3, 2].shuffle #=> [3, 1, 2] 

For hashes:

 Hash[*hash.to_a.shuffle.flatten] Hash[*{a: 1, b: 2, c: 3}.to_a.shuffle.flatten(1)] #=> {:b=>2, :c=>3, :a=>1} #=> {:c=>3, :a=>1, :b=>2} #=> {:a=>1, :b=>2, :c=>3} # Also works for hashes containing arrays Hash[*{a: [1, 2], b: [2, 3], c: [3, 4]}.to_a.shuffle.flatten(1)] #=> {:b=>2, :c=>3, :a=>1} #=> {:c=>[3, 4], :a=>[1, 2], :b=>[2, 3]}