Ruby setting default hash value

Question

Here is a test that I am trying to pass:

def test_it_scores_a_double_word_score
    play = Play.new(:word => "hello")
    assert_equal 16, play.score(:word_multiplier => :double)
  end

Here is my class:

class Play < ActiveRecord::Base

  before_save { self.word = word.downcase }

  validates :word, presence: true, length: { maximum: 7 }

  def letter_scores
    {"A"=>1, "B"=>3, "C"=>3, "D"=>2, "E"=>1, "F"=>4, "G"=>2, "H"=>4, "I"=>1, "J"=>8,
     "K"=>5, "L"=>1, "M"=>3, "N"=>1, "O"=>1, "P"=>3, "Q"=>10, "R"=>1, "S"=>1, "T"=>1,
     "U"=>1, "V"=>4, "W"=>4, "X"=>8, "Y"=>4, "Z"=>10}
  end

  def score(word_multiplier: :single)
    word_multiplier = {:single => 1, :double => 2, :triple => 3}

    word.upcase.chars.inject(0){|sum, letter| sum + letter_scores[letter]} * word_multiplier
  end
end

So my idea is that I need the default value of the hash to be :single. If the key/value pair of :word_multiplier => :double is passed, then I need the the hash to return 2.

I have syntax problems: 1) I have only set defaults in methods using the = sign, not hashes. How does one do this?

2) I put in word_multiplier: :single in the parenthesis which seems to work in setting a default. But :word_multiplier => :single doesn't work. What is going on?

Brennan · Accepted Answer · 2015-01-26 18:33:33Z

1

Why are you using a symbol/enum scheme to set the multiplier? I'd just stick to a number:

def score(word_multiplier = 1)
  word.upcase.chars.inject(0){|sum, letter| sum + letter_scores[letter]} * word_multiplier
end

If you don't pass the method a multiplier, it will default to 1

If you do need to use a hash default parameter, you do it the same way you would any other type:

def my_method(options = {:multiplier => :single})
  multipliers = {:single => 1, :double => 2, :triple => 3}
  word_multiplier = multipliers[options[:multiplier]]
end

answered Jan 26, 2015 at 18:33

Brennan

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mushishi78 · Accepted Answer · 2015-01-26 18:34:15Z

1

What you're doing is assigning a default to word_multiplier as an argument and then reassigning word_multilier to the hash, without using the argument passed in. The quickest way to fix this, would look like this:

word_multiplier = {:single => 1, :double => 2, :triple => 3}[word_multiplier]

Nb. I'd avoid using the keyword arguments if you want people to use your code until people stop using Ruby 1.8.7 and Ruby 1.9.3.

answered Jan 26, 2015 at 18:34

mushishi78

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