了解Ruby方法参数语法

Question

I've been following an RSpec tutorial on Pluralsight for creating a basic card game. When the class is defined as such:

class Card
  def initialize(suit:, rank:)
    @suit = suit
    @rank =
      case rank
      when :jack then 11
      when :queen then 12
      when :king then 13
      else rank
      end
  end
end

the RSpec test code is for example:

RSpec.describe 'a playing card' do
  it 'has a suit' do
    raise unless Card.new(suit: :spades, rank: 4).suit == :spades
  end
end

I haven't encountered method parameter syntax like this (suit: :spades, rank: 4) . Can someone explain what this means, or point me in the right direction on where to look this up?

Answer 1

It's called keyword arguments . Unlike positional arguments , you can pass them in any order, but you have to provide their names. This can greatly improve readability, especially for methods with higher arity. More on the subject