Programming Crystal

Converting a Ruby Class to Crystal

If you’re a Ruby developer, converting classes is a place where the differences between the languages are especially visible. Walking through the transition from Ruby to Crystal with explanations of the error messages along the way can make it easier to see how Crystal’s use of types changes the story. (If you’re not a Ruby developer, feel free to skip to the next section.)

Here’s a simple class in Ruby:

classes_and_structs/mineral.rb

class Mineral
  attr_reader :name, :hardness, :crystal_struct

  def initialize(name, hardness, crystal_struct)
    @name = name
    @hardness = hardness
    @crystal_struct = crystal_struct
  end
end

def mineral_with_crystal_struct(crstruct, minerals)
 minerals. ...