Question

Let’s say I have this code snippet running.

class Song
  def initialize(name, artist, duration)
    @name = name
    @artist = artist
    @duration = duration
  end

  def to_s
    "Song: #{@name}--#{@artist} (#{@duration})"
  end
end

SongA = Song.new("Bicyclops", "Fleck", 260)
puts SongA.to_s

If I replace SongA = Song.new("Bicyclops", "Fleck", 260) with SongA = Song.new("Bicyclops", "Fleck"), I get an error. Is this normal according to Ruby code construct?

Btw, I got the example from here. But I’m having trouble finding even after browsing through this doc. Thanks in advance for any resources you point me towards.

Answer 1

If your function definition does not specify a default value for the input parameters, you must supply them.

  # Default artist is Nobody
  # Default duration is nil
  def initialize(name, artist='Nobody', duration=nil)
    @name = name
    @artist = artist
    @duration = duration
  end

You could then initialize it omitting the properties for which you defined default values.

# Using lowercase songA instead of SongA since 
# ruby will treat the uppercase SongA as a constant...
songA = Song.new('Bicyclops')

And you don’t need to initialize all the class properties in the initialize() either. They can be added and initialized in other methods

def other_method
  @other_prop = "Another property"
end