Ruby Language Methods Default parameters
Example
def make_animal_sound(sound = 'Cuack')
puts sound
end
make_animal_sound('Mooo') # Mooo
make_animal_sound # Cuack
It's possible to include defaults for multiple arguments:
def make_animal_sound(sound = 'Cuack', volume = 11)
play_sound(sound, volume)
end
make_animal_sound('Mooo') # Spinal Tap cow
However, it's not possible to supply the second without also supplying the first. Instead of using positional parameters, try keyword parameters:
def make_animal_sound(sound: 'Cuack', volume: 11)
play_sound(sound, volume)
end
make_animal_sound(volume: 1) # Duck whisper
Or a hash parameter that stores options:
def make_animal_sound(options = {})
options[:sound] ||= 'Cuak'
options[:volume] ||= 11
play_sound(sound, volume)
end
make_animal_sound(:sound => 'Mooo')
Default parameter values can be set by any ruby expression. The expression will run in the context of the method, so you can even declare local variables here. Note, won't get through code review. Courtesy of caius for pointing this out.
def make_animal_sound( sound = ( raise 'TUU-too-TUU-too...' ) ); p sound; end
make_animal_sound 'blaaaa' # => 'blaaaa'
make_animal_sound # => TUU-too-TUU-too... (RuntimeError)
