What is the most efficient way to initialize a Class in Ruby with different parameters and default values?

Question

I would like to have a class and some attributes which you can either set during initialization or use its default value.

class Fruit
  attr_accessor :color,         


        

Answer 1

Brian's answer is excellent but I would like to suggest some modifications to make it mostly meta:

class Fruit

  # Now this is the only thing you have to touch when adding defaults or properties
  def set_defaults
    @color ||= 'green'
    @type  ||= 'pear'
  end

  def initialize(params = {})
    params.each { |key,value| instance_variable_set("@#{key}", value) }
    set_defaults
    instance_variables.each {|var| self.class.send(:attr_accessor, var.to_s.delete('@'))}
  end

  def to_s
    instance_variables.inject("") {|vars, var| vars += "#{var}: #{instance_variable_get(var)}; "}
  end

end

puts Fruit.new
puts Fruit.new :color => 'red', :type => 'grape'  
puts Fruit.new :type => 'pomegranate'
puts Fruit.new :cost => 20.21
puts Fruit.new :foo => "bar"


f = Fruit.new :potato => "salad"
puts "f.cost.nil? #{f.cost.nil?}"

Which outputs:

@color: green; @type: pear; 
@color: red; @type: grape; 
@color: green; @type: pomegranate; 
@color: green; @type: pear; @cost: 20.21; 
@color: green; @type: pear; @foo: bar; 
f.cost.nil? true

Of course this wouldn't be a perfect solution for everything but it gives you some ideas on making your code more dynamic.