Create on use

lazyobject.rb

# Class to easily instantiate an object when needed.
# Similar to using (object ||= Foo.new).bar, but stores the initialization code to make
# the code cleaner.
class LazyObject
  @object = nil
  def initialize(&code)
    @init = code
  end

  def was_initialized?
    not @object.nil?
  end

  def method_missing(m, *args, &block)
    if not was_initialized? then
      @object = @init.call
      @object.public_methods(false).each do |meth|
        (class << self; self; end).class_eval do
          define_method meth do |*args|
            @object.send meth, *args
          end
        end
      end
      @object.send m, *args, &block
    else
      super.method_missing m, *args, &block
    end
  end
end

if __FILE__ == $0 then
  # This is a bit of a forced use-case, LazyObject was created to reduce
  # time spent creating unused, heavy-weight objects, e.g. RMagick's Image
  # classes from file.
  a = LazyObject.new { Array.new ["foo"] }
  a << "bar" if rand >= 0.5
  if a.was_initialized?
    puts a.inspect
  else
    puts "Did not initialize object!"
  end
end