TDD::StateCache

gistfile1.rb

#==============================================================================
# ** Module TDD::StateCache
#------------------------------------------------------------------------------
#  This module provides methods that allow a class to easily cache its method
#  calls for more dynamic state handling without using instance variables
#==============================================================================
module TDD
module StateCache
  #--------------------------------------------------------------------------
  # * State Cache Store
  #--------------------------------------------------------------------------
  def state_cache
    @state_cache ||= {}
  end
  #--------------------------------------------------------------------------
  # * Set Cache for Calling Method
  #--------------------------------------------------------------------------
  def set_cache(object)
    state_cache[key] = object
    return state_cache[key]
  end
  #--------------------------------------------------------------------------
  # * Check Cache for Calling Method
  #--------------------------------------------------------------------------
  def cache
    return state_cache[key]
  end
  #--------------------------------------------------------------------------
  # * Get Calling Method as Key String
  #--------------------------------------------------------------------------
  def key
    caller[1][/`.*'/][1..-2]
  end
end
end

Example of use:

#--------------------------------------------------------------------------
# Get Background Sprite
#--------------------------------------------------------------------------
def background_sprite
  return cache if cache

  background_sprite = Sprite.new
  # Setup other visual properties like blt bitmap etc

  return set_cache background_sprite
end

Whenever you want to access the background_sprite, whether that be for moving it or what have you, you call the background_sprite method. Whenever you need to clear the background sprite, you can do:

state_cache.delete("background_sprite")

When you want to clear all cached objects, you can of course do:

state_cache.clear

If you want to, like me, redraw all these cached objects when a data model update has happened, just do state_cache.clear and make sure that you call the relevant objects in the next frame. Easy; no need to recall a setup method. You don't even need a setup method.

And when the class itself is disposed and set to nil, of course all its objects will to. The benefit of this is that you can call background_sprite anywhere; order doesn't matter. You don't have to set up @background_sprite somewhere first, then call it when you need to access, say, its width. No, you just call background_sprite when you need it; if it doesn't exist, it gets made. This takes a page from the book of Functional Programming by being stateless.