For any ruby devs out there, wanted to share a neat little open-source module I wrote to solve a common problem. Keep in mind ruby is not my main language so if there is a batter approach here I'm all ears.

Basically right now I have a game (text based mud) and in normal and expected fashion objects in the game are created when their objects get initialized, such as a new player being created. The system then periodically saves the universe by marshalling all the object into some serialized format and saves it to a file from time to time. As tends to be the case with serialization, however, when an object is restored, such as a previous player logging out and back in, then the class is created directly without the initialize method getting called , its class and instance variables are simply populated directly.

This is where problems can arise if you change the system and add new features (such as a new variable to an object). New objects that are created will populate the new variable correctly through the initialize method however already existing players will not have that variable set at all (it won't be nil, it simply wont be set, which is a distinctly different state). This is the problem I solved.

What I did was created a mix-in module that lets you set default values for variables, once a class is reinstated from storage it checked if any variables that have defaults are unset (nil variables are considered set) and then applies the default value to them. In this way legacy objects will be able to update to new code changes automatically when it loads. To prevent duplicating code you can even intentionally leave it out of the initialize method and rely on the defaults when it is appropriate to do so.

Moreover the defaults do not have to be static values but can be determined based on the existing state of the object, which makes them dynamic and flexible... a class that uses the mixin could look like this:

require 'defaults'

class Foo
include Defaults

# @bar defaults to @baz*2
default(:bar) { |this| this.baz * 2 }
# @faaboo defaults to 178
default(:faaboo) { 178 }

def initialize
@baz = 13

#this line can be ommited
@bar = 26
# if you add this line instead
load_defaults
#either work fine
end
end

Here is a link to the module:

https://git.qoto.org/aethyr/Aethyr/-/blob/master/lib/aethyr/core/util/defaults.rb

You can see a class that utilizes this new feature here:

https://git.qoto.org/aethyr/Aethyr/-/blob/master/lib/aethyr/core/objects/game_object.rb

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