datastore.lua

DataStore = {
	data = {},
	subscribers = {}
}
function DataStore:new (o)
	o = o or {}   -- create object if user does not provide one
	setmetatable(o, self)
	self.__index = self
	return o
end

function DataStore:get( key )
	return self.data[key]
end

function DataStore:set( key, value )
	oldvalue = self.data[key]
	self.data[key] = value
	if self.subscribers[key] then
		for i,v in ipairs(self.subscribers[key]) do
			v(oldvalue, value)
		end
	end
end

function DataStore:subscribe( key, callback )
	s = self.subscribers[key] or {}
	table.insert(s, callback)
	self.subscribers[key] = s
end