object.lua

-- some notes:
-- Component functions are Hookified
-- 'add' is reserved as a function name, for adding Components to the Object
-- Object doesn't call init() for Components, you have to do that once they are all added
-- private functions should be local to the Component's module, as there is no way to make a member function private to the Component

local Hook = require('hook')

local C = Class()


-- components are just tables with functions in them, with a metatable for type checking

local ComponentMT = {}
function C.Component()
   return setmetatable({}, ComponentMT)
end

local function isComponent(c)
   return getmetatable(c) == ComponentMT
end


function C:init()
   self.hooks = {}
   self.warned = {}
end

function C:add(comp)
   assert(isComponent(comp), 'argument must be an Object.Component')
   
   for name, value in pairs(comp) do
      if type(value) == 'function' then
         if not self.hooks[name] then
            self.hooks[name] = Hook(name)
         end
         self.hooks[name]:register(value)
         
      else
         error('Component with non-function value: '..name)
      end
   end
end

function C:call(name, ...)
   local hook = self.hooks[name]
   if not hook then
      if not self.warned[name] then
         print('Warning: hook called with no registered functions: ' .. name)
         self.warned[name] = true
      end
      return
   end

   return hook(self, ...)
end

return C