middleclass/middleclass.lua

local middleclass = {
  _VERSION     = 'middleclass v3.2.0',
  _DESCRIPTION = 'Object Orientation for Lua',
  _URL         = 'https://github.com/kikito/middleclass',
  _LICENSE     = [[
    MIT LICENSE

    Copyright (c) 2011 Enrique García Cota

    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the
    "Software"), to deal in the Software without restriction, including
    without limitation the rights to use, copy, modify, merge, publish,
    distribute, sublicense, and/or sell copies of the Software, and to
    permit persons to whom the Software is furnished to do so, subject to
    the following conditions:

    The above copyright notice and this permission notice shall be included
    in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
    OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
    IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
    CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
    TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
    SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  ]]
}

local _metamethods = {}
for m in ([[ add band bor bxor bnot call concat div eq
             gc index ipairs idiv le len lt metatable mod mode
             mul newindex pairs pow shl shr sub tostring unm ]]):gmatch("%S+") do
  _metamethods['__' .. m] = true
end

local function _setClassDictionariesMetatables(aClass)
  local dict = aClass.__instanceDict
  aClass.__instanceMeta.__index = dict

  local super = aClass.super
  if super then
    local superStatic = super.static
    setmetatable(dict, { __index = super.__instanceDict })
    setmetatable(aClass.static, { __index = function(_,k) return rawget(dict,k) or superStatic[k] end })
  else
    setmetatable(aClass.static, { __index = function(_,k) return dict[k] end })
  end
end

local function _createIndexWrapper(aClass, f)
  if f == nil then
    return aClass.__instanceDict
  else
    return function(self, key)
      local value = aClass.__instanceDict[key]

      if value ~= nil then
        return value
      elseif type(f) == "function" then
        return (f(self, key))
      else
        return f[key]
      end
    end
  end
end

local function _setMetamethod(aClass, name, f)
  if name == "__index" then
    f = _createIndexWrapper(aClass, f)
  end

  aClass.__instanceMeta[name] = f
end

local function _propagateMetamethod(aClass, name, f)
  _setMetamethod(aClass, name, f)

  for subclass in pairs(aClass.subclasses) do
    if rawget(subclass.__instanceDict, name) == nil then
      _propagateMetamethod(subclass, name, f)
    end
  end
end

local function _updateClassDict(aClass, key, value)
  aClass.__instanceDict[key] = value

  if _metamethods[key] then
    if value == nil then
      if aClass.super then
        value = aClass.super.__instanceDict[key]
      end
    end

    _propagateMetamethod(aClass, key, value)
  end
end

local function _setClassMetatable(aClass)
  setmetatable(aClass, {
    __tostring = function() return "class " .. aClass.name end,
    __index    = aClass.static,
    __newindex = _updateClassDict,
    __call     = function(self, ...) return self:new(...) end
  })
end

local function _createClass(name, super)
  local aClass = { name = name, super = super, static = {}, __instanceDict = {}, __instanceMeta = {} }
  aClass.subclasses = setmetatable({}, {__mode = "k"})

  _setClassDictionariesMetatables(aClass)
  _setClassMetatable(aClass)

  return aClass
end

local function _setSubclassMetamethods(aClass, subclass)
  for m in pairs(_metamethods) do
    _setMetamethod(subclass, m, aClass.__instanceDict[m])
  end
end

local function _setDefaultInitializeMethod(aClass, super)
  aClass.initialize = function(instance, ...)
    return super.initialize(instance, ...)
  end
end

local function _includeMixin(aClass, mixin)
  assert(type(mixin)=='table', "mixin must be a table")
  for name,method in pairs(mixin) do
    if name ~= "included" and name ~= "static" then aClass[name] = method end
  end
  if mixin.static then
    for name,method in pairs(mixin.static) do
      aClass.static[name] = method
    end
  end
  if type(mixin.included)=="function" then mixin:included(aClass) end
end

local Object = {
  __tostring   = function(self) return "instance of " .. tostring(self.class) end,
  initialize   = function(self) end,
  isInstanceOf = function(self, aClass)
    return type(self)                == 'table' and
           type(self.class)          == 'table' and
           type(aClass)              == 'table' and
           ( aClass == self.class or
             type(aClass.isSubclassOf) == 'function' and
             self.class:isSubclassOf(aClass)
           )
  end,

  static = {

    allocate = function(self)
      assert(type(self) == 'table', "Make sure that you are using 'Class:allocate' instead of 'Class.allocate'")
      return setmetatable({ class = self }, self.__instanceMeta)
    end,

    new = function(self, ...)
      local instance = self:allocate()
      instance:initialize(...)
      return instance
    end,

    subclass = function(self, name)
      assert(type(self) == 'table', "Make sure that you are using 'Class:subclass' instead of 'Class.subclass'")
      assert(type(name) == "string", "You must provide a name(string) for your class")

      local subclass = _createClass(name, self)
      _setSubclassMetamethods(self, subclass)
      _setDefaultInitializeMethod(subclass, self)
      self.subclasses[subclass] = true
      self:subclassed(subclass)

      return subclass
    end,

    subclassed = function(self, other) end,

    isSubclassOf = function(self, other)
      return type(other)                   == 'table' and
             type(self)                    == 'table' and
             type(self.super)              == 'table' and
             ( self.super == other or
               type(self.super.isSubclassOf) == 'function' and
               self.super:isSubclassOf(other)
             )
    end,

    include = function(self, ...)
      assert(type(self) == 'table', "Make sure you that you are using 'Class:include' instead of 'Class.include'")
      for _,mixin in ipairs({...}) do _includeMixin(self, mixin) end
      return self
    end
  }
}

function middleclass.class(name, super)
  assert(type(name) == 'string', "A name (string) is needed for the new class")
  if super then return super:subclass(name) end
  local subclass = _createClass(name)
  _includeMixin(subclass, Object)
  return subclass
end

middleclass.Object = Object

setmetatable(middleclass, { __call = function(_, ...) return middleclass.class(...) end })

return middleclass