Added initial version of MindState.lua

MindState.lua

@@ -0,0 +1,134 @@
+-----------------------------------------------------------------------------------
+-- MindState.lua
+-- Enrique García ( enrique.garcia.cota [AT] gmail [DOT] com ) - 19 Oct 2009
+-- Based on Unrealscript's stateful objects
+-----------------------------------------------------------------------------------
+
+require 'MiddleClass.lua'
+--[[ StatefulObject declaration
+  * Stateful classes have a list of states (accesible through class.states).
+  * When a method is invoked on an instance of such classes, it is first looked up on the class current state (accesible through class.currentState)
+  * If a method is not found on the current state, or if current state is nil, the method is looked up on the class itself
+  * It is possible to change states by doing class:gotoState(stateName)
+]]
+StatefulObject = class('StatefulObject')
+
+StatefulObject.states = {} -- the root state list
+
+-- Instance methods
+
+--[[ constructor
+  If your states need initialization, they can receive parameters via the initParameters parameter
+  initParameters is a table with parameters used for initializing the states. These are needed mostly if
+  your states have a custom superclass that needs parameters on their initialize() function.
+]]
+function StatefulObject:initialize(initParameters)
+  super(self)
+  initParameters = initParameters or {} --initialize to empty table if nil
+  self.states = {}
+  for stateName,stateClass in pairs(self.class.states) do 
+    local state = stateClass:new(unpack(initParameters[stateName] or {}))
+    state.name = stateName
+    self.states[stateName] = state
+  end
+end
+
+--[[ Changes the current state.
+  If the current state has a method called onExitState, it will be called, with the instance as a parameter.
+  If the "next" state exists and has a method called onExitState, it will be called, with the instance as a parameter.
+  use gotoState(nil) for setting states to nothing
+  This method invokes the exitState and enterState functions if they exist on the current state
+]]
+function StatefulObject:gotoState(stateName)
+  assert(self.states~=nil, "Attribute 'states' not detected. check that you called instance:gotoState and not instance.gotoState, and that you invoked super(self) in the constructor.")
+
+  local nextState = self.states[stateName]
+  assert(type(stateName)=='string' and nextState~=nil, "State '" .. stateName .. "' not found")
+
+  local prevState = self.currentState
+  if(prevState~=nil and type(prevState.exitState) == "function") then
+    prevState.exitState(self)
+  end
+
+  self.previousState = prevState
+  self.currentState = nextState
+
+  if(nextState~=nil and type(nextState.enterState) == "function") then
+    nextState.enterState(self)
+  end
+end
+
+-- Class methods
+
+--[[ Adds a new state to the "states" class member.
+  superState is optional. If nil, Object will be the parent class of the new state
+  returns the newly created state
+]]
+function StatefulObject:addState(stateName, superState)
+  assert(subclassOf(StatefulObject, self), "Use class:addState instead of class.addState")
+  assert(self.states[stateName]==nil, "The class " .. self.name .. " already has a state called '" .. stateName)
+  assert(type(stateName)=="string", "stateName must be a string")
+  -- states are just regular classes. If superState is nil, this uses Object as superClass
+  local state = class(stateName, superState)
+  self.states[stateName] = state
+  return state
+end
+
+do --create an environment to keep the following variables local
+  local ignoredMethods = {states=1, initialize=1, gotoState=1, addState=1, subclass=1, includes=1, exitState=1, enterState=1}
+  local prevSubclass = StatefulObject.subclass
+  --[[ creates a stateful subclass
+    Subclasses inherit all the states of their superclases, in a special way:
+    If class A has a state called Sleeping and B = A.subClass('B'), then B.states.Sleeping is a subclass of A.states.Sleeping
+    returns the newly created stateful class
+  ]]
+  function StatefulObject:subclass(name)
+    --assert(subclassOf(StatefulObject, self), "Use class:subclass instead of class.subclass")
+    local theClass = prevSubclass(self, name) --for now, theClass is just a regular subclass
+    
+    --the states of the subclass are subclasses of the superclass' states
+    theClass.states = {}
+    for stateName,state in pairs(self.states) do 
+      theClass:addState(stateName, state)
+    end
+
+    --make sure that the currentState is used on the method lookup function before looking on the class dict
+    local classDict = theClass.__classDict
+    classDict.__index = function(instance, method)
+      --first look on the current state
+      local currentState = rawget(instance, 'currentState')
+      if( currentState~=nil and
+          currentState[method]~=nil and
+          ignoredMethods[method]==nil) then
+        return currentState[method]
+      else
+      --if not found, look on the class itself
+        return classDict[method]
+      end
+    end
+
+    return theClass
+  end
+end -- end of the environment to keep ignoredMethods local
+
+--[[ Include override for stateful classes.
+     This is exactly like MiddleClass' include function, except that it module has a property called "states"
+     then each member of that module.states is included on the StatefulObject class.
+     If module.states has a state that doesn't exist on StatefulObject, a new state will be created.
+]]
+function StatefulObject:includes(module)
+  assert(subclassOf(StatefulObject, self), "Use class:includes instead of class.includes")
+  for methodName,method in pairs(module) do
+    if methodName ~="included" and methodName ~= "states" then
+      self[methodName] = method
+    end
+  end
+  if type(module.included)=="function" then module:included(self) end
+  if type(module.states)=="table" then
+    for stateName,moduleState in pairs(module.states) do 
+      local state = self.states[stateName]
+      if(state==nil) then state = theClass:addState(stateName) end
+      state:includes(moduleState)
+    end
+  end
+end