base/ObjectList.lua

   1 --[[
   2   ObjectList class
   3   ----------------
   4
   5   This class is designed to provide a better way to manage objects than
   6   the (now deprecated) resource_manager. The iterator provided is
   7   particularly useful.
   8
   9     Functions of ObjectList:
  10     ------------------------
  11       new(o)            --- constructor
  12       push_front(obj)   --- adds an object to the front of the list
  13       push_back(obj)    --- adds an object to the back of the list
  14       front()           --- returns the element at the front of the
  15                             list, else nil
  16       back()            --- returns the element at the back of the
  17                             list, else nil
  18       pop_front()       --- removes the front element from the list
  19       pop_back()        --- removes the back element from the list
  20       clear()           --- clears the list
  21       iterator()        --- returns an iterator for use in a generic
  22                             for loop
  23       update_all(delta) --- updates all Object instances in the list, delta is optional
  24       draw_all()        --- draws all Object instances in the list
  25 --]]
  26
  27
  28 --object list node
  29
  30 ObjectListNode = {}
  31 ObjectListNode.data = nil
  32 ObjectListNode.next = nil
  33
  34 --constructor
  35 function ObjectListNode:new(o)
  36   o = o or {}
  37   setmetatable(o, self)
  38   self.__index = self
  39   return o
  40 end
  41
  42
  43 --object list
  44 ObjectList = {}
  45 ObjectList.head = nil
  46 ObjectList.tail = nil
  47 ObjectList.temp = nil
  48 ObjectList.size = 0
  49
  50 --constructor
  51 function ObjectList:new(o)
  52   o = o or {}
  53   setmetatable(o, self)
  54   self.__index = self
  55   return o
  56 end
  57
  58 --adds an object to the front of the list
  59 function ObjectList:push_front(obj)
  60   if self.head == nil then
  61     self.head = ObjectListNode:new()
  62     self.tail = self.head
  63     self.head.data = obj
  64   else
  65     self.temp = ObjectListNode:new()
  66     self.temp.data = obj
  67     self.temp.next = self.head
  68     self.head = self.temp
  69     self.temp = nil
  70   end
  71   self.size = self.size + 1
  72 end
  73
  74 --adds an object to the back of the list
  75 function ObjectList:push_back(obj)
  76   if self.head == nil then
  77     self.head = ObjectListNode:new()
  78     self.tail = self.head
  79     self.head.data = obj
  80   else
  81     self.temp = ObjectListNode:new()
  82     self.temp.data = obj
  83     self.tail.next = self.temp
  84     self.tail = self.temp
  85     self.temp = nil
  86   end
  87   self.size = self.size + 1
  88 end
  89
  90 --returns the first element in the list (so it can be used like a stack)
  91 function ObjectList:front()
  92   if self.head ~= nil then
  93     return self.head.data
  94   else
  95     return nil
  96   end
  97 end
  98
  99 --returns the last element in the list
 100 function ObjectList:back()
 101   if self.head ~= nil then
 102     return self.tail.data
 103   else
 104     return nil
 105   end
 106 end
 107
 108 --removes the first element
 109 function ObjectList:pop_front()
 110   if self.head ~= nil then
 111     self.head = self.head.next
 112     self.size = self.size - 1
 113   end
 114 end
 115
 116 --removes the last element
 117 function ObjectList:pop_back()
 118   if self.head ~= nil then
 119     self.temp = self.head
 120     while self.temp.next.next ~= nil do
 121       self.temp = self.temp.next
 122     end
 123     self.tail = self.temp
 124     self.temp.next = nil
 125     self.size = self.size - 1
 126     self.temp = nil
 127   end
 128 end
 129
 130 --clears the list
 131 function ObjectList:clear()
 132   self.head = nil
 133   self.tail = nil
 134   self.temp = nil
 135   self.size = 0
 136 end
 137
 138 --iterator for traversing the list
 139 function ObjectList:iterator()
 140   local i, r
 141   return function ()
 142     if i == nil and r ~= true then
 143       i = ObjectListNode:new()
 144       i.next = self.head
 145       r = true
 146     end
 147     i = i.next
 148     if i then
 149       return i.data
 150     else
 151       return nil
 152     end
 153   end
 154 end
 155
 156 --runs the update function of each Object contained within,
 157 -- collecting any Objects that need to be collected
 158 function ObjectList:update_all(delta)
 159   if self.head and self.head.data and self.head.data.collect == true then
 160     self.head = self.head.next
 161     self.size = self.size - 1
 162   end
 163
 164   self.temp = self.head
 165   while self.temp do
 166     if self.temp.next and self.temp.next.data and self.temp.next.data.collect == true then
 167       self.temp.next.data = nil
 168       self.temp.next = self.temp.next.next
 169       self.size = self.size - 1
 170     end
 171     if self.temp.data.update then self.temp.data:update(delta) end
 172     self.temp = self.temp.next
 173   end
 174 end
 175
 176 --calls draw on all of the Objects in the list
 177 function ObjectList:draw_all()
 178   for obj in self:iterator() do
 179     if obj.draw then obj:draw() end
 180   end
 181 end
 182
 183 --looks to see if an object exists already in the list
 184 function ObjectList:exists(o)
 185   for obj in self:iterator() do
 186     if obj == o then return true end
 187   end
 188   return false
 189 end