base/Object.lua

   1 --the Object class
   2 --all objects should descend from this
   3
   4 Object = {}
   5 Object.x = 0
   6 Object.y = 0
   7 Object.w = 0
   8 Object.h = 0
   9
  10 Object.x_offset = 0
  11 Object.y_offset = 0
  12
  13 --movement
  14 Object.heading = 0  --heading in degrees
  15 Object.speed = 0  --speed in pixels
  16
  17 --rotation
  18 Object.rotation = 0
  19 Object.angular_velocity = 0
  20
  21 Object.image = nil --this should hold the image of the Object
  22 Object.rects = ObjectList:new() --this field should hold the collision Rect objects
  23
  24 Object.type = "Object" --for each class, this should be set to a unique identifier. it is used in collision detection
  25
  26 Object.max_updates = -1 --if set to a non-negative, non-zero number, object will automatically collect itself after this many updates
  27 Object.num_updates = 0 --current count of updates
  28
  29 Object.no_collide = false --setting this to true will prevent it from colliding
  30 Object.collect = false  --set to true to cause resource manager to collect this object
  31
  32 function Object:new(o)
  33   o = o or {}
  34   setmetatable(o, self)
  35   self.__index = self
  36   return o
  37 end
  38
  39 --updates the object's state
  40 function Object:update(delta)
  41   if delta ~= nil then
  42     delta = delta/1000
  43   end
  44
  45   self.x = self.x + math.cos(math.rad(self.heading)) * (self.speed * (delta or 1))
  46   self.y = self.y + math.sin(math.rad(-1 * self.heading)) * (self.speed * (delta or 1))
  47   self.rotation = (self.rotation + (self.angular_velocity * (delta or 1))) % 360
  48
  49   --Object self-collect check (mostly for particle systems)
  50   if self.max_updates > 0 then
  51     self.num_updates = self.num_updates + 1
  52     if self.num_updates >= self.max_updates then
  53       self.collect = true
  54     end
  55   end
  56
  57 end
  58
  59 --default draw routine
  60 function Object:draw()
  61   display(self.image, self.x-self.x_offset, self.y-self.y_offset, self.rotation, 1, 1)
  62 end
  63
  64 --there is no predefined collision behavior
  65 -- "ids" is the list of Rect ids that have been collided with
  66 -- "object" is the Object that is colliding with this one
  67 function Object:collide(ids, object)
  68
  69 end
  70
  71 --returns the coordinate of the center
  72 function Object:get_center()
  73   return math.floor(self.x + (self.w/2)), math.floor(self.y + (self.h/2))
  74 end
  75
  76 --sets the drawing offset of the sprite
  77 function Object:set_origin(x,y)
  78   self.x_offset = x
  79   self.y_offset = y
  80 end
  81
  82 --unloads resources and nils out the class' table
  83 --  There is no defined behavior for this function in the Object class.
  84 function Object:unload()
  85         --normally, resources would be unloaded here
  86         --and one would put a line such as
  87         --ClassName = nil at the end
  88 end