Game Objects as Lua Tables

In the first part, several game objects have been introduced. They have been represented as Lua tables in the code, but some improvements are possible.

In complicated games a number of game elements can be wast and it is sometimes convenient to use object-oriented approach in the code to organize and structure them. In such a case, each game object is represented as an instance of a class. For simple games, such as this one, it is not necessary, and it is suffice to use basic Lua functionality and represent each game object as a simple Lua table. An example of object-oriented approach is provided in one of the appendices.

Regarding the initial code, a first thing to notice is that love.update and love.draw can be split into several functions, corresponding to update and draw of independent game objects:

function love.update( dt )
   ball.update( dt )
   platform.update( dt )
   .....
end
 
function love.draw()
   ball.draw()
   platform.draw()
   .....
end

The ball.update and ball.draw are defined as

function ball.update( dt )
   ball.position_x = ball.position_x + ball.speed_x * dt
   ball.position_y = ball.position_y + ball.speed_y * dt   
end

function ball.draw()
   local segments_in_circle = 16
   love.graphics.circle( 'line',
                         ball.position_x,
                         ball.position_y,
                         ball.radius,
                         segments_in_circle )   
end

The functions for the platform are similar.

With bricks, however, the situation is more complicated. First of all, there are going to be several of them, each with it's own characteristics. I replace the brick table from the previous part with a different one - bricks, where I'm going to store all the relevant information.

local bricks = {}
.....

The bricks themselves are going to be stored in the bricks.current_level_bricks table, which will be populated on level construction.

bricks.current_level_bricks = {}

Each single brick is represented as a table with position_x, position_y, width and height fields. I define a special function bricks.new_brick to construct such objects:

function bricks.new_brick( position_x, position_y, width, height )
   return( { position_x = position_x,
             position_y = position_y,
             width = width or bricks.brick_width,           --(*1)
             height = height or bricks.brick_height } )
end

(*1): If width is supplied as an argument to the bricks.new_brick call, than that value is used; otherwise the default one bricks.brick_width is used.

Each single brick can be drawn with the following function:

function bricks.draw_brick( single_brick )
   love.graphics.rectangle( 'line',
                            single_brick.position_x,
                            single_brick.position_y,
                            single_brick.width,
                            single_brick.height )   
end

As before, there is nothing to update in brick:

function bricks.update_brick( single_brick )   
end