Tuto tiny-ecs demo Part 7 Systems to move actors
We continue with our tiny-ecs demo. It is time to add some action!
A System to control our player1
We will create a system to control our player1 using the keyboard.
In the systems folder "_S", create a file called "sPlayer1Control.lua" for example and copy the following code:
SPlayer1Control = Core.class()
function SPlayer1Control:init(xtiny) -- tiny function
xtiny.system(self) -- called only once on init (no update)
end
function SPlayer1Control:filter(ent) -- tiny function
return ent.isplayer1
end
function SPlayer1Control:onAdd(ent) -- tiny function
stage:addEventListener(Event.KEY_DOWN, function(e) -- is the stage best?
if e.keyCode == KeyCode.LEFT then ent.isleft = true end
if e.keyCode == KeyCode.RIGHT then ent.isright = true end
if e.keyCode == KeyCode.SPACE then ent.isaction1 = true end
end)
stage:addEventListener(Event.KEY_UP, function(e) -- is the stage best?
if e.keyCode == KeyCode.LEFT then ent.isleft = false end
if e.keyCode == KeyCode.RIGHT then ent.isright = false end
if e.keyCode == KeyCode.SPACE then ent.isaction1 = false end
end)
end
In the init function we tell tiny-ecs that this system will be executed only once on init.
Then in the filter function we tell tiny-ecs to execute the system on entities with an id of isplayer1 only.
Finally, in the onAdd function, we add two event listeners, one for the key down event, and one for the key up event. You can choose your key binding here, or even add event listeners for a joypad, mouse, ...
And a System to move our actors
Now we add another system which will be responsible for moving the actors (entities).
In the same systems folder "_S", create a file called sDynamicBodies.lua for example, and copy the following code:
SDynamicBodies = Core.class()
function SDynamicBodies:init(xtiny) -- tiny function
self.tiny = xtiny -- ref so we can remove entities from tiny system
self.tiny.processingSystem(self) -- called once on init and every update
end
function SDynamicBodies:filter(ent) -- tiny function
return ent.isactor and ent.body -- only actors with body component
end
function SDynamicBodies:onAdd(ent) -- tiny function
end
function SDynamicBodies:onRemove(ent) -- tiny function
end
function SDynamicBodies:process(ent, dt) -- tiny function
-- velocity
if ent.isleft and not ent.isright then -- LEFT
ent.body.vx = -ent.body.speed
elseif ent.isright and not ent.isleft then -- RIGHT
ent.body.vx = ent.body.speed
else
ent.body.vx = 0
end
-- move
ent.x += ent.body.vx * dt
ent.sprite:setPosition(ent.x, ent.y)
end
All systems follow the same pattern, they are easy to create!
Here, in the init function, we create a reference to the xtiny parameter, so we can use it later to add or remove actors from tiny-ecs world.
Then, we tell tiny-ecs that this system needs to be updated each game loop (cf: Tuto_tiny-ecs_demo_Part_3_tiny-ecs_World, self.tiny.world:update(dt)).
In the filter function, we tell tiny-ecs that this system applies to entities with an id of isactor and body (remember that a component can serve as an id).
Finally, in the process function, we check if an actor is going left or right to add velocity to its body. The velocity will change the actor position.
World addSystem
Last, we add our new systems to tiny-ecs world.
Please go to the "LevelX.lua" file and complete the code as follow:
...
-- the player (xspritelayer, x, y)
self.player1 = EPlayer1.new(self.camera, 12*16, 10*16)
self.tiny.world:addEntity(self.player1)
-- add systems to tiny-ecs
self.tiny.world:add(
SDrawable.new(self.tiny),
SDynamicBodies.new(self.tiny),
SPlayer1Control.new(self.tiny)
)
...
I am not sure if the order systems are added is important! Make sure to put them in an order that speaks to you and your team :-)
That's it, you can run the demo and you should be able to control the player1 with the keyboard.
Next?
In the next part, we add some more actors, they will be enemies.
Prev.: Tuto tiny-ecs demo Part 6 tiny-ecs Component
Next: Tuto tiny-ecs demo Part 8 Enemies
