corona sdk / solar2d multiple moving objects

Question

I have problems with making multiple objects with random movement speed. For example, I need to make 1000 objects and move them with random speed in random direction.

OOP aproach doesn't work, but in love2d it works without any problems.

local displayWidth = display.contentWidth
local displayHeight = display.contentHeight

particle = {}
particle.__index = particle

ActiveParticle = {}

function particle.new()
  instance = setmetatable({}, particle)
  instance.x = math.random(20, displayWidth)
  instance.y = math.random(20, displayHeight)
  instance.xVel = math.random(-150, 150)
  instance.yVel = math.random(-150, 150)
  instance.width = 8
  instance.height = 8
  table.insert(ActiveParticle, instance)
end


function particle:draw()
  display.newRect(self.x, self.y, self.width, self.height)
end

function particle.drawAll()
  for i,instance in ipairs(ActiveParticle) do
    particle:draw()
  end
end

function particle:move()
  self.x = self.x + self.xVel
  self.y = self.y + self.yVel
end

for i = 1, 10 do
  particle.new()
  particle.drawAll()
end

function onUpdate (event)
  instance:move()
end

Runtime:addEventListener("enterFrame", onUpdate)

This code doesn't works, seems solar2d doesn't recognize 'self'.

what do you mean with doen't work? are you facing errors? or how does the expected behaviour differ from the actual one? — Piglet, Apr 15 '21 at 09:06
Yes, i have compilation error. Local instance also doesn't work. Maybe there is different solution to make objects with self parametrs in corona/solora2d? — Exorsky, Apr 15 '21 at 09:17
and don#t you think it would make sense to share that error message with us? — Piglet, Apr 15 '21 at 09:17
main.lua:22 bad argument #1 to 'newRect' (number expected, got nil) stack traceback: [C]: in function 'newRect' main.lua:22 in function 'draw' main.lua:27: in function 'drawAll' main.lua:38: in main chunk — Exorsky, Apr 15 '21 at 09:21

Piglet · Accepted Answer · 2021-04-15T09:29:18.020

function particle.new()
  instance = setmetatable({}, particle)
  instance.x = math.random(20, displayWidth)
  instance.y = math.random(20, displayHeight)
  instance.xVel = math.random(-150, 150)
  instance.yVel = math.random(-150, 150)
  instance.width = 8
  instance.height = 8
  table.insert(ActiveParticle, instance)
end

instance should be local!

Also

function particle.drawAll()
  for i,instance in ipairs(ActiveParticle) do
    particle:draw()
  end
end

Should use instance:draw() as you want to draw the instance not particle. Otherwise self will not refer to instance so you cannot access it's members.

Alternatively use particle.draw(instance)

Due to the __index metamethod instance:draw() will resolve to particle.draw(instance) so inside particle.draw self refers to instance

corona sdk / solar2d multiple moving objects

1 Answers1