base class

MoKaLux · August 2019

I would need your help, please.

I don't know how to create a base class for my enemies.

For example I have one enemy class:

Enemy01 = Core.class(Sprite)
 
function Enemy01:init(xname, xposx, xposy)
	-- settings
	self.name = xname
	self.x = xposx
	self.y = xposy
	self.vx = 0
	self.vy = 0
	self.flip = 1
	self.isonfloor = false
	self.isattacking = false
	self.lives = 3
	self.accel = 500
	self.friction = 150
	self.maxspeed = 150
	self.jumpspeed = GRAVITY / 2
end
 
function Enemy01:createAnim(xanimname, xstart, xfinish, xanimslist)
	self.anims[xanimname] = {}
	for i = xstart, xfinish do
		self.anims[xanimname][#self.anims[xanimname] + 1] = xanimslist[i]
	end
end

I have different enemies which would have different parameters value.
How can I make a base class which my enemies would inherit (variables and functions).

I have searched on the forum but I don't know how to handle this.

Thank you in advance for your time.

Apollo14 · August 2019

EnemyAdvanced = Core.class(Enemy01)
 
function EnemyAdvanced:init()
 
end

hgy29 · August 2019

Note that when using Core.class() to create a sub-class, the arguments sent to your new/init function will be used to call the superclass init too, which can have undesired effects. To handle this, I use my own Core.class call:

Core.classArgs=function (p,a)
	local c=Core.class(p)
	c.__new = function(...)
		local b = getmetatable(c)
		local s1 = b.__new(a(...))
		setmetatable(s1, c)
		local init = rawget(c, "init")
		if type(init) == "function" then
			init(s1, ...)
		end
		return s1
	end
	return c
end

It takes a second argument, which is a function that will return the arguments intended for the superclass based on the new class constructor arguments. Example:

-- Define a new class to make a 50x50 pixel. Argument is the plain color	
Pixel50=Core.classArgs(Pixel,function(color) return color,1,50,50 end)
 
--Use it
stage:addChild(Pixel50.new(0xFF0000)) -- Create a 50x50 red pixel

I was thinking about enhancing gideros Core.class to do the same (if second arg is present), what do you think ?

MoKaLux · August 2019

thank you guys for the answers.

@Apollo14 I knew this bit Enemy02 = Core.class(Enemy) but then what do I put in the init()? only the values that are going to change? For example:

Enemy02 = Core.class(Enemy)
function Enemy02:init()
   self.vx = 30
   self:createAnim("walk", 1, 6, myanims_list)
end

Ok, I should experiment more. Right now I do it the "easy" way but I feel like my code isn't nice.

@hgy29 I have read on the forum about Core.class and how it is implemented by @atilim . That is a little bit too advanced for me

so I cannot tell what should be done.

antix · August 2019

With my games I haven't had to create subclasses, I just have a class for enemy which gets passed options that are overwritten on init() to make it different to other enemies. In fact all of my GUI objects use the same method.

Enemy = Core.class(Bitmap)
 
function Enemy:init(texture, options)
  -- default options
  self.position         = {x = 0, y = 0},
  self.velocity         = {x = 0, y = 0},
  self.alive            = true,
  self.type            = 'MUTANT',
  self.canBeClicked     = true
 
  -- copy any supplied options
	if options then
		for key, value in pairs(options) do
			self[key]= value
		end
	end
 
  -- etc, etc
end

Not the greatest code in the world maybe, but it works.

MoKaLux · August 2019

@antix excellent, I am ending up doing something similar, maybe not the best way but it's easier for me! Thank you for sharing.

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