notanimposter/inheritance.lua

##inheritance.lua

Improved by notanimposter

based on http://lua-users.org/wiki/InheritanceTutorial

---

Do this bit at the top:

class = require "inheritance"

Now you have a few different ways you can make a class:

• you can call 'class' with a table containing the static members:

  local Thing = class {
  	create = function(self, v)
  		self.value = 16
          --does not need to return anything
  	end,
  	doSomething = function(self)
  		return "boop "..tostring(self.class)
  	end
  }

• or with a function that defines the static members. In this context, you can use This to refer to the class. Note that you need ()s if you want to pass a function:

  local Thing = class(function()
  	--use 'This' to refer to the class in this context
  	function This:create()
  		self.value = 16
  	end
  	function This:doSomething()
  		return "boop "..tostring(self.class)
  	end
  end)

When you want to extend a class, you also have a few options:

• you can use the + operator:

  local NewThing = Thing + {
  }

• which is really just shorthand for:

  local NewThing = Thing:extend {
  }

• you can also use functions instead of tables in those scenarios, but you get the idea.

To make a new instance, just do:

local nt = NewThing(args)

Don't call Thing:create(). Thing() maps to a wrapper function that calls Thing:create() for you so you don't need to return self at the end of all your create() functions.

Every class/instance has these:

• nt.class: the class object of the instance nt
• nt.super: the parent class object
• nt < Thing or Thing > nt tests whether nt inherits from Thing, which is just shorthand for nt:isa(Thing)