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    Metamethods inheritance

    rrraptorrrraptor Member
    edited July 2020 in General questions
    Is there a way to make this work:
    local Foo = Core.class()
 
function Foo:__call(a, b)
	return a + b
end
 
local Bar = Core.class(Foo)
 
local foo = Foo.new()
local bar = Bar.new()
 
print(foo(10, 20)) --< OK
print(bar(10, 20)) --< error
    Meta function are not inherited?
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    Comments

    • hgy29hgy29 Maintainer
      Accepted Answer
      https://stackoverflow.com/questions/4155842/inheritance-for-metamethods-in-lua
      +1 -1Share on Facebook
    • rrraptorrrraptor Member
      hgy29 said:

      https://stackoverflow.com/questions/4155842/inheritance-for-metamethods-in-lua

      Didn't help much :smile:

      I came up with another solution. Not the best, but it works :)
      local Foo = Core.class()
--
function Foo:postInit()	
	local mt = getmetatable(self)
	mt.__call = function(self, a, b)
		return "base call", a + b
	end
	setmetatable(self, mt)
end
 
local Bar = Core.class(Foo)
 
function Bar:postInit()	
	local mt = getmetatable(self)
	mt.__call = function(self, a, b)
		return "overridden", a * b
	end
	setmetatable(self, mt)
end
 
local foo = Foo.new()
local bar = Bar.new()
 
print(foo(10, 20)) --< 30
print(bar(10, 20)) --< 200
      SuperShape | Nice blured shapes with shadows | Simple button pad | Simple layer class | Simple UI library | 2D camera lib | Color picker | FPS graph | Dear ImGui | cute_c2
      +1 -1Share on Facebook
    • rrraptorrrraptor Member
      edited July 2020
      Better solution:
      -- since I have custom methods that starts from "__" I need to reject them
local metamethods = { "__add","__call","__concat","__div","__le","__lt","__mod","__mul","__pow","__sub","__tostring","__unm" } 
 
local Foo = Core.class()
 
function Foo:postInit()
	local mt = getmetatable(self)
	for _,k in ipairs(metamethods) do
		if (not rawget(self,k) and self[k]) then
			mt[k] = self[k]
		end
	end
end
 
function Foo:__call(a, b)
	return a + b
end
 
local Bar = Core.class(Foo)
 
--[[ can be overridden
function Bar:__call(a, b)
	return a * b
end
--]]
 
local foo = Foo.new()
local bar = Bar.new()
 
print(foo(10, 20)) --< 30
print(bar(10, 10)) --< 20
      SuperShape | Nice blured shapes with shadows | Simple button pad | Simple layer class | Simple UI library | 2D camera lib | Color picker | FPS graph | Dear ImGui | cute_c2
      +1 -1Share on Facebook
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