Lua Class Inheritance

[Drakkahn]

This doesn't deal so much with Love2D as it deals more with lua. When I call a function from an inhereted "class" I get the error:

Code: Select all

class_base_block.lua:25: attempt to index local 'self' (a nil value)

Traceback

class_base_block.lua:25: in function 'activate'
class_conditional_block.lua:24: in function 'update'
main.lua:83: in function 'update'
[C]: in function 'xpcall'

class_base_block.lua

Code: Select all

base_block =
{

	x=0,
	y=0,
	action=nil							--function of what to do
	
}
base_block.__index=base_block



function base_block:new(variables)

	variables=variables or {}
	local self=setmetatable(variables,self)
	print("A")
	return self

end



function base_block:activate(...)
	return tostring(self.x)

end

class_conditional_block.lua

Code: Select all

conditional_block = base_block:new(
{

	connected={}						--all the blocks connected to this one
	
})
conditional_block.__index=conditional_block



function conditional_block:new(variables)

	variables=variables or {}
	local self=setmetatable(variables,self)
	print("Z")
	return self

end



function conditional_block:update()

	print("ZED: " .. self.activate())

end

[Inny]

This line:

Code: Select all

print("ZED: " .. self.activate())

You want this:

Code: Select all

print("ZED: " .. self:activate())

The colon operator is syntactic sugar, which implies the self variable as the first parameter to the function, seen in Lua 2.5.8 and 2.5.9.

In short, think along these lines:

Code: Select all

-- equivalent declarations
function object:method(parameter) end
object.method = function(self, parameter) end

-- equivalent invocations
object:method(27)
object.method(object, 27)

[Drakkahn]

How can I fix this?

[kikito]

Use : instead of . when you call methods. self:activate() instead of self.activate()