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✓ ANSWER ACCEPTED

How do i call the metamethods in this group of code?

Asked 232 views1 answers
local part = Instance.new("Part",workspace)

local function WrapThisPart(block)
	local properties = {}
	local metamethod = {}
	
	properties.Speed = 20
	properties.Height = 2
	
	metamethod.__index = block
	function metamethod.__newindex(self,index,value)
			properties[index] = value
	end
	return setmetatable(properties,metamethod)
end

local itemWithWrapper = WrapThisPart(part) 




print(itemWithWrapper.Speed)  -- returns 20

print(itemWithWrapper.Weight) -- error

Hi everyone,

Im having trouble trying to call the meta methods on the code above. I can call the values that are already defined in properties, however, the metamethod is not executed when i call a variable that is not defined.

I also dont know how to call the new index function. How would i be able to do that?

Thanks

Anonymous

1 answer

✓ Accepted answer

You can call the new index function if, well, just assign it a value. But make sure you use rawset and rawget instead of table[index]=value and table[index] which causes a C Stack Overflow.

Also note: the difference of metamethod __index and __newindex is whether you want to assign a new value or not.

My example:

local a=setmetatable({},{
	__newindex=function(self,i,v)
		rawset(self,i,v);
	end;
	__index=function(self,i)
		return rawget(self,i)
	end;
});

print(a.Wow) --> Metamethod __index activates here, since we have not assigned an index for table a, it returns nil. Notice how I did not use an =
a.Wow=10-- Metamethod __newindex activates here. Notice how I used an =.
print(a.Wow)--> Metamethod __index activates here once more but this time, since we used rawset to assign the table, it now returns 10
AnonymousPermalink

1 comment

0

Very helpful thank you

Anonymous#

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