Lua How to create custom function that can be used on variables follow up

Question

Following up with my previous question (link here: Lua How to create custom function that can be used on variables?), is there a way to create the same kind of function that works for other things other than tables? For example,

str = "stuff"
letter = str:foo() --Maybe have the foo function extract the first letter?

Is there a way to create a function that works in the same way that

lowerCasestr = str:lower()

works?

Yu Hao · Accepted Answer · 2015-01-31 03:00:11Z

7

All strings share the same metatable, add your custom function to its __index table:

function first_letter(str)
  return str:sub(1, 1)
end

local mt = getmetatable("")
mt.__index["first_letter"] = first_letter

local str = "stuff"
print(str:first_letter())

answered Jan 31, 2015 at 3:00

Yu Hao

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1 Comment

Lee Yi Over a year ago

What about objects like files? Do they have separate metatables as well? For the matter, do all types of objects in Lua have metatables?

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