Lua: strange behavior with loadstring?

Question

I am using loadstring with Lua 5.1:

Main

function Object:load_string(str)
    loadstring(str)() -- self in this is 'nil'
    print(self) -- self here is a 'table'
end
obj:load_string('print(self)')

Output

> nil
> table: 1557C890

Why is it that the self used in loadstring resolves to a nil value when the self variable is accessible in the function and can be printed directly?

Answer 1

Code contained in string (or file) is not related to current scope in any way. loadstring() creates new anonymous vararg function. You must pass self explicitly.

function Object:load_string(str)
    loadstring(str)(self) -- pass self explicitly
    print(self) -- self here is a 'table'
end

obj:load_string('local self = ...; print(self)')

Answer 2

Most probably, the code in str contains a reference to self as a global variable . The self in load_string is a local variable, not accessible to the code in str .