Lua global variable

Global variables do not need to be declared.ProgramIt is very convenient, but when the program is large, a simple spelling mistake may cause bugs and it is difficult to find out. However, we can change this behavior if we like it. Because all the global variables of Lua are stored in a common table, we can use the variables to change the behavior of accessing global variables.

The first method is as follows:

Setretriable (_ g ,{

_ Newindex = function (_, n)

Error ("attempt to write to undeclared variable" .. n, 2)

End,

_ Index = function (_, n)

Error ("attempt to read undeclared variable" .. n, 2)

End,

})

In this way, any attempt to access a non-existent global variable will cause an error:

> A = 1

Stdin: 1: attempt to write to undeclared variable