Re: Forward declaration of a table and (closure) function

[Ross Berteig <Ross@...>]

At 06:54 PM 7/13/2011, Steve Litt wrote:
> I know the require syntax would definitely work just right if I 
> made
> the definition of Columns and Columns.new() in a separate 
> module, but I
> was trying to find a way to have them in the same file but 
> lower down.

At the time that you attempt to call any function via some 
variable, the function has to be stored in (referenced by, 
actually) that variable.

You cannot write this:

local foo
foo()
function foo() end

but the reason why is clearer if the third line were written in 
its equivalent (syntax sugar free) form:

local foo
foo()
foo = function() end

Now it should be clear that at the time of the attempt to call 
the value in foo, the name is known to be a local variable 
containing nil, but that the assignment of a function to it has 
yet to happen.

The same situation occurs when you attempt to forward declare 
your Columns object and its methods. You can declare that a 
local variable exists named Columns, but until you've stored 
something in it, you shouldn't be surprised that it holds the 
value nil.


Ross Berteig                               Ross@CheshireEng.com
Cheshire Engineering Corp.           http://www.CheshireEng.com/