Question

I’m new to Ruby and I have been trying to get this piece of code to call
MessageBox but can’t. I know I am missing something but I don’t know
what it is. Any help with this would be greatly appreciated!

Here is the code so far:

require 'Win32API'

LoadLibrary = Win32API.new('kernel32','LoadLibrary','P','L')
GetProcAddress = Win32API.new('kernel32','GetProcAddress','LP','L')

Load = LoadLibrary.call('user32.dll')
Proc = GetProcAddress.call(Load,'MessageBox')

Proc.call(0,"Hello World!","MessageBox in Ruby",0)

I know everything is ok except my “Proc.call”. What am I missing?

Answer 1

Is this the error you’re seeing?

undefined method `call' for 0:Fixnum (NoMethodError)

I don’t think it’s necessary to use GetProcAddress for this. Here is some example code for displaying a message box:

require 'Win32API'

msgbox = Win32API.new('user32','MessageBox',['L', 'P', 'P', 'L'], 'I')  
msgbox.call(0, 'Hello World!', 'MessageBox in Ruby', 0)

In your current code Proc is the return value from GetProcAddress and not a callable object. I suspect this is 0 because the call to GetProcAddress has failed.