Programming Ruby: The Pragmatic Programmer's Guide

# Programming Ruby ### The Pragmatic Programmer's Guide
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# Microsoft Windows Support

The three libraries documented in this chapter turn Ruby into a powerful and convenient Windows scripting language. Now you have the power to control your applications, but in a controlled, object-oriented environment.

class WIN32OLE |
Parent: | Object
Version: | 1.6

### Index:

connect const_load new [ ] [ ]= each invoke

    require 'win32ole'
    ie = WIN32OLE.new('InternetExplorer.Application')
    ie.visible = true
    ie.gohome

`WIN32OLE` provides a client interface to Windows 32 OLE Automation servers. See the tutorial description on page 164 for more information.

constants

`WIN32OLE::VERSION` |  | Current version number

class methods
connect | WIN32OLE.connect( aString ) -> wapi
|  | Returns a new OLE automation client connected to an existing instance of the named automation server.
const_load | WIN32OLE.const_load( wapi, [ aClass=WIN32OLE ] ) -> `nil`
|  | Defines the constants from the specified automation server as class constants in aClass.
new | WIN32OLE.new( aString ) -> wapi
|  | Returns a new OLE automation client connected to a new instance of the automation server named by aString.

instance methods
[ ] | wapi[ aString ] -> anObject
|  | Returns the named property from the OLE automation object.
[ ]= | wapi[ aString ] = aValue -> `nil`
|  | Sets the named property in the OLE automation object.
each | wapi.each {| anObj | block } -> `nil`
|  | Iterates over each item of this OLE server that supports the `IEnumVARIANT` interface.
invoke | wapi.invoke ( aCmdString, [ args ]* ) -> anObject
|  | Invokes the command given in aCmdString with the given args. args may be a `Hash` of named parameters and values. You don't need to call `invoke` explicitly; this class uses `method_missing` to forward calls through `invoke`, so you can simply use the OLE methods as methods of this class.

class WIN32OLE_EVENT |
Parent: | Object
Version: | 1.6

### Index:

message_loop new on_event

This (slightly modified) example from the Win32OLE 0.1.1 distribution shows the use of an event sink.

    require 'win32ole'

    $urls = []

    def navigate(url)
      $urls << url
    end

    def stop_msg_loop
      puts "IE has exited..."
      throw :done
    end

    def default_handler(event, *args)
      case event
      when "BeforeNavigate"
        puts "Now Navigating to #{args[0]}..."
      end
    end

    ie = WIN32OLE.new('InternetExplorer.Application')
    ie.visible = TRUE
    ie.gohome
    ev = WIN32OLE_EVENT.new(ie, 'DWebBrowserEvents')

    ev.on_event {|*args| default_handler(*args)}
    ev.on_event("NavigateComplete") {|url| navigate(url)}
    ev.on_event("Quit") {|*args| stop_msg_loop}

    catch(:done) {
      loop {
        WIN32OLE_EVENT.message_loop
      }
    }

    puts "You Navigated to the following URLs: "
    $urls.each_with_index do |url, i|
      puts "(#{i+1}) #{url}"
    end

`WIN32OLE_EVENT` is used in conjunction with the `WIN32OLE` class to add callbacks for Windows 32 events.

class methods
message_loop | WIN32OLE_EVENT.message_loop -> `nil`
|  | Executes the Windows event loop, translating and dispatching events.
new | WIN32OLE_EVENT.new ( anOle, aName ) -> wapi
|  | Returns a new `WIN32OLE_EVENT` (an event sink) for the given `WIN32OLE` object and named event source. If aName is `nil`, it will attempt to use the default source and will raise a `RuntimeError` if it cannot find one.

instance methods
on_event | wapi.on_event ( [ anEvent ] ) {| args | block } -> `nil`
|  | Defines a callback for the named anEvent. If anEvent is `nil`, then this callback is associated with all events. The block will be given any arguments appropriate for this event.

class Win32API |
Parent: | Object
Version: | 1.6

### Index:

new call Call

This example is from the Ruby distribution, in `ext/Win32API`:

    require 'Win32API'

    getCursorPos = Win32API.new("user32", "GetCursorPos", ['P'], 'V')

    lpPoint = " " * 8 # store two LONGs
    getCursorPos.Call(lpPoint)
    x, y = lpPoint.unpack("LL") # get the actual values

    print "x: ", x, "\n"
    print "y: ", y, "\n"

    ods = Win32API.new("kernel32", "OutputDebugString", ['P'], 'V')
    ods.Call("Hello, World\n")

    GetDesktopWindow = Win32API.new("user32", "GetDesktopWindow", [], 'L')
    GetActiveWindow = Win32API.new("user32", "GetActiveWindow", [], 'L')
    SendMessage = Win32API.new("user32", "SendMessage", ['L'] * 4, 'L')
    SendMessage.Call(GetDesktopWindow.Call, 274, 0xf140, 0)

The `Win32API` module allows access to any arbitrary Windows 32 function. Many of these functions take or return a `Pointer` datatype---a region of memory corresponding to a C string or structure type.

In Ruby, these pointers are represented using class `String`, which contains a sequence of 8-bit bytes. It is up to you to pack and unpack the bits in the `String`. See the reference section for unpack on page 378 and pack on page 286 for details.

class methods
new | Win32API.new( dllname, procname, importArray, export ) -> wapi
|  | Returns a new object representing a Windows 32 API function. dllname is the name of the DLL containing the function, such as ``user32'' or ``kernel32.'' procname is the name of the desired function. importArray is an array of strings representing the types of arguments to the function. export is a string representing the return type of the function. Strings ``n'' and ``l'' represent numbers, ``i'' represent integers, ``p'' represents pointers to data stored in a string, and ``v'' represents a void type (used for export parameters only). These strings are case-insensitive.

instance methods
call | wapi.call( [ args ]* ) -> anObject
|  | Calls this API function with the given arguments, which must match the signature specified to `new`.
Call | wapi.Call( [ args ]* ) -> anObject
|  | Synonym for `Win32API#call`.

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Extracted from the book "Programming Ruby - The Pragmatic Programmer's Guide"
Copyright © 2001 by Addison Wesley Longman, Inc. This material may be distributed only subject to the terms and conditions set forth in the Open Publication License, v1.0 or later (the latest version is presently available at http://www.opencontent.org/openpub/)).

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