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-=pod
-
-=head1 NAME
-
-The Perl Journal #10 - Win32::OLE by Jan Dubois
-
-=head1 INTRODUCTION
-
-Suppose you're composing a document with Microsoft Word. You want to
-include an Excel spreadsheet. You could save the spreadsheet in some
-image format that Word can understand, and import it into your
-document. But if the spreadsheet changes, your document will be out of
-date.
-
-Microsoft's OLE (Object Linking and Embedding, pronounced "olay") lets
-one program use objects from another. In the above scenario, the
-spreadsheet is the object. As long as Excel makes that spreadsheet
-available as an OLE object, and Word knows to treat it like one, your
-document will always be current.
-
-You can control OLE objects from Perl with the Win32::OLE module, and
-that's what this article is about. First, I'll show you how to "think
-OLE," which mostly involves a lot of jargon. Next, I'll show you the
-mechanics involved in using Win32::OLE. Then we'll go through a Perl
-program that uses OLE to manipulate Microsoft Excel, Microsoft Access,
-and Lotus Notes. Finally, I'll talk about Variants, an internal OLE
-data type.
-
-
-=head1 THE OLE MINDSET
-
-When an application makes an OLE object available for other
-applications to use, that's called OLE I<automation>. The program
-using the object is called the I<controller>, and the application
-providing the object is called the I<server>. OLE automation is guided
-by the OLE Component Object Model (COM) which specifies how those
-objects must behave if they are to be used by other processes and
-machines.
-
-There are two different types of OLE automation servers. I<In-process>
-servers are implemented as dynamic link libraries (DLLs) and run in
-the same process space as the controller. I<Out-of-process> servers
-are more interesting; they are standalone executables that exist as
-separate processes - possibly on a different computer.
-
-The Win32::OLE module lets your Perl program act as an OLE
-controller. It allows Perl to be used in place of other languages like
-Visual Basic or Java to control OLE objects. This makes all OLE
-automation servers immediately available as Perl modules.
-
-Don't confuse ActiveState OLE with Win32::OLE. ActiveState OLE is
-completely different, although future builds of ActiveState Perl (500
-and up) will work with Win32::OLE.
-
-Objects can expose OLE methods, properties, and events to the outside
-world. Methods are functions that the controller can call to make the
-object do something; properties describe the state of the object; and
-events let the controller know about external events affecting the
-object, such as the user clicking on a button. Since events involve
-asynchronous communication with their objects, they require either
-threads or an event loop. They are not yet supported by the Win32::OLE
-module, and for the same reason ActiveX controls (OCXs) are currently
-unsupported as well.
-
-=head1 WORKING WITH WIN32::OLE
-
-The Win32::OLE module doesn't let your Perl program create OLE
-objects. What it does do is let your Perl program act like a remote
-control for other applications-it lets your program be an OLE
-controller. You can take an OLE object from another application
-(Access, Notes, Excel, or anything else that speaks OLE) and invoke
-its methods or manipulate its properties.
-
-=head2 THE FIRST STEP: CREATING AN OLE SERVER OBJECT
-
-First, we need to create a Perl object to represent the OLE
-server. This is a weird idea; what it amounts to is that if we want to
-control OLE objects produced by, say, Excel, we have to create a Perl
-object that represents Excel. So even though our program is an OLE
-controller, it'll contain objects that represent OLE servers.
-
-You can create a new OLE I<server object> with C<< Win32::OLE->new >>.
-This takes a program ID (a human readable string like
-C<'Speech.VoiceText'>) and returns a server object:
-
- my $server = Win32::OLE->new('Excel.Application', 'Quit');
-
-Some server objects (particularly those for Microsoft Office
-applications) don't automatically terminate when your program no
-longer needs them. They need some kind of Quit method, and that's just
-what our second argument is. It can be either a code reference or a
-method name to be invoked when the object is destroyed. This lets you
-ensure that objects will be properly cleaned up even when the Perl
-program dies abnormally.
-
-To access a server object on a different computer, replace the first
-argument with a reference to a list of the server name and program ID:
-
- my $server = Win32::OLE->new(['foo.bar.com',
- 'Excel.Application']);
-
-(To get the requisite permissions, you'll need to configure your
-security settings with F<DCOMCNFG.EXE>.)
-
-You can also directly attach your program to an already running OLE
-server:
-
- my $server = Win32::OLE->GetActiveObject('Excel.Application');
-
-This fails (returning C<undef>) if no server exists, or if the server
-refuses the connection for some reason. It is also possible to use a
-persistent object moniker (usually a filename) to start the associated
-server and load the object into memory:
-
- my $doc = Win32::OLE->GetObject("MyDocument.Doc");
-
-=head2 METHOD CALLS
-
-Once you've created one of these server objects, you need to call its
-methods to make the OLE objects sing and dance. OLE methods are
-invoked just like normal Perl object methods:
-
- $server->Foo(@Arguments);
-
-This is a Perl method call - but it also triggers an OLE method call
-in the object. After your program executes this statement, the
-C<$server> object will execute its Foo() method. The available methods
-are typically documented in the application's I<object model>.
-
-B<Parameters.> By default, all parameters are positional
-(e.g. C<foo($first, $second, $third)>) rather than named (e.g.
-C<< foo(-name => "Yogi", -title => "Coach") >>). The required parameters
-come first, followed by the optional parameters; if you need to
-provide a dummy value for an optional parameter, use undef.
-
-Positional parameters get cumbersome if a method takes a lot of
-them. You can use named arguments instead if you go to a little extra
-trouble - when the last argument is a reference to a hash, the
-key/value pairs of the hash are treated as named parameters:
-
- $server->Foo($Pos1, $Pos2, {Name1 => $Value1,
- Name2 => $Value2});
-
-B<Foreign Languages and Default Methods.> Sometimes OLE servers use
-method and property names that are specific to a non-English
-locale. That means they might have non-ASCII characters, which aren't
-allowed in Perl variable names. In German, you might see C<Öffnen> used
-instead of C<Open>. In these cases, you can use the Invoke() method:
-
- $server->Invoke('Öffnen', @Arguments);
-
-This is necessary because C<< $Server->Öffnen(@Arguments) >> is a syntax
-error in current versions of Perl.
-
-=head2 PROPERTIES
-
-As I said earlier, objects can expose three things to the outside
-world: methods, properties, and events. We've covered methods, and
-Win32::OLE can't handle events. That leaves properties. But as it
-turns out, properties and events are largely interchangeable. Most
-methods have corresponding properties, and vice versa.
-
-An object's properties can be accessed with a hash reference:
-
- $server->{Bar} = $value;
- $value = $server->{Bar};
-
-This example sets and queries the value of the property named
-C<Bar>. You could also have called the object's Bar() method to
-achieve the same effect:
-
- $value = $server->Bar;
-
-However, you can't write the first line as C<< $server->Bar = $value >>,
-because you can't assign to the return value of a method call. In
-Visual Basic, OLE automation distinguishes between assigning the name
-of an object and assigning its value:
-
- Set Object = OtherObject
-
- Let Value = Object
-
-The C<Set> statement shown here makes C<Object> refer to the same object as
-C<OtherObject>. The C<Let> statement copies the value instead. (The value of
-an OLE object is what you get when you call the object's default
-method.
-
-In Perl, saying C<< $server1 = $server2 >> always creates another reference,
-just like the C<Set> in Visual Basic. If you want to assign the value
-instead, use the valof() function:
-
- my $value = valof $server;
-
-This is equivalent to
-
- my $value = $server->Invoke('');
-
-=head2 SAMPLE APPLICATION
-
-Let's look at how all of this might be used. In Listing: 1 you'll see
-F<T-Bond.pl>, a program that uses Win32::OLE for an almost-real world
-application.
-
-The developer of this application, Mary Lynch, is a financial futures
-broker. Every afternoon, she connects to the Chicago Board of Trade
-(CBoT) web site at http://www.cbot.com and collects the time and sales
-information for U.S. T-bond futures. She wants her program to create a
-chart that depicts the data in 15-minute intervals, and then she wants
-to record the data in a database for later analysis. Then she wants
-her program to send mail to her clients.
-
-Mary's program will use Microsoft Access as a database, Microsoft
-Excel to produce the chart, and Lotus Notes to send the mail. It will
-all be controlled from a single Perl program using OLE automation. In
-this section, we'll go through T-Bond. pl step by step so you can see
-how Win32::OLE lets you control these applications.
-
-=head2 DOWNLOADING A WEB PAGE WITH LWP
-
-However, Mary first needs to amass the raw T-bond data by having her
-Perl program automatically download and parse a web page. That's the
-perfect job for LWP, the libwww-perl bundle available on the CPAN. LWP
-has nothing to do with OLE. But this is a real-world application, and
-it's just what Mary needs to download her data from the Chicago Board
-of Trade.
-
- use LWP::Simple;
- my $URL = 'http://www.cbot.com/mplex/quotes/tsfut';
- my $text = get("$URL/tsf$Contract.htm");
-
-She could also have used the Win32::Internet module:
-
- use Win32::Internet;
- my $URL = 'http://www.cbot.com/mplex/quotes/tsfut';
- my $text = $Win32::Internet->new->FetchURL("$URL/tsf$Contract.htm");
-
-Mary wants to condense the ticker data into 15 minute bars. She's
-interested only in lines that look like this:
-
- 03/12/1998 US 98Mar 12116 15:28:34 Open
-
-A regular expression can be used to determine whether a line looks
-like this. If it does, the regex can split it up into individual
-fields. The price quoted above, C<12116>, really means 121 16/32, and
-needs to be converted to 121.5. The data is then condensed into 15
-minute intervals and only the first, last, highest, and lowest price
-during each interval are kept. The time series is stored in the array
-C<@Bars>. Each entry in C<@Bars> is a reference to a list of 5 elements:
-Time, Open, High, Low, and Close.
-
- foreach (split "\n", $text) {
- # 03/12/1998 US 98Mar 12116 15:28:34 Open
- my ($Date,$Price,$Hour,$Min,$Sec,$Ind) =
- m|^\s*(\d+/\d+/\d+) # " 03/12/1998"
- \s+US\s+\S+\s+(\d+) # " US 98Mar 12116"
- \s+(\d+):(\d+):(\d+) # " 12:42:40"
- \s*(.*)$|x; # " Ask"
- next unless defined $Date;
- $Day = $Date;
-
- # Convert from fractional to decimal format
- $Price = int($Price/100) + ($Price%100)/32;
-
- # Round up time to next multiple of 15 minutes
- my $NewTime = int(($Sec+$Min*60+$Hour*3600)/900+1)*900;
- unless (defined $Time && $NewTime == $Time) {
- push @Bars, [$hhmm, $Open, $High, $Low, $Close]
- if defined $Time;
- $Open = $High = $Low = $Close = undef;
- $Time = $NewTime;
- my $Hour = int($Time/3600);
- $hhmm = sprintf "%02d:%02d", $Hour, $Time/60-$Hour*60;
- }
-
- # Update 15 minute bar values
- $Close = $Price;
- $Open = $Price unless defined $Open;
- $High = $Price unless defined $High && $High > $Price;
- $Low = $Price unless defined $Low && $Low > $Price;
- }
-
- die "No data found" unless defined $Time;
- push @Bars, [$hhmm, $Open, $High, $Low, $Close];
-
-=head2 MICROSOFT ACCESS
-
-Now that Mary has her T-bond quotes, she's ready to use Win32::OLE to
-store them into a Microsoft Access database. This has the advantage
-that she can copy the database to her lap-top and work with it on her
-long New York commute. She's able to create an Access database as
-follows:
-
- use Win32::ODBC;
- use Win32::OLE;
-
- # Include the constants for the Microsoft Access
- # "Data Access Object".
-
- use Win32::OLE::Const 'Microsoft DAO';
-
- my $DSN = 'T-Bonds';
- my $Driver = 'Microsoft Access Driver (*.mdb)';
- my $Desc = 'US T-Bond Quotes';
- my $Dir = 'i:\tmp\tpj';
- my $File = 'T-Bonds.mdb';
- my $Fullname = "$Dir\\$File";
-
- # Remove old database and dataset name
- unlink $Fullname if -f $Fullname;
- Win32::ODBC::ConfigDSN(ODBC_REMOVE_DSN, $Driver, "DSN=$DSN")
- if Win32::ODBC::DataSources($DSN);
-
- # Create new database
- my $Access = Win32::OLE->new('Access.Application', 'Quit');
- my $Workspace = $Access->DBEngine->CreateWorkspace('', 'Admin', '');
- my $Database = $Workspace->CreateDatabase($Fullname, dbLangGeneral);
-
- # Add new database name
- Win32::ODBC::ConfigDSN(ODBC_ADD_DSN, $Driver,
- "DSN=$DSN", "Description=$Desc", "DBQ=$Fullname",
- "DEFAULTDIR=$Dir", "UID=", "PWD=");
-
-This uses Win32::ODBC (described in TPJ #9) to remove and create
-F<T-Bonds.mdb>. This lets Mary use the same script on her workstation
-and on her laptop even when the database is stored in different
-locations on each. The program also uses Win32::OLE to make Microsoft
-Access create an empty database.
-
-Every OLE server has some constants that your Perl program will need
-to use, made accessible by the Win32::OLE::Const module. For instance,
-to grab the Excel constants, say C<use Win32::OLE::Const 'Microsoft
-Excel'>.
-
-In the above example, we imported the Data Access Object con-stants
-just so we could use C<dbLangGeneral>.
-
-=head2 MICROSOFT EXCEL
-
-Now Mary uses Win32::OLE a second time, to have Microsoft Excel create
-the chart shown below.
-
- Figure 1: T-Bond data generated by MicroSoft Excel via Win32::OLE
-
- # Start Excel and create new workbook with a single sheet
- use Win32::OLE qw(in valof with);
- use Win32::OLE::Const 'Microsoft Excel';
- use Win32::OLE::NLS qw(:DEFAULT :LANG :SUBLANG);
-
- my $lgid = MAKELANGID(LANG_ENGLISH, SUBLANG_DEFAULT);
- $Win32::OLE::LCID = MAKELCID($lgid);
-
- $Win32::OLE::Warn = 3;
-
-Here, Mary sets the locale to American English, which lets her do
-things like use American date formats (e.g. C<"12-30-98"> rather than
-C<"30-12-98">) in her program. It will continue to work even when she's
-visiting one of her international customers and has to run this
-program on their computers.
-
-The value of C<$Win32::OLE::Warn> determines what happens when an OLE
-error occurs. If it's 0, the error is ignored. If it's 2, or if it's 1
-and the script is running under C<-w>, the Win32::OLE module invokes
-C<Carp::carp()>. If C<$Win32::OLE::Warn> is set to 3, C<Carp::croak()>
-is invoked and the program dies immediately.
-
-Now the data can be put into an Excel spreadsheet to produce the
-chart. The following section of the program launches Excel and creates
-a new workbook with a single worksheet. It puts the column titles
-('Time', 'Open', 'High', 'Low', and 'Close') in a bold font on the
-first row of the sheet. The first column displays the timestamp in
-I<hh:mm> format; the next four display prices.
-
- my $Excel = Win32::OLE->new('Excel.Application', 'Quit');
- $Excel->{SheetsInNewWorkbook} = 1;
- my $Book = $Excel->Workbooks->Add;
- my $Sheet = $Book->Worksheets(1);
- $Sheet->{Name} = 'Candle';
-
- # Insert column titles
- my $Range = $Sheet->Range("A1:E1");
- $Range->{Value} = [qw(Time Open High Low Close)];
- $Range->Font->{Bold} = 1;
-
- $Sheet->Columns("A:A")->{NumberFormat} = "h:mm";
- # Open/High/Low/Close to be displayed in 32nds
- $Sheet->Columns("B:E")->{NumberFormat} = "# ?/32";
-
- # Add 15 minute data to spreadsheet
- print "Add data\n";
- $Range = $Sheet->Range(sprintf "A2:E%d", 2+$#Bars);
- $Range->{Value} = \@Bars;
-
-The last statement shows how to pass arrays to OLE objects. The
-Win32::OLE module automatically translates each array reference to a
-C<SAFEARRAY>, the internal OLE array data type. This translation first
-determines the maximum nesting level used by the Perl array, and then
-creates a C<SAFEARRAY> of the same dimension. The C<@Bars> array
-already contains the data in the correct form for the spreadsheet:
-
- ([Time1, Open1, High1, Low1, Close1],
- ...
- [TimeN, OpenN, HighN, LowN, CloseN])
-
-Now the table in the spreadsheet can be used to create a candle stick
-chart from our bars. Excel automatically chooses the time axis labels
-if they are selected before the chart is created:
-
- # Create candle stick chart as new object on worksheet
- $Sheet->Range("A:E")->Select;
-
- my $Chart = $Book->Charts->Add;
- $Chart->{ChartType} = xlStockOHLC;
- $Chart->Location(xlLocationAsObject, $Sheet->{Name});
- # Excel bug: the old $Chart is now invalid!
- $Chart = $Excel->ActiveChart;
-
-We can change the type of the chart from a separate sheet to a chart
-object on the spreadsheet page with the C<< $Chart->Location >>
-method. (This invalidates the chart object handle, which might be
-considered a bug in Excel.) Fortunately, this new chart is still the
-'active' chart, so an object handle to it can be reclaimed simply by
-asking Excel.
-
-At this point, our chart still needs a title, the legend is
-meaningless, and the axis has decimals instead of fractions. We can
-fix those with the following code:
-
- # Add title, remove legend
- with($Chart, HasLegend => 0, HasTitle => 1);
- $Chart->ChartTitle->Characters->{Text} = "US T-Bond";
-
- # Set up daily statistics
- $Open = $Bars[0][1];
- $High = $Sheet->Evaluate("MAX(C:C)");
- $Low = $Sheet->Evaluate("MIN(D:D)");
- $Close = $Bars[$#Bars][4];
-
-The with() function partially mimics the Visual Basic With statement,
-but allows only property assignments. It's a convenient shortcut for
-this:
-
- { # open new scope
- my $Axis = $Chart->Axes(xlValue);
- $Axis->{HasMajorGridlines} = 1;
- $Axis->{HasMinorGridlines} = 1;
- # etc ...
- }
-
-The C<$High> and C<$Low> for the day are needed to determine the
-minimum and maximum scaling levels. MIN and MAX are spreadsheet
-functions, and aren't automatically available as methods. However,
-Excel provides an Evaluate() method to calculate arbitrary spreadsheet
-functions, so we can use that.
-
-We want the chart to show major gridlines at every fourth tick and
-minor gridlines at every second tick. The minimum and maximum are
-chosen to be whatever multiples of 1/16 we need to do that.
-
- # Change tickmark spacing from decimal to fractional
- with($Chart->Axes(xlValue),
- HasMajorGridlines => 1,
- HasMinorGridlines => 1,
- MajorUnit => 1/8,
- MinorUnit => 1/16,
- MinimumScale => int($Low*16)/16,
- MaximumScale => int($High*16+1)/16
- );
-
- # Fat candles with only 5% gaps
- $Chart->ChartGroups(1)->{GapWidth} = 5;
-
- sub RGB { $_[0] | ($_[1] >> 8) | ($_[2] >> 16) }
-
- # White background with a solid border
-
- $Chart->PlotArea->Border->{LineStyle} = xlContinuous;
- $Chart->PlotArea->Border->{Color} = RGB(0,0,0);
- $Chart->PlotArea->Interior->{Color} = RGB(255,255,255);
-
- # Add 1 hour moving average of the Close series
- my $MovAvg = $Chart->SeriesCollection(4)->Trendlines
- ->Add({Type => xlMovingAvg, Period => 4});
- $MovAvg->Border->{Color} = RGB(255,0,0);
-
-Now the finished workbook can be saved to disk as
-F<i:\tmp\tpj\data.xls>. That file most likely still exists from when the
-program ran yesterday, so we'll remove it. (Otherwise, Excel would pop
-up a dialog with a warning, because the SaveAs() method doesn't like
-to overwrite files.)
-
-
- # Save workbook to file my $Filename = 'i:\tmp\tpj\data.xls';
- unlink $Filename if -f $Filename;
- $Book->SaveAs($Filename);
- $Book->Close;
-
-=head2 ACTIVEX DATA OBJECTS
-
-Mary stores the daily prices in her T-bonds database, keeping the data
-for the different contracts in separate tables. After creating an ADO
-(ActiveX Data Object) connection to the database, she tries to connect
-a record set to the table for the current contract. If this fails, she
-assumes that the table doesn't exists yet and tries to create it:
-
- use Win32::OLE::Const 'Microsoft ActiveX Data Objects';
-
- my $Connection = Win32::OLE->new('ADODB.Connection');
- my $Recordset = Win32::OLE->new('ADODB.Recordset');
- $Connection->Open('T-Bonds');
-
- # Open a record set for the table of this contract
- {
- local $Win32::OLE::Warn = 0;
- $Recordset->Open($Contract, $Connection, adOpenKeyset,
- adLockOptimistic, adCmdTable);
- }
-
- # Create table and index if it doesn't exist yet
- if (Win32::OLE->LastError) {
- $Connection->Execute(<<"SQL");
- CREATE TABLE $Contract
- (
- Day DATETIME,
- Open DOUBLE, High DOUBLE, Low DOUBLE, Close DOUBLE
- )
- SQL
- $Connection->Execute(<<"SQL");
- CREATE INDEX $Contract
- ON $Contract (Day) WITH PRIMARY
- SQL
- $Recordset->Open($Contract, $Connection, adOpenKeyset,
- adLockOptimistic, adCmdTable);
- }
-
-C<$Win32::OLE::Warn> is temporarily set to zero, so that if
-C<$Recordset->Open> fails, the failure will be recorded silently without
-terminating the program. C<Win32::OLE->LastError> shows whether the Open
-failed or not. C<LastError> returns the OLE error code in a numeric
-context and the OLE error message in a string context, just like
-Perl's C<$!> variable.
-
-Now Mary can add today's data:
-
- # Add new record to table
- use Win32::OLE::Variant;
- $Win32::OLE::Variant::LCID = $Win32::OLE::LCID;
-
- my $Fields = [qw(Day Open High Low Close)];
- my $Values = [Variant(VT_DATE, $Day),
- $Open, $High, $Low, $Close];
-
-Mary uses the Win32::OLE::Variant module to store C<$Day> as a date
-instead of a mere string. She wants to make sure that it's stored as
-an American-style date, so in the third line shown here she sets the
-locale ID of the Win32::OLE::Variant module to match the Win32::OLE
-module. (C<$Win32::OLE::LCID> had been set earlier to English, since
-that's what the Chicago Board of Trade uses.)
-
- {
- local $Win32::OLE::Warn = 0;
- $Recordset->AddNew($Fields, $Values);
- }
-
- # Replace existing record
- if (Win32::OLE->LastError) {
- $Recordset->CancelUpdate;
- $Recordset->Close;
- $Recordset->Open(<<"SQL", $Connection, adOpenDynamic);
- SELECT * FROM $Contract
- WHERE Day = #$Day#
- SQL
- $Recordset->Update($Fields, $Values);
- }
-
- $Recordset->Close;
- $Connection->Close;
-
-The program expects to be able to add a new record to the table. It
-fails if a record for this date already exists, because the Day field
-is the primary index and therefore must be unique. If an error occurs,
-the update operation started by AddNew() must first be cancelled with
-C<< $Recordset->CancelUpdate >>; otherwise the record set won't close.
-
-=head2 LOTUS NOTES
-
-Now Mary can use Lotus Notes to mail updates to all her customers
-interested in the T-bond data. (Lotus Notes doesn't provide its
-constants in the OLE type library, so Mary had to determine them by
-playing around with LotusScript.) The actual task is quite simple: A
-Notes session must be started, the mail database must be opened and
-the mail message must be created. The body of the message is created
-as a rich text field, which lets her mix formatted text with object
-attachments.
-
-In her program, Mary extracts the email addresses from her customer
-database and sends separate message to each. Here, we've simplified it
-somewhat.
-
- sub EMBED_ATTACHMENT {1454;} # from LotusScript
-
- my $Notes = Win32::OLE->new('Notes.NotesSession');
- my $Database = $Notes->GetDatabase('', '');
- $Database->OpenMail;
- my $Document = $Database->CreateDocument;
-
- $Document->{Form} = 'Memo';
- $Document->{SendTo} = ['Jon Orwant >orwant@tpj.com>',
- 'Jan Dubois >jan.dubois@ibm.net>'];
- $Document->{Subject} = "US T-Bonds Chart for $Day";
-
- my $Body = $Document->CreateRichtextItem('Body');
- $Body->AppendText(<<"EOT");
- I\'ve attached the latest US T-Bond data and chart for $Day.
- The daily statistics were:
-
- \tOpen\t$Open
- \tHigh\t$High
- \tLow\t$Low
- \tClose\t$Close
-
- Kind regards,
-
- Mary
- EOT
-
- $Body->EmbedObject(EMBED_ATTACHMENT, '', $Filename);
-
- $Document->Send(0);
-
-=head1 VARIANTS
-
-In this final section, I'll talk about Variants, which are the data
-types that you use to talk to OLE objects. We talked about this line
-earlier:
-
- my $Values = [Variant(VT_DATE, $Day),
- $Open, $High, $Low, $Close];
-
-Here, the Variant() function creates a Variant object, of type C<VT_DATE>
-and with the value C<$Day>. Variants are similar in many ways to Perl
-scalars. Arguments to OLE methods are transparently converted from
-their internal Perl representation to Variants and back again by the
-Win32::OLE module.
-
-OLE automation uses a generic C<VARIANT> data type to pass
-parameters. This data type contains type information in addition to
-the actual data value. Only the following data types are valid for OLE
-automation:
-
- B<Data Type Meaning>
- VT_EMPTY Not specified
- VT_NULL Null
- VT_I2 2 byte signed integer
- VT_I4 4 byte signed integer
- VT_R4 4 byte real
- VT_R8 8 byte real
- VT_CY Currency
- VT_DATE Date
- VT_BSTR Unicode string
- VT_DISPATCH OLE automation interface
- VT_ERROR Error
- VT_BOOL Boolean
- VT_VARIANT (only valid with VT_BYREF)
- VT_UNKNOWN Generic COM interface
- VT_UI1 Unsigned character
-
-The following two flags can also be used:
-
- VT_ARRAY Array of values
- VT_BYREF Pass by reference (instead of by value)
-
-B<The Perl to Variant transformation.> The following conversions are
-performed automatically whenever a Perl value must be translated into
-a Variant:
-
- Perl value Variant
- Integer values VT_I4
- Real values VT_R8
- Strings VT_BSTR
- undef VT_ERROR (DISP_E_PARAMNOTFOUND)
- Array reference VT_VARIANT | VT_ARRAY
- Win32::OLE object VT_DISPATCH
- Win32::OLE::Variant object Type of the Variant object
-
-What if your Perl value is a list of lists? Those can be irregularly
-shaped in Perl; that is, the subsidiary lists needn't have the same
-number of elements. In this case, the structure will be converted to a
-"rectangular" C<SAFEARRAY> of Variants, with unused slots set to
-C<VT_EMPTY>. Consider this Perl 2-D array:
-
- [ ["Perl" ], # one element
- [1, 3.1215, undef] # three elements
- ]
-
-This will be translated to a 2 by 3 C<SAFEARRAY> that looks like this:
-
- VT_BSTR("Perl") VT_EMPTY VT_EMPTY
- VT_I4(1) VT_R8(3.1415) VT_ERROR(DISP_E_PARAMNOTFOUND)
-
-B<The Variant To Perl Transformation.> Automatic conversion from Variants
-to Perl values happens as follows:
-
- Variant Perl value
- VT_BOOL, VT_ERROR Integer
- VT_UI1, VT_I2, VT_I4 Integer
- VT_R4, VT_R8 Float value
- VT_BSTR String
- VT_DISPATCH Win32::OLE object
-
-B<The Win32::OLE::Variant module.> This module provides access to the
-Variant data type, which gives you more control over how these
-arguments to OLE methods are encoded. (This is rarely necessary if you
-have a good grasp of the default conversion rules.) A Variant object
-can be created with the C<< Win32::OLE::Variant->new >> method or the
-equivalent Variant() function:
-
- use Win32::OLE::Variant;
- my $var1 = Win32::OLE::Variant->new(VT_DATE, 'Jan 1,1970');
- my $var2 = Variant(VT_BSTR, 'This is an Unicode string');
-
-Several methods let you inspect and manipulate Variant objects: The
-Type() and Value() methods return the variant type and value; the As()
-method returns the value after converting it to a different variant
-type; ChangeType() coerces the Variant into a different type; and
-Unicode() returns the value of a Variant object as an object of the
-Unicode::String class.
-
-These conversions are more interesting if they can be applied directly
-to the return value of an OLE method call without first mutilating the
-value with default conversions. This is possible with the following
-trick:
-
- my $RetVal = Variant(VT_EMPTY, undef);
- $Object->Dispatch($Method, $RetVal, @Arguments);
-
-Normally, you wouldn't call Dispatch() directly; it's executed
-implicitly by either AUTOLOAD() or Invoke(). If Dispatch() realizes
-that the return value is already a Win32::OLE::Variant object, the
-return value is not translated into a Perl representation but rather
-copied verbatim into the Variant object.
-
-Whenever a Win32::OLE::Variant object is used in a numeric or string
-context it is automatically converted into the corresponding format.
-
- printf "Number: %f and String: %s\n",
- $Var, $Var;
-
-This is equivalent to:
-
- printf "Number: %f and String: %s\n",
- $Var->As(VT_R8), $Var->As(VT_BSTR);
-
-For methods that modify their arguments, you need to use the C<VT_BYREF>
-flag. This lets you create number and string Variants that can be
-modified by OLE methods. Here, Corel's GetSize() method takes two
-integers and stores the C<x> and C<y> dimensions in them:
-
- my $x = Variant( VT_I4 | VT_BYREF, 0);
- my $y = Variant( VT_I4 | VT_BYREF, 0);
- $Corel->GetSize($x, $y);
-
-C<VT_BYREF> support for other Variant types might appear in future
-releases of Win32::OLE.
-
-=head1 FURTHER INFORMATION
-
-=head2 DOCUMENTATION AND EXAMPLE CODE
-
-More information about the OLE modules can be found in the
-documentation bundled with Win32::OLE. The distribution also contains
-other code samples.
-
-The object model for Microsoft Office applications can be found in the
-Visual Basic Reference for Microsoft Access, Excel, Word, or
-PowerPoint. These help files are not installed by default, but they
-can be added later by rerunning F<setup.exe> and choosing I<custom
-setup>. The object model for Microsoft Outlook can be found on the
-Microsoft Office Developer Forum at:
-http://www.microsoft.com/OutlookDev/.
-
-Information about the LotusScript object model can be found at:
-http://www.lotus.com/products/lotusscript.nsf.
-
-=head2 OLE AUTOMATION ON OTHER PLATFORMS
-
-Microsoft also makes OLE technology available for the Mac. DCOM is
-already included in Windows NT 4.0 and can be downloaded for Windows
-95. MVS and some Unix systems can use EntireX to get OLE
-functionality; see
-http://www.softwareag.com/corporat/solutions/entirex/entirex.htm.
-
-=head1 COPYRIGHT
-
-Copyright 1998 I<The Perl Journal>. http://www.tpj.com
-
-This article originally appeared in I<The Perl Journal> #10. It
-appears courtesy of Jon Orwant and I<The Perl Journal>. This document
-may be distributed under the same terms as Perl itself.