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23.5. Win32::OLE::Const
While browsing through the
documentation for an automation object, you may have come across
references to constant values. For example, if
you're trying to save an Excel workbook to a
different file format, you need to provide a file for- mat constant.
Since the server documentation typically provides symbolic con-
stants (e.g., xlExcel5 or
xlTemplate), we need a way to access those from
Perl. This is the purpose of Win32::OLE::Const, which imports the
constants from an automation object into your script.
You can either import the constants directly into your namespace as
subs that return the constant value, or you can have them returned as
a hash reference with the constant name as the key and its value as
the value. Here's an example of the former:
use Win32::OLE::Const ("Microsoft Excel");
print "xlExcel5 = ", xlExcel5, "\n";
This produces something like: xlExcel5 = 39
Here's an example
using the Load method to return a hash reference
populated with the constants and their values (this produces the same
output as the previ- ous example, of course):
use Win32::OLE::Const;
my $constants = Win32::OLE::Const->Load("Microsoft Excel");
print "xlExcel5 = $constants->{xlExcel5}\n";
Notice that, in both cases, we're supplying a
regular expression for the name of the type library from which we
want to import. Win32::OLE::Const searches the
registry for matching type libraries and loads the one with the
highest version number (you can override this by supplying the
version you want). You can also specify the language
you'd like. The parameters (for either
Load or Win32::OLE::Const) are
the typelib regular expression, the major version number, the minor
version number, and the locale (LCID).
You can also provide the Load method with an
automation object, which is then queried for its type library.
Interestingly, the documentation notes that this seems to be slower
than searching the Registry (though neither is really speedy with a
large automation server like Excel). Here's an
example of that:
use Win32::OLE;
use Win32::OLE::Const;
# Create an Excel application object
my $xl = Win32::OLE->new('Excel.Application', 'Quit') ||
die "Can't create Excel: ", Win32::OLE->LastError;
# Import the constants from it
my $constants = Win32::OLE::Const->Load($xl);
Using Load (to get a hash reference for the
constants) may be preferable to importing all of the constants into
your namespace. Some automation servers pro- vide a large number of
constants (the current version of Excel has some 900+), so importing
them into your namespace can clutter things considerably.
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| 23.4. Win32::OLE::Variant |  | 24. ODBC Extension for Win32 |
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