Dan Muey wrote:
> Howdy list!
>
> Within a module function that can be exported I use a function, say
> header() from CGI.
> IN that module I have to have
> use CGI qw(header);
> OK super.
> What about if I have a function I export that uses a function from
> say, the DBI module, and the
> first argument sent to it is the Data Base Handle Variable like so:
>
> Script:
> use DBI;
> use MyFunkyModule qw(databasestuff);
> my $dbh DBI->connect.....
>
> print databasestuff($dbh,$query);
>
> MyFunkyModule.pm:
>
> sub databasestuff {
> my $dbh = shift;
> my $query = shift;
> return $dbh->do($query);
> }
> (I realize that in this case I might As well just do do() but it's
> just an example to illustrate the idea)
>
> Would I still have to have use DBI; in the package MyFunkyModule; in
> MyFunkyModule.pm?
No, not in the example you've shown.
>
> Basically I'd like to export functions that use uncommon modules.
> I'd like those functions to fail with an error if they don't have
> them installed or give they are given a bad object, IE like if $dbh
> was a simple string in my example above..
>
> I supposed I could do and eval on the module inside the function:
>
> sub databasestuff {
> eval { use DBI; };
You have to use "require" instead of "use" in a case like this, because
"use" is a compile-time thing.
> die "You need DBI installed to use this function $@" if($@);
> my $dbh = shift;
> my $query = shift;
> return $dbh->do($query);
> }
> (Yes I know DBI is a standard module, I'm just using it as an example
> since most people know how to use it)
>
> But if the just sending $dbh part of the object would work so I
> wouldn't have to use() it in MyFunkyModule.pm that'd be great.
If you want to know if $dbh is actually a database handle, you can use:
die "Not a DBI database handle" unless UNIVERSAL::isa($dbh, 'DBI::db');
You can also check to see if $dbh supports a "do" method before calling it:
die "Object doesn't have a 'do' method" unless UNIVERSAL::can($dbh,
'do');
This won't work if do is an autoloaded method (which it isn't in DBI). In
that case, wrapping the method call in eval() is the way to go.
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