jeanluca has asked for the wisdom of the Perl Monks concerning the following question:

Dear Monks,

Here is an example of my module A.pm:
package A ;

sub new {
     my ($class, $type) = @_ ;
     "A:B$type"->new() ;
}

package A::B001 ;

sub new {
     ...
}

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This works great. But what if A::B001 does not exist ?
So my questions is how do I test this ?

Thanks a lot
Luca

Replies are listed 'Best First'.
Re: multiple package in one file
by friedo (Prior) on Mar 12, 2006 at 11:16 UTC
    You can see if a package exists by checking if its symbol table is defined. 

    package Foo;
$a = 1;
package main;
print "foo\n" if defined %Foo::;
print "bar\n" if defined %Bar::;

    [download]

    Note that the symbol table won't be defined until you put a symbol in it; a mere package declaration doesn't seem to do it.

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[d/l]
[select]
      So my problems is not solved then, because I need to check if the package exists before I use it ?
      Thnx
      Luca

      update: I see it, it works, but this doesn't seem to work:
      if ( defined %A::B$type ) {

}

      [download]
      Any suggestions ?
[reply]
[d/l]
        You'll need to use curlies to tell Perl that you want a variable as part of the package name.

        Try %{ 'A::B' . $type . '::' }

        Remember to include the extra '::' on the end.

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