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Re: GLOB reference problem

by ELISHEVA (Prior)
on Oct 05, 2009 at 08:47 UTC ( #799199=note: print w/replies, xml ) Need Help??


in reply to GLOB reference problem

The contents of %{...} are expected to be a reference and instead you have a glob.

Two changes I would make to the above code

  • Presumably FTP->new is returning an object reference, not a list, so my($this) should probably be simply my $this.
  • Assuming $this is an object reference and the object is implemented as a hash, %{*$this} should be simply %{$this} or even just %$this. See perlreftut for further information.

However, it is generally not good programming practice to break the opacity of an object reference. I would look more carefully at the docs for the FTP module and rewrite the code so that the hash assignment is unnecessary.

Best, beth

Replies are listed 'Best First'.
Re^2: GLOB reference problem
by jerryhone (Sexton) on Oct 05, 2009 at 10:26 UTC

    A bit more background...this code was originally written to utilise Net::FTP. However, I've needed to modify it as I need to run the code without actually FTPing anything outside the server, so I've created my own dummy FTP package. FTP->new (mine) is returning a HASH reference, but it looks like Net::FTP->new returns a GLOB reference.

    What construction's needed in my 'new' subroutine to return a GLOB reference. I have:-

    sub new { my ($pkg, $server, $user, $timeout, @args) = @_; my $self = { %fields }; my $ftp = bless $self, $pkg; $ftp->server($server); $ftp->user($user); $ftp->timeout($timeout); $ftp->initialize(); return $ftp; }

      When you want to extend an existing class, you have two options: inheritance and aggregation. If you go the inheritance route your new method would look something like this:

      use base qw(Net::FTP); #5.8 #or for 5.10 and up #use parent qw(Net::FTP); sub new { my ($pkg, $server, $user, $timeout, @args) = @_; # some special class specific stuff # ... is params for super class structure my $self = $pkg->SUPER::new(...); $self->server($server); $self->user($user); $self->timeout($timeout); $self->initialize(); # some special class specific stuff # if SUPER::new is well behaved, $self will be a member # of the $pkg class even though it was built by the # the super class. return $self; }

      If you go the aggregation route you might do something like this:

      sub new { my ($pkg, $server, $user, $timeout, @args) = @_; # some special class specific stuff # ... is params for super class structure my $ftp = Net::FTP->new(...); $ftp->server($server); $ftp->user($user); $ftp->timeout($timeout); $ftp->initialize(); my $self = { ftpHandle => $ftp }; return bless($self, $pkg); }

      If you want your own class to be implemented using a hash, you would go with the aggregation approach since Net::FTP doesn't return a hash. If you want to return the same kind of implementation as Net::FTP, then you would follow the inheritance pattern. You might find the sections on inheritance and aggregation in perltoot worth a read.

      Best, beth

        Thanks Beth.

        Unfortunately I need to completely avoid Net::Ftp. I don't want to extend that class - I need to create my own standalone class with the same interface.

        Jerry

Re^2: GLOB reference problem
by ikegami (Patriarch) on Oct 05, 2009 at 14:45 UTC

    The contents of %{...} are expected to be a reference and instead you have a glob.

    True, but that's not the cause of the error.

    The content of $this is expected to be a glob reference, but it's not.

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