http://qs321.pair.com?node_id=415798

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

If I am subclassing a module and I don't want some methods of the superclass to be accessible, how do I get rid of them? Can I delete them or should I just redefine them to call die? I don't have Damian's book handy...

Replies are listed 'Best First'.
Re: How to delete a method in a subclass?
by gaal (Parson) on Dec 17, 2004 at 22:47 UTC
    What do you want to happen if someone calls such a method?

    Anyway, yeah -- override the method in the subclass. Have it throw an exception, or do nothing. If you have lots of methods like that (then you should rethink your design, but) you can do something like 

    sub meth1 { obsoleted }
sub meth2 { obsoleted }
sub meth3 {}             # do nothing, quietly.
# [...]

sub obsoleted {
    require Carp;
    Carp::croak "obsoleted method called"; # exception, with stack tra
+ce

    # or, just complain but go on with the show.
    Carp::cluck "obsoleted method called";
}

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[d/l]

      I'm a fan of keeping the parenthesis for user-defined subroutines, and you give an example of why.

      Your methods will have the string "obsoleted" in them. With warnings enabled a warning will be issued. With strict enabled it'll be a fatal error.

      This is because when the methods are defined there is no &obsoleted subroutine and you don't indicate it's a subroutine in any way.

      Defining &obsoleted above the methods would solve this, but personally I'd just use parenthesis and not worry about where I define subroutines.

      ihb

      See perltoc if you don't know which perldoc to read!
      Read argumentation in its context!

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[d/l]
[select]
        Yes, that's a good point++.
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Re: How to delete a method in a subclass?
by kvale (Monsignor) on Dec 17, 2004 at 22:37 UTC
    Reaching into a superclass to mess with the symbol table is considered rude and is almost always bad programming practice. It is much preferable to override the method with your warning.

    -Mark

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Re: How to delete a method in a subclass?
by borisz (Canon) on Dec 17, 2004 at 22:38 UTC
    You can call die or whatever. But I guess subclass is not what you should do. You should create a new class and delegate the supported functions to a instance of your other class.
    Boris
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Re: How to delete a method in a subclass?
by Arunbear (Prior) on Dec 17, 2004 at 22:45 UTC
    You can't delete them because they don't exist in the package that defines your subclass.
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Re: How to delete a method in a subclass?
by Anonymous Monk on Dec 18, 2004 at 05:25 UTC
    I guess you just fire up the old text editor and delete the lines of code that define the methods.
[reply]
      Respectfully, I don't think that this is a very good idea.

      To be clear, if you delete the code in the base module, then when you or someone else goes to use that module in the future, it won't work.

      Far better to redefine the offending subs.

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