Sub on the fly?

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

Ye monks who doth perl encode!

Can I add functions to a package on the fly? For example, could something like this be made to work?

package blort;

sub add_method {
    my $name = shift;
    ## Do some Magic
}

...

use blort;

blort::add_method('foo');
blort::foo();
[download]

I want to know how things like Class::MethodMaker and similer things work. Class::MethodMaker creates the subs at compile time. Is it possible to add subs during run time?

Thanks!
-Pileofrogs

Update: You all rock!! ++ all round! Thanks!

Comment on Sub on the fly? Download Code

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Re: Sub on the fly? by liverpole (Monsignor) on Aug 16, 2006 at 23:07 UTC
Hi pileofrogs, There was this node, by flogic, on that very subject, written just recently. Have you had a chance to read it yet? s''(q.S:$/9=(T1';s;(..)(..);$..=substr+crypt($1,$2),2,3;eg;print$..$/	[reply]
Re: Sub on the fly? by chromatic (Archbishop) on Aug 16, 2006 at 23:08 UTC
Sure, see Sub::Installer.	[reply]
Re^2: Sub on the fly? by stvn (Monsignor) on Aug 17, 2006 at 11:52 UTC
Personally I prefer Sub::Install since it does not futz with UNIVERSAL to get the job done. -stvn	[reply]
Re: Sub on the fly? by ysth (Canon) on Aug 16, 2006 at 23:08 UTC
Yes, usually with something like `*foo = sub { ... };`	[reply] [d/l]
Re^2: Sub on the fly? by stvn (Monsignor) on Aug 17, 2006 at 12:14 UTC
However, that would only work if you were within the `blork` package, so if you wanted to install the method from `main::` then this `*blork::foo = sub { ... }` is more approriate. -stvn	[reply] [d/l] [select]
Re^3: Sub on the fly? by phaylon (Curate) on Aug 17, 2006 at 15:41 UTC
Well, assuming that most of these things will happen dynamically, I'll raise yours by `{ no strict 'refs'; { $class . '::' . $name } = sub { ... }; }` [download] scnr* Update: As you already did below. slaps-self Ordinary morality is for ordinary people. -- Aleister Crowley	[reply] [d/l]
Re: Sub on the fly? by stvn (Monsignor) on Aug 17, 2006 at 12:11 UTC
I want to know how things like Class::MethodMaker and similer things work. Class::MethodMaker creates the subs at compile time. Is it possible to add subs during run time? Yes, it is possible to do this at runtime. Basically you need to access the symbol table, which can be done like so (altering your code somewhat). `sub add_method { my $class = shift; my $name = shift; my $code = shift; no strict 'refs'; # because you should have strict on *{$class . '::' . $name} = $code; }` [download] Then you can do the following: `# you must call this as a method, and pass it a CODE ref blort->add_method('foo', sub { print 'bar' }); # now you can do this ... blort::foo();` [download] Of course there are a number CPAN modules you could use to do this; Sub::Install, Sub::Installer, Class::Accessor, etc. -stvn	[reply] [d/l] [select]
Re: Sub on the fly? by kwaping (Priest) on Aug 16, 2006 at 23:27 UTC
I admit I'm confused... How is what you want different than the functionality `AUTOLOAD` provides? --- It's all fine and dandy until someone has to look at the code.	[reply] [d/l]
Re^2: Sub on the fly? by stvn (Monsignor) on Aug 17, 2006 at 11:59 UTC
Well to start with, perl's method dispatch will first look for an inherited method, then go to AUTOLOAD, so if the OP wants to override a method locally they could not do this with AUTOLOAD. Also, using AUTOLOAD has a signifigant performance hit, which depending on the complexity of your AUTOLOAD function can easily be something like 4x slower. Not to mention the programmer complexity hit, even the simplest AUTOLOAD function is harder to understand and reason about then a set of simple methods. IMO, AUTOLOAD should be a last resort for when you really don't know the names of the methods to be called, and not a tool for reducing typing. -stvn	[reply]