Dynamic Package Name & Subroutine Call

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

Replies are listed 'Best First'.
Re: Dynamic Package Name & Subroutine Call by davido (Cardinal) on Dec 14, 2012 at 22:37 UTC
A package is just a namespace identified by a string. `package Test::One; sub hello{ my $var = shift; print "Hello: $var\n"; } 1; package Test::Two; sub hello{ my $var = shift; print "Hello: $var\n"; } 1; package main; use strict; use warnings; use Data::Dumper; my @pkgs = qw( One Two ); foreach my $pkg ( @pkgs ) { "Test::$pkg"->hello(); }` [download] This is one step toward full-fledged classes and objects, which may be a better solution in the longrun: perlobj. If you can't plan on passing the package name as the first parameter (which is what the `Class->method()` notation does), then you have to construct the fully qualified sub name, which means symbolic references and some ugly syntax: `foreach my $pkg ( @pkgs ) { no strict 'refs'; &{'Test::' . $pkg . '::hello'}($pkg); }` [download] Update: Good job on figuring out the symbolic ref syntax on your own. Looks like we both came up with the same. Dave	[reply] [d/l] [select]
Re^2: Dynamic Package Name & Subroutine Call by tobyink (Canon) on Dec 15, 2012 at 07:57 UTC
An alternative to `no strict 'refs'` would be: `foreach my $pkg ( @pkgs ) { my $hello = "Test::$pkg"->can('hello'); $hello->() if $hello; }` [download] ... because `can` returns a coderef. In the case of packages that have inheritance (`@ISA`) this will act slightly differently to `&{'Test::' . $pkg . '::hello'}()`. `perl -E'sub Monkey::do{say$_,for@_,do{($monkey=[caller(0)]->[3])=~s{::}{ }and$monkey}}"Monkey say"->Monkey::do'`	[reply] [d/l] [select]
Re^3: Dynamic Package Name & Subroutine Call by ikegami (Patriarch) on Dec 16, 2012 at 13:57 UTC
`can` should be used for methods and only for methods, so that should be `my $full_pkg = "Test::".$pkg; my $hello = $full_pkg->can('hello'); $full_pkg->$hello(...); # Or: $hello->($full_pkg, ...);` [download] which simplifies to: `my $full_pkg = "Test::".$pkg; $full_pkg->hello(...);` [download] You don't even need `can` if the method name is variable. `$full_pkg->$method_name(...);` [download]	[reply] [d/l] [select]
Re^4: Dynamic Package Name & Subroutine Call by Anonymous Monk on Dec 17, 2012 at 08:51 UTC
Re^5: Dynamic Package Name & Subroutine Call by ikegami (Patriarch) on Dec 17, 2012 at 13:06 UTC
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Re: Dynamic Package Name & Subroutine Call by awohld (Hermit) on Dec 14, 2012 at 22:32 UTC
By George, I think I just figured it out: CHANGE: `Test::$pkg::hello($pkg);` [download] TO: `{ no strict 'refs'; &{"Test::" . $pkg. "::hello"}($pkg); }` [download]	[reply] [d/l] [select]
Re^2: Dynamic Package Name & Subroutine Call by ikegami (Patriarch) on Dec 16, 2012 at 13:55 UTC
The following works with strict on: `(\&{"Test::${pkg}::hello"})->($pkg);` [download] The same, but more readable: `my $sub = \&{"Test::${pkg}::hello"}; $sub->($pkg);` [download] Then again, explicitly using `no strict 'refs';` might be better a good thing. That said, it looks like you have a method call (to which you're passing the wrong package name). If so, you should be using `("Test::".$pkg)->hello(...);` [download]	[reply] [d/l] [select]