in reply to Re: Re: Re: Perl module symbol import versus direct invocation
in thread Perl module symbol import versus direct invocation

I agree it's very annoying that on the callee side, i.e. in the sub, it's virtually impossible to distinguish between being called as a function or as a method. Looks at the mess CGI.pm made of it — look into the subs "self_or_default" and "self_or_CGI".

A reason to have calls as class methods instead of as functions, is the simple fact that now, inheritance works. It doesn't when you call a sub as a function.

Two rather well known class methods are import, automatically invoked by use — and often inherited :-) from Exporter, and new, a name people often choose for a sub that serves to create a new instance of a class.

  • Comment on Re: Re: Re: Re: Perl module symbol import versus direct invocation

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Re^5: Perl module symbol import versus direct invocation
by adrianh (Chancellor) on Feb 26, 2003 at 14:00 UTC
    I agree it's very annoying that on the callee side, i.e. in the sub, it's virtually impossible to distinguish between being called as a function or as a method.
    {
    package Foo;
    use Devel::Caller qw(called_as_method);
    
    sub new { bless {}, shift }
    
    sub foo {
        my $arg = shift;
        if (called_as_method(0)) {
            ref($arg) ? "object method" : "class method";
        } else {
            "subroutine";
        }
    }
}

use Test::More tests => 3;

my $foo = Foo->new;
is( Foo->foo,       "class method" );
is( $foo->foo,      "object method" );
is( Foo::foo($foo), "subroutine" );

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    (although wanting to do this in real code is nearly always a sign that you need to rethink your design :-)

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