Re: Function reference undef when extract from hash?

[reneeb]

Do you use use strict and use warnings? Where do you call build_sth('set_to_flag')?

This works:

#!/usr/bin/perl

use strict;
use warnings;


build_sth( 'set_to_flag' );

sub write_flag{
    print "Success for flag.\n";
}

sub write_sets{print "Success for Set.\n"; }

sub do_nothing{print "Exit Here\n";}

sub build_sth{
    my ($op_code) = @_;
    
    my %Op = (
        set_to_flag => \&write_flag,
        set_tree => \&write_sets,
        default => \&do_nothing
    );
    
    my $op_exec = $Op{$op_code} ;
    if( defined $op_exec ){
        $op_exec->();
    }else{
        print "Oops\n";
    }

}

[Anonymous Monk]

I used strict and warning.

And the call of the build_sth('set_to_flag') in another function which is called in the main per script:

(continue with previous code)
sub somecall{
build_sth('set_to_flag')
}

somecall();

I have checked the previous version where I got trapped. I get the code fail when I move the hash outside of function:

my %Op = (
        set_to_flag => \&write_flag,
        set_tree => \&write_sets,
        default => \&do_nothing
    );
sub build_sth {
    my ($op_code) = @_;
    
    my $op_exec = $Op{$op_code} ;
    if( defined $op_exec ){
        $op_exec->();
    }else{
        print "Oops\n";
    }

}

why the code fail in this case?

[ikegami]

why the code fail in this case?

The only possibly reason is if build_sth('set_to_flag') is called before my %Op = ( ... ); is executed.

Otherwise, it doesn't fail.

sub write_flag { print "write_flag\n"; }
sub set_tree   { print "set_tree\n"; }
sub do_nothing { print "do_nothing\n"; }

... code you provided ...

build_sth('set_to_flag');  # Prints write_flag