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Re: Function reference undef when extract from hash?

by reneeb (Chaplain)
on Mar 03, 2008 at 11:09 UTC ( #671635=note: print w/replies, xml ) Need Help??

in reply to Function reference undef when extract from hash?

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"; } }

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Re^2: Function reference undef when extract from hash?
by Anonymous Monk on Mar 03, 2008 at 18:25 UTC

    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?

      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

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