Re^2: Moo error message not understood (BEGIN block missing)

[davies]

Thanks. Your advice works perfectly, but I'm still confused. I don't see how, if the "new" happens before "has", the text gets into the object as shown by Data::Dumper. Maybe I shouldn't be worrying, but I'm scared there's a trap lying in wait for me.

Regards,

John Davies

Update: Thanks again. I won't pretend to understand everything at first glance late on a Friday evening, but it's a relief to know that there is a sound explanation. I will work through it, but I won't guarantee how many attempts it will take to get it into my skull. I knew there were aspects of Perl I didn't have a clue about, and this is clearly one that I need to understand better.

[Anonymous Monk]

I'm still confused. I don't see how, if the "new" happens before "has", ..:)blah..

because line 7 (new) and line 10 (say) come before line 15 (has) and all three come after each use line

read use , require, do, eval, BEGIN, UNITCHECK, CHECK, INIT and END

Re: Non-traditional, Line by Line Compilation in Perl

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Maybe I shouldn't be worrying, but I'm scared there's a trap lying in wait for me.

:D  while( $fear ){ LEARN: { perldoc(); test(); }; $fear--; }

[Anonymous Monk]

the text gets into the object as shown by Data::Dumper.

Yes it does ... doesn't mean there is an accessor created (accessors are just "methods" aka "subroutines")

without has bar

use Data::Dump qw/ dd /;
dd( my $f = Foo->new(qw/ bar 1 /) );
$f->bar;
{package Foo; use Moo; }
__END__
bless({ bar => 1 }, "Foo")
Can't locate object method "bar" via package "Foo" at - line 3.

you can cheat and use $f->{bar} ... this is cheating / breaking encapsulation / peeking inside object / not using official api / so if sometime in the future you internally rename bar attribute to barps, anyone using ->{bar} would have to update program, anyone using the documented api ->bar wouldn't (because you'd update that too) ... yeah seems convoluted example but thats how they work :)

with has bar Without BEGIN block there is no bar accessor (accessor is subroutine ... all $obj->whatever is subroutines)

use Data::Dump qw/ dd /;
dd( my $f = Foo->new(qw/ bar 1 /) );
$f->bar;
{package Foo; use Moo; has( qw/ bar is rw / ); }
__END__
bless({ bar => 1 }, "Foo")
Can't locate object method "bar" via package "Foo" at - line 3.

with has bar and With BEGIN block no death :)

use Data::Dump qw/ dd /;
dd( my $f = Foo->new(qw/ bar 1 /) );
$f->bar;
BEGIN{package Foo; use Moo; has( qw/ bar is rw / ); }
__END__
bless({ bar => 1 }, "Foo")

with has bar and Without begin block no death (moved to line 1)

{package Foo; use Moo; has( qw/ bar is rw / ); }
use Data::Dump qw/ dd /;
dd( my $f = Foo->new(qw/ bar 1 /) );
$f->bar;
__END__
bless({ bar => 1 }, "Foo")

got that? See also perlobj, A Method is Simply a Subroutine, Attributes