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

by davies (Vicar)
on Jan 17, 2014 at 19:35 UTC ( #1071010=note: print w/ replies, xml ) Need Help??


in reply to Re: Moo error message not understood (BEGIN block missing)
in thread Moo error message not understood

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.


Comment on Re^2: Moo error message not understood (BEGIN block missing)
Re^3: Moo error message not understood (begincheck.pl)
by Anonymous Monk on Jan 17, 2014 at 20:20 UTC
Re^3: Moo error message not understood (BEGIN block missing)
by Anonymous Monk on Jan 17, 2014 at 20:34 UTC

    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

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