poop question

leocharre has asked for the wisdom of the Perl Monks concerning the following question:

if i make a singleton object, and it returns a reference to a global variable within it- that can be changed without using the object's methods... is it defeating the whole purpose of using poop ?

i just started playing with poop. and it's kind of weird for me. grandfather sugested i use it in my quest of having global vars in a project- but i wanted to uhm.. not be too messy with the symbol tables, and i read that globals are bad juju.

i have this hash %FRIDGE and it has stuff in it, i want to put and take stuff out of it, and any module code that uses House/Kitchen/Fridge.pm to use the same fridge and see the same data that other code may have modified.

there are lots of ways code may want to take a banana out of the fridge, and i want to allow other people to easily implent ways of putting stuff in

Comment on poop question

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Re: poop question by friedo (Prior) on Feb 21, 2006 at 22:35 UTC
You can avoid the use of package globals in a singleton object by using a lexical. For instance: `package My::Singleton; my $DATA; sub get_data { my $class = shift; $class->_init unless defined $DATA; return bless $DATA, $class; } sub _init { $DATA = { foo => 42 }; }` [download] Because `$DATA` is a lexical ("my") variable, it's only accessable to the subroutines defined in its scope. (In this case, a file scope, but you could add a bare block to hide it from other parts of the same file if you really want to.) See also Class::Singleton.	[reply] [d/l] [select]

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Re: poop question
by friedo (Prior) on Feb 21, 2006 at 22:35 UTC

package My::Singleton;

my $DATA;

sub get_data { 
    my $class = shift;
    $class->_init unless defined $DATA;
    return bless $DATA, $class;
}

sub _init { 
    $DATA = { foo => 42 };
}
[download]

$DATA

Class::Singleton

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