Absolutely having class methods/data is ok.

This does not break encapsulation. You're simply calling the method on the class, instead of an instance (object) of the class.

This in fact is quite common. Imagine you have a class that counts its objects. The count variable would be a class var, and you could just write a class method that returns that value. Note here that when writing class methods, you have to realize that the first param will be the module name, not a blessed instance, so you won't have $self to operate on.

Class methods don't break encapsulation, and if you ever changed $count, you'd refactor the class method to return the right thing, instead of changing scripts that reference $Module::count directly.

Class methods also provide you the ability to do things with a module without having to instantiate a new object:

sub new {
    return bless {}, shift;
}
sub add {
    shift; # throw away object/class; not needed
    my ($x, $y) = @_;
    return $x + $y;
}

[download]

Now you can add() in either of these ways:

my $res = Module->add(1, 2);

# or

my $obj = Module->new;
my $res = $obj->add(1, 2);

# or even

my $mod = 'Module';

my $res = $mod->add(1, 2);

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I use the latter form of calling class methods in my unit tests, especially when creating numerous objects within the same test file:

my $mod = 'My::Long::Module::Name';

{ # test 1
    my $obj = $mod->new;
}
{ # test 2
    my $obj = $mod->new;
}

# etc

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In reply to Re^3: Passing the logger's object (updated) by stevieb
in thread Passing the logger's object by v_melnik

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