On 04/21/2015 10:37 PM, mt1957 wrote:
L.s.
The following piece of code shows that one must be careful using my or
state variables in a class. They have the same behavior as an our
variable if I am right.
The difference is that 'our'-variables can be accessed from the outside
($A::p), 'my' and 'state'-varaibles can't.
The difference between 'my' and 'state' is that 'state' retains its
state (sic) between several executions of the block, but since a class
block is only executed once (while it's compiled), the distinction is
moot here.
Are they all kind of global to the class/object?
---
class A {
my $a;
has $.a;
our $p;
state $q;
method set ($b) {
$a = $b;
$!a = $b+10;
$p = $b+20;
$q = $b+30;
}
method get {
$!a //= 'undefined';
return "my=$a, has=$!a, our=$p, state=$q";
}
}
my $x = A.new;
$x.set(2); # Set variables in x object
say "X: ", $x.get;
my $y = A.new;
say "Y: ", $y.get; # Only attribute undefined
$y.set(4); # Set variables in y object
say "X: ", $x.get; # Modified in $x except for the attribute
---
The results are;
X: my=2, has=12, our=22, state=32
Y: my=2, has=undefined, our=22, state=32
X: my=4, has=12, our=24, state=34
Only the attribute is kept local to the object but all other variables
are shared between $x and $y.
Should one use only attributes in a class and use our variables to share
between objects?
If you want per-object local storage, use attributes, yes.
Cheers,
Moritz
