http://qs321.pair.com?node_id=11135934


in reply to Not sure how to handle this scope

I wouldn't re-use the same variable name for a lexical that has already been defined. Also, don't put a postfix if on a my, as its behavior is undefined - see the note at the bottom of the section Statement Modifiers. Instead, you could do:

my $self = OO->new( $cat );
{
  my $inner_self = $ARGV[0] eq 'Fido' ? OO->new( $dog ) : $self;
  say $inner_self->species();
}

[download]

Note you shouldn't use Indirect Object Syntax either.

Update: Added some details to the above. Plus, why don't you just do this?

my $self = OO->new( $ARGV[0] eq 'Fido' ? $dog : $cat );

[download]

It's also a bit unusual to use $self as the variable name for a newly created object, since $self is usually used as the first argument to a method call, i.e. it's an existing object.

Replies are listed 'Best First'.
Re^2: Not sure how to handle this scope (updated)
by Anonymous Monk on Aug 18, 2021 at 18:13 UTC
    Strongly agree. "Re-using" a variable name, particularly one like $self, is a recipe for obtuse code that will be very difficult for your inevitable successor to understand and debug.
[reply]
      Thanks guys, I left out a lot of details- but the { } are actually a forked loop and the self that contains the mysql handle goes away for each fork. That's why I'm trying to do this- BUT I want to run sometimes forked , and sometimes not, and for the not case- I want to use the object from outside the loop.. I realize this if pretty fugly but there is a lot of motivation to do it.

      But aisde from all that the real question is why does self go undef, and not use the scope outside the braces?

[reply]

        Maybe give the inner variable a different name and assign it the value from the "main" handle in the non-fork case?

        my $main_dbh = DBI->connect(...);
while( 1 ) {
    my $dbh;
    if( $forked ) {
        $dbh = DBI->connect(...);
    } else {
        $dbh = $main_dbh;
    };
    $dbh->selectall_arrayref($sql);
}

        [download]
[reply]
[d/l]

In Section Seekers of Perl Wisdom