Re^3: Subroutines with differing behaviour created from AUTOLOAD

This is a case when eval saves the day: (warning untested)

  die "No such method $AUTOLOAD. Barfing\n"
      unless exists $self->{$field};
  if ($self->{$field}{editable}) {
    *$AUTOLOAD = eval <<ENDSUB;
sub {
   my \$self = shift;
   \$self->{$field}{value} = shift if \@_;
   \$self->{$field}{value};
}
ENDSUB

  } else {
    *$AUTOLOAD = eval <<ENDSUB2;
sub {
    my \$self = shift;
    die "Can't modify readonly field '$field'" if \@_;
    \$self->{$field}{value};
}
ENDSUB2

  }
  goto &$AUTOLOAD;
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I'm Not Just Another Perl Hacker

Comment on Re^3: Subroutines with differing behaviour created from AUTOLOAD Download Code

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Re^4: Subroutines with differing behaviour created from AUTOLOAD by davis (Vicar) on Jun 08, 2004 at 15:13 UTC
That works (and is pretty damn cool, to boot), but doesn't it also negate the symbol table-insertion techniques? The `eval`'d code will have to be parsed anew each time the sub is called. davis It's not easy to juggle a pregnant wife and a troubled child, but somehow I managed to fit in eight hours of TV a day.	[reply]
Re^5: Subroutines with differing behaviour created from AUTOLOAD by rinceWind (Monsignor) on Jun 09, 2004 at 10:50 UTC
... but doesn't it also negate the symbol table-insertion techniques? The eval'd code will have to be parsed anew each time the sub is called. Not so. The evals return code references which are stuffed into the package symbol table to make accessor methods; a subsequent call to the same method will find it and not call AUTOLOAD. The purpose of the eval is to bind $field at the time AUTOLOAD happens. It does this as it is in the string passed to eval without an escape (all other variables are escaped). With the original, $field is not bound to a specific value, but forms a closure, and is bound to the calling pad (hence it will share values between instances). The eval solution gives you a fresh op tree each time AUTOLOAD is called. -- I'm Not Just Another Perl Hacker	[reply]