Help passing reference to class subroutine in Perl - perl

Question

I am trying to pass a routine to another subroutine within a Perl module. But when I pass the sub reference the passed in ref no longer has the object data. Maybe its not possible to do it this way. The line I have a question about is the "unless" lines below:
sub get_flag_end {
my $self = shift;
return ( -e "$self->{file}" );
}
sub wait_for_end {
my $self = shift;
my $timeout = shift;
my $poll_interval = shift;
# Is it even possible to pass the oject subroutine and retain the objects data?
#unless ( $self->timeout( $timeout, $poll_interval, $self->get_flag_end ) ) { # does not work
unless ( $self->timeout( $timeout, $poll_interval, \&get_flag_end ) ) { # call happens but members are empty
die "!!!ERROR!!! Timed out while waiting for wait_for_end: timeout=$timeout, poll_interval=$poll_interval \n";
}
}
sub timeout {
my $self = shift;
my $timeout = shift;
my $poll_interval = shift;
my $test_condition = shift;
until ($test_condition->() || $timeout <= 0) {
$timeout -= $poll_interval;
sleep $poll_interval;
}
return $timeout > 0; # condition was met before timeout
}
I know that I could change the "get_flag_end" routine to take the value as an argument to the subroutine but what if there was a bunch of stuff done in "get_flag_end" and I needed more members from the object. I simplified the code a bit to make it a little easier to follow.

Answer 1

Just make a closure and pass that in:
sub wait_for_end {
my $self = shift;
my $timeout = shift;
my $poll_interval = shift;
my $callback = sub { $self->get_flag_end() };
unless ( $self->timeout( $timeout, $poll_interval, $callback ) ) {
die "!!!ERROR!!! Timed out while waiting for wait_for_end: timeout=$timeout, poll_interval=$poll_interval \n";
}
}
Update:
The other option is, since timeout is a method of the same class, pass in a method name.
sub wait_for_end {
my $self = shift;
my $timeout = shift;
my $poll_interval = shift;
my $callback = sub { $self->get_flag_end() };
unless ( $self->timeout( $timeout, $poll_interval, 'get_flag_end' ) ) {
die "!!!ERROR!!! Timed out while waiting for wait_for_end: timeout=$timeout, poll_interval=$poll_interval \n";
}
}
sub timeout {
my $self = shift;
my $timeout = shift;
my $poll_interval = shift;
my $method = shift;
# Do whatever
# Now call your method.
$self->$method();
}

Answer 2

In your $test_condition->() line, you are calling the subroutine but not passing it any arguments. Chances are what you meant was $test_condition->($self) or perhaps as $self->$test_condition
Here is a refactor of your code, correcting a few other issues:
sub get_flag_end {
my $self = shift;
return -e $self->{file}; # no need to quote the variable
}
sub wait_for_end {
my ($self, $timeout, $poll_interval) = #_; # unpack many args at once
unless ( $self->timeout( $timeout, $poll_interval, $self->can('get_flag_end') ) ) {
die "!!!ERROR!!! Timed out while waiting for wait_for_end: timeout=$timeout, poll_interval=$poll_interval \n";
}
}
sub timeout {
my ($self, $timeout, $poll_interval, $test_condition) = #_;
until ($self->$test_condition || $timeout <= 0) {
$timeout -= $poll_interval;
sleep $poll_interval;
}
return $timeout > 0; # condition was met before timeout
}
Depending on the rest of your implementation, creating a subroutine that knows its invocant might be better. You can do this in Perl with a closure:
unless ( $self->timeout( $timeout, $poll_interval, sub {$self->get_flag_end} )){
Here a new subroutine is created, which remembers the value of $self. You would call it without arguments $test_condition->()