Re: Arrow Operator and questions related to Path::Class

[kennethk]

in reply to Arrow Operator and questions related to Path::Class

Let's go line by through the code.

use Path::Class;

So, we'll use Path::Class. According to the linked docs, this use statement exports 2 functions: dir and file. So now we know anytime we see the function dir, we are invoking the one from Path::Class. From the docs:

dir

A synonym for Path::Class::Dir->new.

So the correct place to find docs on the object returned by dir is Path::Class::Dir. Let us continue:

# Iterate over the content of foo/bar
while (my $file = $dir->next) {

Now we've invoked the method next via an arrow dereference, so we check the appropriate package for the object for the method documentation. If you didn't realize it what package it was, you can use ref to tell you via the debug statement print ref $dir;.

$dir_or_file = $dir->next()

A convenient way to iterate through directory contents. The first time next() is called, it will open() the directory and read the first item from it, returning the result as a Path::Class::Dir or Path::Class::File object (depending, of course, on its actual type). Each subsequent call to next() will simply iterate over the directory's contents, until there are no more items in the directory, and then the undefined value is returned....

So now we have either a Path::Class::Dir or a Path::Class::File, depending on what the iterator hit. In both cases, methods by the name of stringify and is_dir are available and documented in the appropriate docs. When you get to the line

next if $file->is_dir();

we see next is not associated with a object dereference, so unless Path::Class exports something by that name, it will be a Perl CORE function. So, if we check the docs, either via the web at next or on the command line via perldoc -f next, we see it's a language keyword for flow control.

This is all recoverable if you follow the logical flow of the program.

[nemesdani]

Hey kennethk your wisdom spreads :)

http://stackoverflow.com/questions/12584342/perl-program-explained-line-by-line