CODEWITHSUNDEEP
perl
fang yu
fang yu

Reputation: 481

What does the -> arrow do in Perl?

I keep seeing -> in code and I am not exactly sure what it means. For example:

@top_links = @{$m->links};

What does this line do? Also, where can I maybe read about it?

Upvotes: 46

Views: 83835

Answers (4)

flow2k
flow2k

Reputation: 4347

Perl arrow operator has one other use:

Class−>method invokes subroutine method in package Class

though it's completely different than your code sample. Only including it for completeness for the question in the title.

Upvotes: 7

Eugene Yarmash
Eugene Yarmash

Reputation: 149756

See The Arrow Operator in perlop:

"->" is an infix dereference operator, just as it is in C and C++. If the right side is either a [...], {...}, or a (...) subscript, then the left side must be either a hard or symbolic reference to an array, a hash, or a subroutine respectively. (Or technically speaking, a location capable of holding a hard reference, if it's an array or hash reference being used for assignment.) See perlreftut and perlref.

Otherwise, the right side is a method name or a simple scalar variable containing either the method name or a subroutine reference, and the left side must be either an object (a blessed reference) or a class name (that is, a package name). See perlobj.

Upvotes: 41

Paul Dixon
Paul Dixon

Reputation: 300825

The outer @{} part is a dereference - this implies $m->links is a reference to an array, so this operator deferences it to refer to the array directly, which is then copied to @top_links

Chapter 8 of the 'Camel Book' is a good place to learn about references, or the perlref section of the Perl documentation.

The -> arrow operator is an object dereference, in this case fetching the links member of the $m object. Similarly, later chapters of the Camel Book cover Perl's object oriented support in detail. See the perlobj section of the Perl documentation also.

Upvotes: 7

daxim
daxim

Reputation: 39158

In general, -> hints at dereference. This syntax comes from C.

In your example, it means method call: call method links from the object instance in $m. This is explained in the chapter Objects in Modern Perl. Pieces of perlsub, perlfaq7, perlobj, perltoot provide the details.

For references in general, search Stack Overflow; it is a recurring topic.

Upvotes: 15

Related Questions