Beefy Boxes and Bandwidth Generously Provided by pair Networks
Clear questions and runnable code
get the best and fastest answer
 
PerlMonks  

Re: 'our' scoping

by eclark (Scribe)
on Jun 01, 2004 at 23:27 UTC ( #358801=note: print w/replies, xml ) Need Help??


in reply to 'our' scoping

This is my understanding of our.

use strict; package foo; our $bar = 1;

Is the same as...

use strict; package foo; use vars qw/$bar/; $bar = 1;

And the same as...

use strict; $foo::bar = 1;

And the same as...

package foo; $bar = 1;

Sorry for all the strict, but I wanted to show which ones work without a problem in strict. Please correct me if I'm wrong.

Replies are listed 'Best First'.
Re: Re: 'our' scoping
by thospel (Hermit) on Jun 02, 2004 at 03:08 UTC
    You're wrong :-)

    our makes a lexically scoped alias for a global. That means it remains in scope even if you change the package. Compare:

    use strict; package foo; our $bar = 1; # at this point, using $bar could mean TWO things: # 1) try to access the global $foo::bar # 2) try to access the alias named $bar for $foo::bar # The lexical (second) one wins in perl, so you don't # get a use strict error print $bar; package baz; # Now $bar could mean: # 1) try to access the global $baz::bar # 2) try to access the alias named $bar for $foo::bar # The lexical (second) one still wins. print $bar; # works, prints $foo::bar even though we are in baz
    with:
    use strict; package foo; use vars qw/$bar/; $bar = 1; # $bar has only one meaning, access $foo::bar print $bar; package baz; # $bar has only one meaning, access $baz::bar print $bar; #error

    To answer the original question, the documentation is right, the our (as used in the first code fragment) has no effect outside the file. But... you can still access the global $foo::bar from another file. But this is NOT using the "our" alias as you can for example see by trying to do in that other file:

    package foo; print $bar; # prints the global $foo::bar package baz; print $bar; # prints the global $baz::bar
    The lexical alias is gone, and $bar just accesses the global in the package that is in scope.
      Thankyou thankyou thankyou...

      You have fixed many confusions that I had. I thought that 'use vars' and 'our' were identical, and it did cause me some confusions because some of my code has a mixture of both (pre 5.6 and post 5.6).

      I went back and re-read the our documentation in the camel book and it is very precise, and now I understand (I think) what it is talking about.

      However, when I went back and re-read the use vars documentation in the camel book, I realize the source of my confusion...

      quote (my italics)

      use vars qw($frobbed @munge %seen);
      This pragma, once used to declare a global variable, is now somewhat deprecated in favor of the our modifier. The previous declaration is better accomplished using :
      our ($frobbed, @munge, %seen);
      ...

      No matter which of these you use, remember that they're talking about package globals, not file-scoped lexicals.

      This information had led me astray (it may be technically correct, but it confused me nonetheless).

      In closing, I would be really appreciative if you would turn your post into a mini-tutorial.

      Thanks,

      Sandy

Log In?
Username:
Password:

What's my password?
Create A New User
Domain Nodelet?
Node Status?
node history
Node Type: note [id://358801]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others pondering the Monastery: (4)
As of 2022-05-20 09:52 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?
    Do you prefer to work remotely?



    Results (73 votes). Check out past polls.

    Notices?