[Phoenix-pm] wxPerl: Perl questions

[Michael Friedman]

Er, left off the list... Sorry.

______________________________________________________________________________
Mike Friedman | HighWire Press, Stanford Univ | friedman at highwire.stanford.edu

On Apr 13, 2011, at 12:12 PM, Michael Friedman wrote:

> Yep, that's exactly right. 
> 
> 'package' is file-scoped, until you hit another package statement or EOF, so it "contains" everything from there down. 
> 
> "package main;" is a special statement. Just like in C or Java (or probably other languages that I'm not as familiar with) the "main" package is the one that contains global definitions and handles command-line arguments and such. Effectively it's acting as an "end package" statement here, since Perl doesn't use braces around packages.
> 
> -- Mike F
> ______________________________________________________________________________
> Mike Friedman | HighWire Press, Stanford Univ | friedman at highwire.stanford.edu
> 
> On Apr 13, 2011, at 12:01 PM, leegold wrote:
> 
>> Hi,
>> 
>> So if "package" creates classes and thus namespaces then take the snip:
>> 
>> ...
>> package MyApp;
>> use base 'Wx::App';
>> sub OnInit {
>>   # parent window,  Window ID -1 means any,  # title,  # default
>>   position, # size
>>   my $frame = Wx::Frame->new(  undef,  -1, 'wxPerl rules', [-1, -1],
>>   [250, 150]);
>>   $frame->Show( 1 );
>> }
>> ...
>> 
>> Rewriting it a little. Could it be thought of like this ?:
>> 
>> package MyApp; # class MyApp
>> #{
>>   use base 'Wx::App';
>>   sub OnInit {
>>       # parent window,  Window ID -1 means any,  # title,  # default
>>       position, # size
>>       my $frame = Wx::Frame->new(  undef,  -1, 'wxPerl rules', [-1,
>>       -1], [250, 150]);
>>       $frame->Show( 1 );
>>   }
>> #} end class MyApp
>> 
>> Because that's what seems like is going on to me. And then further down
>> in the script the main namespace is re-established and a MyApp object is
>> instantiated...?
>> 
>> Thanks,
>> 
>> Lee G.
>> 
>> 
>> 
>> 
>> On Wed, 13 Apr 2011 10:50 -0700, "Michael Friedman"
>> <friedman at highwire.stanford.edu> wrote:
>>> leegold,
>>> 
>>> Newbie questions are our specialty!
>>> 
>>> First and foremost, a very good book that gives a good overview of what
>>> all this stuff means is _Modern Perl_, by chromatic. It's a free
>>> download, completely searchable, and easy to read, even for someone new
>>> to Perl.
>>> 	http://www.onyxneon.com/books/modern_perl/index.html
>>> 
>>>> 
>>>>> From a wxPerl program:
>>>> 
>>>> use Wx;
>>>> package MyApp;
>>>> use base 'Wx::App';
>>>> 
>>>> 
>>>> What is difference between a module and a package?
>>> 
>>> A module is a file on the filesystem containing Perl code. They usually
>>> end with .pm.
>>> 
>>> A package is the equivalent of a class in many other languages. You can
>>> have more than one package in a file, if you're being tricky. In general,
>>> there's one package per module and the module is named the same as the
>>> package. So "package MyApp;" is in the file "MyApp.pm". That way Perl can
>>> auto-locate the file containing the package when you use it from some
>>> other file. 
>>> 
>>> (A package isn't really a class -- it's just a way of segmenting code by
>>> giving it a namespace -- but modern perl uses packages in the same way
>>> other languages use classes, most of the time.)
>>> 
>>>> 
>>>> What exactly is MyApp? It's a package but I can't find any
>>>> documentation on it. There's no "MyApp" in my C:\Perl folder...
>>> 
>>> Your own modules go wherever you want them. So you don't find a MyApp.pm
>>> because you haven't saved this code in a file on your own computer yet.
>>> :-) 
>>> 
>>> Since the same syntax ('use <module>;') is used for loading both modules
>>> installed from CPAN and your own modules, it can sometimes be hard to
>>> tell which are which. I recommend naming your own modules with some
>>> top-level name that relates to the project/company/section/whatever so
>>> it's easier to tell the difference. I work for a company named
>>> "HighWire", so our custom modules are called like so:
>>> 
>>> 	package Highwire::Resource::Citation;
>>> 
>>> which is in a file in my home directory called
>>> ~/projects/Highwire/Resource/Citation.pm . That way it's easy to see
>>> which are modules I wrote and which are from CPAN.
>>> 
>>>> 
>>>> Tried to find info in "use base" keywords but no simple
>>>> explainations. What does "use base" do?
>>>> 
>>>> 
>>> 
>>> "use base" means that the named package is the parent of this package.
>>> When you're calling methods on an object, it'll search in the local
>>> package first and then start walking through everything in "use base". If
>>> you're using a version of perl > 5.10 (I think) you can also use "use
>>> parent" instead. 
>>> 
>>> http://perldoc.perl.org/base.html
>>> http://perldoc.perl.org/parent.html
>>> all the 'use' pragmas: http://perldoc.perl.org/index-pragmas.html
>>> 
>>> In this case, by having "use base Wx::App;", you're saying that "if you
>>> can't find a method in this file, go look in Wx::App, which probably has
>>> it." That's subclassing!
>>> 
>>> Good luck!
>>> -- Mike Friedman
>>> 
>>>> 
>>>> Here's the script:
>>>> 
>>>> # load wxPerl main module
>>>> use Wx;
>>>> # every application must create an application object
>>>> package MyApp;
>>>> use base 'Wx::App';
>>>> sub OnInit {
>>>> 
>>>>  # parent window,  Window ID -1 means any,  # title,  #
>>>> default position, # size
>>>>  my $frame = Wx::Frame->new(  undef,  -1, 'wxPerl rules', [-1,
>>>> -1], [250, 150]);
>>>> 
>>>>  $frame->Show( 1 );
>>>> }
>>>> package main;
>>>> # create the application object, this will call OnInit
>>>> my $app = MyApp->new;
>>>> # process GUI events from the application this function will not
>>>> # return until the last frame is closed
>>>> $app->MainLoop;
>>>> 
>>>> Thanks
>>>> _______________________________________________
>>>> Phoenix-pm mailing list
>>>> Phoenix-pm at pm.org
>>>> http://mail.pm.org/mailman/listinfo/phoenix-pm
>>> 
>