[Catalyst] Global 'helper' methods

Lukas Thiemeier spamcatcher at thiemeier.net
Tue Oct 30 15:24:00 GMT 2012 

Hm... how to measure the overhead of a module?

There is a XS version of the module which is used if you have a C
compiler. I don't know the exact overhead, but I know that it is fast.

I have no experience with the pure perl version of that module.

If all you have to do with the dates is the simple string transformation
you are right. As I said before: I recommend to use DT if you are
working with dates a lot. Doing math on dates and times is annoying,
because of leap years, epochs, timezones and so on. If you need this:
Using DateTime is recommended. If not: Its not :)

If you are ONLY using pure perl modules:
You can include all required modules in your distribution. It should run
on any perl installation, even in a shared host environment.

App::FatPacker helps you doing this...

But this doesn't work as soon as you use XS modules.

On 10/30/2012 04:03 PM, Craig Chant wrote:
> Thanks Lukas,
> 
> I appreciate there is DateTime , though I have so much legacy code that uses my helper class re-writing everything will be a mammoth task.
> 
> I hand rolled a lot when I first started out with Perl, didn't know much about CPAN or PPM, and couldn't load any modules that weren't part of the core install on the original 'shared' hosting I was using.
> 
> Plus I always felt loading an entire module to re-arrange a tiny string seems a bit OTT?
> 
> Dunno, what's the overhead of DateTime?
> 
> Craig.
> 
> -----Original Message-----
> From: Lukas Thiemeier [mailto:spamcatcher at thiemeier.net]
> Sent: 30 October 2012 14:52
> To: catalyst at lists.scsys.co.uk
> Subject: Re: [Catalyst] Global 'helper' methods
> 
> You can also define your constants in "YourApp/Constants.pl", and "use"
> YourApp::Constants wherever you need them.
> 
> YourApp/Constants.pm:
>   use constant { FOO => 1 };
>   1;
> 
> Controller.pm:
> 
>   use YourApp::Constants;
> 
>   # and in some method
>   ...
>   my $global_foo = FOO;
> 
> There might be a better way, but this works...
> 
> For handling dates, I recommend "DateTime", available on cpan:
> 
> Another reason to use DBIC:
> DBIx::Class::Inflatecolumn::DateTime automatically transforms dates stored in a database into a DateTime object, which can be used like this:
> 
> my $uk_string = $datetime->dmy('/');
> my $us_string = $datetime->ymd('-');
> 
> But DateTime is not related to DBIC, DBIC just makes using it easy.
> 
> Use it if you have to work with dates a lot. It has lots of methods for outputting dates, times or both in different formats, and it allows datetime-math...
> 
> 
> On 10/30/2012 03:39 PM, Craig Chant wrote:
>> Well I opted for putting my globals (methods and constants) in
>> MyApp.pm
>>
>> It's working grand with $c->myMethod or $c->MY_CONSTANT
>>
>> I use to have them working as a bareword within my application , but $c->MY_CONSTANT is just as easy!
>>
>> Many thanks for all the input and help, it really is appreciated.
>>
>> -----Original Message-----
>> From: Lukas Thiemeier [mailto:spamcatcher at thiemeier.net]
>> Sent: 30 October 2012 13:56
>> To: catalyst at lists.scsys.co.uk
>> Subject: Re: [Catalyst] Global 'helper' methods
>>
>> Hi Craig,
>>
>> Writing helpers in your main App.pm and using roles is not either-or.
>>
>> Roles are one possibility to modify your classes in a reusable way.
>>
>> If your helpers are really global, which means that they are used by all, or almost all your controllers, I would put them into your main application class.
>>
>> If you have more than one application which make use of the same
>> helpers: Put them into a role:
>>
>> YourHelperRole.pm:
>>
>>   package YourHelperRole;
>>   use Moose::Role;
>>
>>   has "some_attribute" => ( ... ); # if you need attributes
>>
>>   sub helpermethod1{
>>         my ($self, $other, $args) = @_;
>>         do_something();
>>   }
>>
>>   sub helpermethod2{
>>         my ($self, $other, $args) = @_;
>>         do_something_different();
>>   }
>>
>>   no Moose::Role; # or use namespace::autoclean or MooseX::MarkAsMethod
>>   1;
>>
>> App.pm:
>>
>>   use Catalyst qw( ... );
>>   extends "Catalyst";
>>   with qw/YourHelperRole/;
>>
>>   ...
>>
>> In my opinion, extending your main App.pm with roles is only useful if you need the same helpers in different locations, too.
>> If you only need them for that single application,  avoid the overhead related to using roles.
>>
>> If you have helpers which are only needed by some controllers, create a role for your controllers. You can not only implement helpers in you roles, you can also create method-modifiers, which change the way your methods behave.
>>
>> Here is an example, which writes sth to the log, after the "delete"
>> method was called:
>>
>> YourLogRole.pm:
>>
>>   package YourLogRole;
>>
>>   use Moose::Role;
>>   requires qw/delete/; #die if the consuming class has no "delete"
>>
>>   after "delete" => sub{
>>         my ($self, $c) = @_;
>>         $c->log->debug("DELETE called");
>>   };
>>
>>   no Moose::Role;
>>   1;
>>
>> Controller1.pm: (has the helpers, but no logging)
>>
>>   package Controller1;
>>   use Moose;
>>   extends "Catalyst::Controller";
>>   with qw/
>>         YourHelperRole
>>   /;
>>
>>   sub someaction :Local {
>>         my ($self, $c) =@_;
>>         $self->helpermethod1();
>>   }
>>
>>   ...
>>
>> Controller2.pm: (has helpers AND logging)
>>
>>   package Controller2;
>>   use Moose;
>>   extends "Catalyst::Controller";
>>   with qw/
>>         YourLogRole
>>         YourHelperRole
>>   /;
>>
>>   sub delete :Local :Args(1) { ... }
>>
>> Controller3.pm (has logging, but no helpers)
>>
>>   package Controller3;
>>   use Moose;
>>   extends "Catalyst::Controller";
>>   with qw/
>>         YourLogRole
>>   /;
>>
>>   sub delete :Local :Args(1) { ... }
>>
>> Roles are very powerful tools. I use them a lot.
>> Read the Moose docs for more information.
>>
>> If you don't want to learn Moose, roles and so on now, just remember:
>>
>> 1. write sth in a role
>> 2. consume the role in a moose class, using "with"
>> 3. your roles methods and attributes will be available in the
>> consuming class
>>
>> Lukas
>>
>> On 10/30/2012 02:03 PM, Craig Chant wrote:
>>> Hi,
>>>
>>>
>>>
>>> Please could you advise the best way of having a global 'helper'
>>> class that has all commonly used methods in it accessible for any
>>> part of the catalyst app.
>>>
>>>
>>>
>>> I found this thread
>>> http://stackoverflow.com/questions/11941836/catalyst-global-subroutin
>>> e
>>> s
>>>
>>>
>>>
>>> With one indicating it's ok to put them in the main MyApp.pm and
>>> another saying to use Moose & Roles.
>>>
>>>
>>>
>>> What is considered the correct way and could you provide an example
>>> of how I create this helper class and bolt it to the Catalyst application.
>>>
>>>
>>>
>>> Many thanks,
>>>
>>>
>>>
>>> */Craig Chant/*
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