[Catalyst] Why is $c undefined?
Lukas Thiemeier
spamcatcher at thiemeier.net
Tue Oct 30 12:52:05 GMT 2012
Hi Craig,
You don't understand why "$c->model('Model1')" retrieves and data,
because it doesn't retrieve any data.
Database-code in the controller should be avoided, and instead be
implemented in the model.
My code just passes a reference to "Model2" to "Model1", so "Model1" can
access data from "Model2".
Within "Model1", you can use prepare, execute, fetch et cetera on
"Model1" and "Model2", to fetch the data for your calculations.
Nevertheless, i think that your idea to create a extra model, which has
access to both underlying databases, is a better choice.
Lukas
On 10/30/2012 01:16 PM, Craig Chant wrote:
> Thanks Lukas,
>
> Chained method calls is not my strong point in Perl, they seem easier to read in other languages with bracketed encapsulation and the dot notation.
>
> Your helper method is interesting, though I don't understand how $c->model("Model1"); retrieves any SQL data, like I said wrapping my head around this is a bit of an uphill struggle currently.
>
> Regards,
>
> Craig.
>
>
> -----Original Message-----
> From: Lukas Thiemeier [mailto:spamcatcher at thiemeier.net]
> Sent: 30 October 2012 11:28
> To: The elegant MVC web framework
> Subject: Re: [Catalyst] Why is $c undefined?
>
> Hi Craig,
>
> On 10/30/2012 12:09 PM, Craig Chant wrote:
>> Thanks Ian,
>>
>> The hierarchy is something that I am finding mind-blowing at the moment, "$self->jqgrid->render($self," , you are calling methods jqgrid->render on $self, passing in $self, I'm sure it makes sense to you :-)
>>
>
> No, he is calling "render" on whatever is returned by $self->jqgrid.
> Thats why $self has to be passed to "render". The code above is equivalent to:
>
> my $jqgrid = $self->jqgrid;
> $jqgrid->render($self, ...);
>
>
>> One thing I would like clarification with if possible.
>>
>> Where do I put code that requires the use of more than one model?
>>
>> Do I create a separate model that acts as an interface between the other models?
>
> Thats one possibility. Another possibility would be to create a helper method in Model1, which expects Model2 as a parameter.
>
> Model1.pm:
>
> sub calculate_sth_with_model2{
> my ($self, $model2) = @_;
> do_crazy_calculations();
> }
>
> And in your Controller:
>
> sub calculate :Local :Args(0) {
> my ($self, $c) = @_;
>
> my $m1 = $c->model("Model1");
> my $m2 = $c->model("Model2");
>
> $m1->calculate_sth_with_model2($m2);
>
> }
>
>>
>> You see I have two SQL servers in opposite ends of the country and so I have a model built on Model::DBI that can access one server and another Model that can access the other, but I have functionality that needs data from both , do some calculations and output accordingly.
>>
>> I assume this does not go in the controller, but I create an interface model with the required methods and functionality that the controller uses?
>>
>> Regards,
>>
>> Craig.
>>
>> -----Original Message-----
>> From: Ian Docherty [mailto:catalyst at iandocherty.com]
>> Sent: 30 October 2012 07:22
>> To: The elegant MVC web framework
>> Subject: Re: [Catalyst] Why is $c undefined?
>>
>> On 29 October 2012 21:01, Craig Chant <craig at homeloanpartnership.com> wrote:
>> ...
>>>
>>> I have read and seen frameworks such as Mojolicious encourage a shrinkage of the Model and move alot of functionality to the Controller, so there is a paradigm which seems to imply it is ok to do more stuff in the Controller, but I am leaning towards having the main code in the Model and then bolting it together via the Controller.
>>>
>> I can understand why you get this impression, I think a lot of people end up putting code in the Controller when they first start using MVC (I did so myself in the past).
>>
>> The Model should be external to your Catalyst app (or whatever framework you use) so that you can use it in things like cron jobs. It also makes testing easier if your Model is separate from your Catalyst app. Look at using something like Catalyst::Model::Adaptor as a thin shell to add your external Model into Catalyst.
>>
>> I am moving more and more into making my Controllers as thin as
>> possible. Logic that I might have previously put into the Controller,
>> I either put into the Model or I create helper functions. Here is an
>> example of a Controller (from Mojolicious as it happens but that is
>> not important)
>>
>> sub user_list {
>> my ($self) = @_;
>>
>> $self->jqgrid->render($self, {
>> rs => $self->schema->resultset('User')->search_rs,
>> filters => {},
>> rows => [qw(id name)],
>> });
>> }
>>
>> It's not important to know what is going on here, but this Controller gets a list of all users, formats the data for use in the jQuery jqGrid allows for sorting and filtering and outputs the data in JSON format. The point being, the controller code is kept simple and 'thin'
>> and yet it does a lot of work behind the scenes.
>>
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