[Catalyst] How much chain?

[Ian Docherty]

Thomas Klausner wrote:
> ... do I need to hang myself?
>
> I'm (finally) playing around with chained, and like it very much.
> But now I have some sort of design question, on which I'd like to 
> collect some feedback:
>
> Say, you want to edit things. The general way of editing is the same for 
> most things, only the thingies you want to edit differ (i.e. their 
> fields).
>
> (slightly OT, but some background: We want to use HTML::FormFu 
> for actual form generation, but do not want to use the config-file 
> aproach, but something like a 'registry' where each field and it's 
> definition is stored (basically we have several different things using 
> similar fields...))
>
>
> What to you think is better:
> A) lots of chain
>
> package Thing:
> use base 'Generic';
> sub base : Chained('/') PathPart('thing') CaptureArgs(0) {}
> sub setup_fields : Chained('item') CaptureArgs(0) {
>     # define a list of fields and store them in stash
> }
>
> package Generic;
> sub item : Chained('base') PathPart('') CaptureArgs(1) {
>     # load thing and store in stash
> }
> sub show_form : Chained('setup_fields') Args(0) {
>     # take field list, make form, etc 
> }
>
> I'd end up with an URL like 
>   /thing/123/setup_fields/show_form
>   
I really don't think you should expose your implementation in your URI. 
For example if in the future you decide to re-write your system to not 
use FormFu and not have a setup_fields and a show_form method you have 
to change your interface. It is rather like the advantages you get by 
encapsulation in OO programming, you can change the internal 
implementation without worrying about the interface.
>
> B) Plain Old Methods
>
> package Thing:
> use base 'Generic';
> sub base : Chained('/') PathPart('thing') CaptureArgs(0) {}
> sub edit : Chained('item') Args(0) {
>     my ($self, $c) = @_;
>     $self->setup_fields($c, ... );
>     $self->make_form;
>     # 
> }
>
> package Generic;
> sub item : Chained('base') PathPart('') CaptureArgs(1) {
>     # load thing and store in stash
> }
> sub setup_fields {}
> sub make_form {}
> sub handle_form {}
>
> I'd end up with an URL like 
>   /thing/123/edit
> which IMO looks nicer.
>   
And IMO too. this is exactly how to use chaining. Don't hang yourself by 
trying to use chaining for everything.
>
> So, is A) just overdoing chained? B) looks ok, but is it using chained 
> to it's full potential?
>   
It is using chaining to it's full potential (given the simple example 
you gave) but in a more complex example, e.g.
/manufacturer/123/component/456/subcomponent/789/edit

it would be clearer that chaining is going to make something like this 
much easier by putting the manufacturer object on the stash, then the 
next chain puts the component object on, then the subcomponent, then it 
chains to the 'edit' controller.
> I'd really like to hear some of your thoughts...
>
>