[Catalyst] MoreFewer

Vsevolod (Simon) Ilyushchenko simonf at cshl.edu
Mon Apr 24 14:09:23 CEST 2006


Here's version 0.01 of Catalyst::Plugin::MoreFewer.


Before I release it to CPAN, I would appreciate if more skilled people 
than I could look over the code and the example and tell me if either 
needs improvement.

This component helps your controller and forms deal with multiple rows 
of child fields (eg, a book can have many authors and many pages, and 
you might need to edit them all on one form). Specifically, it's very 
easy to have the buttons 'More' and 'Fewer' on the form to add or remove 
children without saving the data to the database.

The example is in t/lib/Recipe. It shows a list of dishes. You can run 
the test server using t/lib/scripts/recipe_server.pl. It will create a 
sqlite database in /tmp/recipe.db. The dish edit window has three kinds 
of children:

1. cooks - one-to-many table, children are deleted and recreated on 
every save,

2. food (=ingredients) - many-to-many table, children are deleted and 
recreated on every save, and

3. steps - one-to-many table that has to preserve child IDs, so they are 
NOT deleted on save.

The HTML template that uses More and Fewer buttons is 

Mst said on IRC that it would be good to split the component into the 
controller- and view- related parts, but I'm not quite sure how to do 
it. At least that remark prompted me to create a separate 
Catalyst::Model::ChildModel class (used internally) and simplify the API.

I'm also going to create Helpers that generate scaffolding code, but 
first I'd like to be sure I'm doing the right thing.

Some specific questions:

1. Are the names Catalyst::Plugin::MoreFewer and 
Catalyst::Model::ChildModel appropriate?

2. The sample application lives in t/lib as a separate Perl module 
distribution. It's a bit weird, but I see no other way, as it should not 
be a part of the main distribution.

3. Please criticize the approach I used in Recipe::Controller::Dish. The 
controller has to be able to return the current $c object and to tell 
MoreFewer if it's in data saving mode via the creating_data() and 
saving_data() methods. Hence, it has instance variables qw(c op class 
model), which are initialized in auto(). ('Class' and 'model' are there 
to make it look a little more generic.) In order to help auto() get the 
operation and class names from the URL, I have to use Regex actions 
instead of something simpler. I follow this approach in my other 
applications, and if there is a simpler way to achieve the same result, 
I sure would like to hear it.

4. Are there any other ways of dealing with children that I've missed?


Simon (Vsevolod ILyushchenko)   simonf at cshl.edu

"Think like a man of action, act like a man of thought."

                  Henri Bergson

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