new callbacks for CouchRest

[Matt Aimonetti]

As part of my couchrest refactoring required for assay-depot (client),
I implemented the new Rails3 callback systems in CR.

Here is an example of a CouchRest::ExtendedDocument class using
validation

class Card < CouchRest::ExtendedDocument
# Include the validation module to get access to the validation
methods
include CouchRest::Validation

# Set the default database to use
use_database TEST_SERVER.default_database

# Official Schema
property :first_name
property :last_name, :alias => :family_name
property :read_only_value, :read_only => true

timestamps!

# Validation
validates_present :first_name

end

Validation uses a before filter to validate your objects.

If you look at lib/more/extended_document.rb you will notice that we
have 2 callbacks defined by default:

define_callbacks :save
define_callbacks :destroy

You can use one of these callbacks easily as shown below:

save_callback :before, :log_stuff

Here is the implementation of #save in ExtendedDocument

# Trigger the callbacks (before, after, around)
# and save the document
def save(bulk = false)
caught = catch(:halt) do
_run_save_callbacks do
save_without_callbacks(bulk)
end
end
end

If you want to make a filter halt, just do: throw(:halt)

In the case of above save method, it makes sense to throw(:halt,
false) so if the a fails save will be false.

When you include CouchRest::Validation to a class, the following code
is evaluated:

if (method_defined?(:save) && method_defined?
(:_run_save_callbacks))
save_callback :before, :check_validations
end

def check_validations(context = :default)
throw(:halt, false) unless context.nil? || valid?(context)
end

You might wonder about the contexts, well... it's not fully
implemented, so let's talk about that later ;)


I know Chris wanted to get rid of the Extlib dependency so I'm glad to
say that we potentially don't need Extlib hooking system as we have a
better one available in CR :)

Before I forget, if you want to use the callback system on a non CR
class, just include CouchRest::Callbacks, 100% pain free :)

- Matt

http://github.com/mattetti/couchrest/commit/fec21c3ff326d94f884ef3ac18bbdbd875a56492

[Chris Anderson]

On Tue, Feb 3, 2009 at 6:20 PM, Matt Aimonetti <mattAi...@gmail.com> wrote:
>
> As part of my couchrest refactoring required for assay-depot (client),
> I implemented the new Rails3 callback systems in CR.
>

This looks really solid. With these callbacks, we can run lean without
extlib and still implement a lot of interesting stuff.

>
> You might wonder about the contexts, well... it's not fully
> implemented, so let's talk about that later ;)

Do tell. ;)

Chris

--
Chris Anderson
http://jchris.mfdz.com

[Matt Aimonetti]

As a teaser, think about the fact that your documents might look different based on the context, a personal card for instance will be different if it's a business card or if it's a card you give to your friends and family.

At a couch level, it doesn't matter, but at your app level when we get into the whole validation, STI business, it might be pretty helpful.

Anyways, that's not on the top of my TODO list yet, once I'm done with revisiting the casting process, I'll come back to that later on. (the implementation should be pretty trivial)

- Matt

[Chris Anderson]

On Tue, Feb 3, 2009 at 7:06 PM, Matt Aimonetti <mattai...@gmail.com> wrote:
> As a teaser, think about the fact that your documents might look different
> based on the context, a personal card for instance will be different if it's
> a business card or if it's a card you give to your friends and family.
>

So is it like, casting by ducktype? Sounds like fun.

I like to think of each key, as having the type, in my data mining
applications. So then different docs will have different composite
types, depending on the top level keys they utilize.

A doc might be a collection of application metadata, document data,
user data, and suchlike. Attaching methods to key names regardless of
class or type, might be flexible and useful.