Hi Rick, hope I got it right:
class AutomobileManufacturer < ActiveRecord::Base
has_many :automobiles
def favorite_automobiles
AutomobileCollection.from_association_collection automobiles
end
def all_automobiles
favorite_automobiles | remote_automobiles
end
def remote_automobiles
AutomobileCollection.from_webservice
end
end
class AutomobileCollection
def self.from_association_collection(collection)
collection = collection.map { |a| AutomobileItem.from_database a }
new collection
end
def self.from_webservice
# load collection... or take it as argument
collection = collection.map { |a| AutomobileItem.from_webservice
a }
new collection
end
# generate a hash to simplify intersect
def initialize(collection)
@collection_hash = collection.inject({}) { |hash, item|
hash.merge item.identifier => item
}
@collection = collection
end
# this could possibly be done with ruby stdlib 'Delegate'
def each(&block)
@collection.each(&block)
end
# intersect with another automobile collections
def |(other)
new_keys = other.automobiles_hash.keys - @collection_hash.keys
new_collection = @collection +
other.automobiles_hash.values_at(*new_keys)
self.class.new new_collection
end
class AutomobileItem
# two seperate methods because I think the interface for
# webservice automobile and database automobile wont match.
def self.from_webservice(automobile)
instance = new automobile.manufacturer # ...
instance
end
def self.from_database(automobile)
instance = new automobile.manufacturer # ...
def instance.favor
# nop ...
end
instance
end
def initialize(manufacturer, *further_attributes)
@attributes_hash = {
# ...
}
end
# generate an unique but compareable identifier
def identifier
"#{ manufacturer } ..."
end
# save the record, or maybe not when boxed automobile was loaded
from db...
def favor
Automobile.create @attributes_hash
# nop
def self.favor; end
end
end
end
To make a subclass of ActiveRecord::Base to something not subclassing
it requires some voodoo magic. If you really interested in this kind
of stuff you should gte yourself involved with the rubiunius project. ;)
Otherwise box them in something that would provide the same interface
for SOAPed objects as for ORMed objects.
This code is fully untested, but I hope you get the idea.
Regards
Florian
Am 02.01.2009 um 20:46 schrieb Rick:
>
> I understand I can just define a class without extending
> ActiveReord::Base, but what if I want to use the model object
> sometimes without having the data persist. For example...
>
> Let's say I have an "AutoManufacturer" object it might have
> name=Mercedes,etc. But AutoManufacturer could contain a collection of
> "Automobile" objects, (class=CLS, model="CLS350, numberOfDoors=4").
> Maybe your db isn't the one storing ALL the Automobile objects, you
> might only want to store 'favorite automobiles' but you still want to
> collect all the Automobile information (class, model, etc) when you
> record a favorite.
>
> So now what if I go to my DB and get my "AutoManufacturer" objects and
> for each AutoManufacturer I query some webservice to return a list of
> Automobiles and I want to then display on a page the AutoManufacturers
> and a collection of the Automobile objects I returned from my
> webservice call. If I have "Automobile" defined as an ActiveRecord
> type when I do something like....
>
> automobiles = getCarsFromWebservice()
> automobiles.each do |a|
> car = Automobile.new();
> car.class= a.class
> car.type= a.type
> autoManufacturer.autos << car
> end
>
> every new car created above and added to the autoManufacturer actually
> creates a new car in the db, In this case all I want is fully
> populated list of autos in each autoManufacturer object for use to
> display on the front end, but I don't really want the automobile added
> to the db at this time. (Maybe after they select some, I'll then query
> a webservice and populate a real Automobile that I do want to persist
> in my db.)
>
> Currently I'm having to do something really lame. I'm creating
> basically identical objects - one a model object and one a simple
> pojo. It doesn't seem very dry to do it this way though. What's a
> better approach?
>
> --
> Rick
>
> >
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