John Feminella <johnf@...> writes:
>
> Suppose that we have Radio Stations which play Songs by means of a License.
>
> =======
> class Song
> has_many :licenses
> has_many :radio_stations, :through => :licenses
> end
>
> class RadioStation
> has_many :licenses
> has_many :songs, :through => :licenses
> end
>
> class License
> belongs_to :radio_station
> belongs_to :song
> end
> =======
>
> Licenses are either active or not. Given a Song, we want to know which
> Licenses are active. If that information was on Song instead, we could
> just do something like:
>
> scope :licensed_for_radio_station, lambda { |rs|
> where(:licensed_stations => rs) }
>
> But we can't, since it's on License instead. So, two questions:
>
> 1.) Given a Song, we want to know which Licenses are active.
> What's the most idiomatic way to do this? Association method? Scope?
> etc.
> 2.) Given a Song and a RadioStation, what's the most idiomatic way
> to find the association that links them?
> 3.) Given a Song and a RadioStation, what's the most idiomatic way
> to modify the corresponding license to have :active => true?
>
> Any thoughts are appreciated. Thanks!
>
> ~ jf
>
Since licenses can either be active or deactive, I assume there is a
boolean field behind it, in which case a scope would be handy:
class License
belongs_to :radio_station
belongs_to :song
scope :activated, where => :active = true
end
This should allow you to perform the following:
song = Song.first
licences_for_song = song.licences.active
or even
licensed_stations = song.licences.activated.radio_stations
If you already have the radio station, finding of it is listed should be
easy:
licensed_stations.include? radio_station
The last issue is a little more complex, but I think something along the
lines of:
License.where(:song => song).where(:radio_station =>
radio_station).activate!
Then create a method to respond (I am assuming the combined keys are
unique):
class License
belongs_to :radio_station
belongs_to :song
scope :activated, where => :active = true
def activate!
update_attribute :active, true
end
end
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