Scala: Adding logging around a repository
We wanted to add some logging around one of our repositories to track how many times users were trying to do various things on the application and came across a cool blog post explaining how we might be able to do this.
We ended up with the following code:
class BarRepository { def all: Seq[Bar] = Seq() def find(barId:String) : Bar = Bar("myBar") }
class TrackService(barRepository:BarRepository) { def all : Seq[Bar] = { var bars = barRepository.all; println("tracking all bars"); bars } }
implicit def trackServiceToBarRepository(t:TrackService) : BarRepository = t.barRepository
We can then use it like this:
scala> val service = new TrackService(new BarRepository()) service: TrackService = TrackService@4e5394c scala> service.all tracking all bars res6: Seq[Bar] = List()
If a method doesn’t exist on TrackService then the implicit conversion ensures that the appropriate method will be called on BarRepository directly:
scala> service.find("mark") res7: Bar = Bar(myBar)
I came across another way to achieve the same results by making use of traits although we’d need to change our design a little bit to achieve this pattern:
trait IProvideBars { def all : Seq[Bar] def find(barId:String) : Bar }
class BarRepository extends IProvideBars { def all: Seq[Bar] = Seq() def find(barId:String) : Bar = Bar("myBar") }
trait Tracking extends IProvideBars { abstract override def all : Seq[Bar] = { val bars = super.all; println("tracking all bars"); bars } }
scala> val b = new BarRepository() with Tracking b: BarRepository with Tracking = $anon$1@ddc652f scala> b.all tracking all bars res8: Seq[Bar] = List()
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http://www.mydiscoutlet.com CD Duplication
