Using this just requires it to bring it in scope, e.g. with an import:
Some weeks ago a colleague asked me why the Scala compiler is so stupid not to apply a implicit conversion in the following case:
But how should the compiler now how to convert an Option[JodaDateTime] to Option[ThriftDateTime]? Yes, there is a map() method in Option, but this is just some kind of usual convention, and it would be really dangerous if the scala compiler would automatically use a method map() if present.
At this time I just suggested to explicitly map or use an implicit conversion on Option:
But this is really cumbersome and you have to do it also for lists or any other container type, even if they all have a common map method with the same semantic.
FunctorsIt turns out that there is a functional class which describes the above situation, they are called functors.
A functor is simply a trait which specifies to supply a map() method with adheres to the functor laws.
The above functor definition is directly taken from Scalaz 7.
Using it for an implicit "container" conversion of our two classes means:
With that the conversions work in all "containers" for which scalaz defines functors:
..and if you want you can write your own functors for your classes.