I'm trying to provide a Scala wrapper API for a Java API that has fluent-style return types. Specifically, I want my Scala to rely on AnyVal instances as much as possible in order to reduce allocation.
I've found a simple solution which relaxes this fluent returns, but the problem is that WriteStream cannot return the type of the actual type of which it's being called, so would not be able to call AsyncFile methods after calling write.
An alternative solution requires a wrapper with a type class definition that is able to return the type of the object called, but I haven't managed to get it fully working. First of all, I can't seem to be able to get implicit variable to be picked and passed to write() method. Secondly, I don't think my implicit wrappers are correctly defined because I'd need a wrapper that takes a JavaWriteStream and the out is AsyncFile. So, seems like i'd need a wrapper for each possible combination of this implicit-based inheritance, and frankly, it looks way complicated for what it needs to do.
The idea of having WriteStream and AsyncFile separated is cos you have multiple classes inheriting (read: implicit conversions) from WriteStream, and this avoids the need to replicate each and every method of WriteStream in the other extending classes.
Finally, I'm also wondering if trying to adhere to this fluent-style is the best thing to do in the Scala world, or whether there's alternative ways to solve this problem in a more elegant way in the Scala world. Scala Future's andThen continuations comes to my mind as a better way to concatenate calls, but there's a single trait there.
Eventually figured out the code to make this work.