问题
I hava a Reads[T]. I would like to parse a Json object which is expected to be an array of T's. Is there a simple way to obtain a Reads[Seq[T]] without defining my Reads[T] as implicit? Essentially, I am looking for a function that takes Reads[T] and returns Reads[Seq[T]].
I came across Reads.TraversableReads, and thought that I can pass the implicit reader it needs explicitly, but this function also wants a CanBuildForm[...], which does not sound like fun.
回答1:
There is a method for this in the Reads companion object: Reads.seq. Its parameter is usually implicit, but you can always call it explicitly if you want:
val a: Reads[T] = ...
val b: Reads[Seq[T]] = Reads.seq(a)
来源：https://stackoverflow.com/questions/17597659/play-json-transforming-a-readst-to-readsseqt-without-implicits