播放Json:在没有隐式的情况下将Reads [T]转换为Reads [Seq [T]] [英] Play Json: Transforming a Reads[T] to Reads[Seq[T]] without implicits

问题描述

我有一个Reads[T].我想解析一个Json对象，该对象应该是T的数组.是否有一种简单的方法来获取没有定义我的Reads[T]为隐式的Reads[Seq[T]] ?本质上，我正在寻找一个使用Reads[T]并返回Reads[Seq[T]]的函数.

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]].

我遇到了Reads.TraversableReads，并认为我可以显式地传递它需要的隐式阅读器，但是此功能还需要一个CanBuildForm[...]，听起来并不有趣.

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.

推荐答案

在Reads随播对象Reads.seq中有一种用于此目的的方法.它的参数通常是隐式的，但是如果需要，您始终可以显式调用它:

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)

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