在scala \ Play中解析Json数组响应 [英] Parse Json array response in scala\Play

问题描述

有一个Web服务返回一些东西

There is a web service returning array of something

{"apps": [{"name": "one"}, {"name": "two"}]}

在我的代码中，我想遍历每个名​​字

In my code I want to iterate every name

val request = WS.url(s"http://localhost:9000/getData")

val json = request.get.map { response =>
  (response.json \ "apps" \\ "name")
}

json.foreach(println)

但是我所有的尝试都返回单条记录

However all my attempts return single record

// Expect
one
two
// Actual
ListBuffer("one", "two")

推荐答案

首先，这里的整洁解决方案是:

First of all, the neat solution here would be:

val request = WS.url(s"http://localhost:9000/getData")

request.get.map { response =>
  val names = (response.json \ "apps" \\ "name")
  names.foreach(println)
}

第二，如果您不想对类型感到困惑，则应更改命名标准.对于Future对象，可以以前缀future开头，对于Option，可以以maybe开头，依此类推.如果这样做，示例中的问题将更加明显:

Secondly, if you don't want to get confused about the types, you should change your naming standards. For a Future object, you may start with the prefix future, for an Option, it could start with maybe, etc. If you do so, the problem in your example will be more obvious:

val request = WS.url(s"http://localhost:9000/getData")

val futureJson = request.get.map { response =>
  (response.json \ "apps" \\ "name")
}

futureJson.foreach(println) // you call foreach for a Future, not for a List

第三，为什么Future特征具有一个称为foreach的方法?我认为这对于初学者甚至中级开发人员都感到困惑.从其他语言中我们知道，foreach意味着迭代对象列表.在Scala中，它被视为单子运算"的一部分，对我来说，这仍然是一个灰色区域:)，但是Scala源中对Future.foreach的注释是这样的:

Thirdly, why would Future trait have a method called foreach? I think that's confusing for beginners and even mid-level developers. We know from other languages that, foreach means iterate over a list of objects. In Scala, it is considered part of "Monadic operations" which is still a gray area for me :), but the comment for Future.foreach in Scala source is this:

  /** Asynchronously processes the value in the future once the value becomes available.
   *
   *  Will not be called if the future fails.
   */
  def foreach[U]

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