Scala循环通过一个对象

Question

我通过这一行获得了一个对象:

val product_array:Option[Any] = scala.util.parsing.json.JSON.parseFull(products_json)

打印出来的对象如下所示:

(product1Id,Map(product_picture -> https://upload.wikimedia.org/wikipedia/commons/thumb/7/73/IPhone_3G.png/250px-IPhone_3G.png, product_price -> 299.99, recipient_picture -> https://www.allianz.com/static-resources/de/presse/mediendatenbank/people/v_1338807733000/zimerer_portrait_small_326x217.jpg, product_amount_gifted -> 100.00, recipient_username -> jDoe, product_name -> iPhone 3G, recipient_id -> 12345))(product2Id,Map(product_picture -> https://upload.wikimedia.org/wikipedia/en/thumb/7/7c/1stGen-iPad-HomeScreen.jpg/220px-1stGen-iPad-HomeScreen.jpg, product_price -> 399.99, recipient_picture -> https://image1.masterfile.com/em_w/05/11/94/400-05119409w.jpg, product_amount_gifted -> 200.00, recipient_username -> MJohnson, product_name -> iPad, recipient_id -> 67890)) 

如何循环遍历数组/对象以提取键和值？

更新:

当我尝试遍历对象时,它会将空值发送到键和值,如下所示:

for((key, value) <- product_array)     {       

}

这是原始的json:

{
   "product1Id":{
      "product_name":"iPhone 3G",
      "product_price":"299.99",
      "product_amount_gifted":"100.00",
      "product_picture":"https:\/\/upload.wikimedia.org\/wikipedia\/commons\/thumb\/7\/73\/IPhone_3G.png\/250px-IPhone_3G.png",
      "recipient_picture":"https:\/\/www.allianz.com\/static-resources\/de\/presse\/mediendatenbank\/people\/v_1338807733000\/zimerer_portrait_small_326x217.jpg",
      "recipient_username":"jDoe",
      "recipient_id":"12345"
   },
   "product2Id":{
      "product_name":"iPad",
      "product_price":"399.99",
      "product_amount_gifted":"200.00",
      "product_picture":"https:\/\/upload.wikimedia.org\/wikipedia\/en\/thumb\/7\/7c\/1stGen-iPad-HomeScreen.jpg\/220px-1stGen-iPad-HomeScreen.jpg",
      "recipient_picture":"https:\/\/image1.masterfile.com\/em_w\/05\/11\/94\/400-05119409w.jpg",
      "recipient_username":"MJohnson",
      "recipient_id":"67890"
   }
}

Answer 1

首先,请注意parseFull返回Option,这意味着您的第一步是检查它是否包含某些内容(例如,发生了解析错误),我建议您使用模式匹配:

products match {
  case Some(p) => println("Products found")
  case None => println("Error parsing JSON")
}

如果您的选项包含实际值,则它将被置于p变量中.接下来,请注意parseFull返回Option[Any],p也是Any如此.它应该在迭代之前进行转换:

p.asInstanceOf[Map[String,Map[String,Any]]]

现在你可以遍历地图,让我们使用for:

for {
  (id, desc) <- p.asInstanceOf[Map[String,Map[String,Any]]]
  (propName, propValue) <- desc
} println(propName + "=" + propValue)

它看起来像一个循环,但实际上它是一个双循环.它遍历外部地图,并进入每个内部地图.循环体里面,你可以访问id,desc,propName和propValue变量.这可能就是你要找的东西.

整个脚本:

import scala.util.parsing.json.JSON._

val json = """{"product1Id":{"..."recipient_id":"67890"}}"""

val products = parseFull(json)

products match {
  case Some(p) => 
    for {
      (id, desc) <- p.asInstanceOf[Map[String,Map[String,Any]]]
      (propName, propValue) <- desc
    } println(propName + "=" + propValue)

  case None => println("Error parsing JSON")
}

祝好运.