JSON在播放框架（斯卡拉）硬编码值读取

Question

我想JSON隐含读取使用硬编码值，是这样的：

implicit val locationReads: Reads[Location] = (
    "I am a hardcoded value" and // something like that 
    (JsPath \ "lat").read[Double] and 
    (JsPath \ "long").read[Double] 
)(Location.apply _) 

有谁知道如何做到这一点？

Answer 1

使用Reads.pure产生Reads能产生一个恒定值。

implicit val locationReads: Reads[Location] = (
    Reads.pure("I am a hardcoded value") and 
    (JsPath \ "lat").read[Double] and 
    (JsPath \ "long").read[Double] 
)(Location.apply _) 

Answer 2

你可以做到这一点通过使用Location.apply自定义函数istead：

case class Location(s: String, lat: Double, lon: Double) 
object Location { 
    implicit val locationReads: Reads[Location] = (
     (JsPath \ "lat").read[Double] and 
     (JsPath \ "long").read[Double] 
    )((lat, lon) => Location("I am a hardcoded value", lat, lon)) 
}