类型列表采用类型参数(播放中的编译错误)

Question

目前正在学习 RESTFUL API 的基础知识，使用 Play，并遇到问题：我遵循一些长期教程，并认为正确的 scala 语法失败了！ 需要帮助，谢谢 这是错误的屏幕截图

package controllers
import play.api.libs.json.Json
import javax.inject.Inject
import play.api.Configuration
import play.api.mvc.{AbstractController, ControllerComponents}
import scala.concurrent.ExecutionContext

class PlacesController @Inject()(cc: ControllerComponents)(implicit assetsFinder: AssetsFinder, ec: ExecutionContext, configuration: Configuration)
extends AbstractController(cc) {

case class PlacesController(id: Int, name: String)
val thePlaces: List = List(
thePlaces(1, "newyork"),
thePlaces(2, "chicago"),
thePlaces(3, "capetown")
)
implicit val thePlacesWrites = Json.writes[PlacesController]
def listPlaces = Action {
val json = Json.toJson(thePlaces)
Ok(json)
}}

Answer 1

你的代码有很多问题。您正在定义thePlaces，同时在定义的右侧调用thePlaces本身。

此外，您的命名令人困惑。

试试这个：

final case class Place(id: Int, name: String)
object Place {
implicit val placeWrites = Json.writes[Place]
}
class PlacesController ... {
val thePlaces: List[Place] = List(
Place(1, "newyork"),
Place(2, "chicago"),
Place(3, "capetown")
)
def listPlaces = Action {
val json = Json.toJson(thePlaces)
Ok(json)
}
}

Answer 2

终于得到了答案，希望这对将来对其他人有所帮助！！

class PlacesController @Inject()(cc: ControllerComponents)(implicit assetsFinder: AssetsFinder, ec: ExecutionContext, configuration: Configuration)
extends AbstractController(cc) {

case class PlacesController(id: Int, name: String)
val thePlaces: List[(Int, String)] = List(
(1, "newyork"),
(2, "chicago"),
(3, "capetown")
)
implicit val thePlacesWrites = Json.writes[PlacesController]
def listPlaces = Action {
val json = Json.toJson(thePlaces)
Ok(json)
}

}