Anorm中“对重载定义的歧义引用”的含义

Question

我最近开始学习Scala和Play框架，在阅读Play框架的Anorm文档时，我得到了以下代码片段：

import anorm.SqlParser.str

val id: List[String] = 
  SQL("insert into City(name, country) values ({name}, {country})")
 .on('name -> "Cambridge", 'country -> "New Zealand")
 .executeInsert(str.+) // insertion returns a list of at least one string keys

却被编译错误卡住了：

package controllers
import play.api.Play.current
import javax.inject._
import play.api._
import play.api.mvc._
import play.api.db.{ Database, NamedDatabase, DB }
import anorm._
import anorm.SqlParser.str

@Singleton
class HomeController @Inject()() extends Controller { 

  def index = Action {
   DB.withConnection { implicit c =>
     val id: List[String] = 
       SQL("insert into City(name, country) values ({name}, {country})")
       .on('name -> "Cambridge", 'country -> "New Zealand")
       .executeInsert(str.+) // insertion returns a list of at least one string keys  
     Ok("Result is: " + id)
   }       
  }

}

libraryDependencies ++= Seq(
  jdbc,
  cache,
  ws,
  "org.scalatestplus.play" %% "scalatestplus-play" % "1.5.1" % Test,
  "com.typesafe.play" %% "anorm" % "2.5.0",
  "org.postgresql"     %  "postgresql" % "9.3-1102-jdbc41"
)

Answer 1

您没有使用.str，必须使用列位置或列名调用该列，以便将如此引用的列解析为字符串。