光滑的表查询:无法识别值 [英] Slick table Query: Trouble with recognizing values

问题描述

在这种情况下，谁能告诉我原因

Can anyone tell me why in this case:

Query(Users) foreach {case (userId, userName) =>       
    println(userId + ", " + userName) }

Scala可以识别userId，但在这种情况下:

Scala recognizes userId, but in this case:

val l = List[(Int, String)]()

Query(Users) foreach {
   case (userId, userName) =>
     l::(foo(List[(userId, userName)])) 
}

不是吗? (例如，在第二种情况下会识别"=>"右侧的userId，但在第一种情况下不会识别)

it doesnt? (as in, the userId on the right of the "=>" is recognized in the second case but not the first)

Users是一个光滑安装的数据库，如下所示:

Users is a slick-mounted database that looks like this:

object Users extends Table[(Int, String)]("Users") {

  def userId          = column[Int]("UserId", O.PrimaryKey, O.AutoInc)
  def userName        = column[String]("UserName")

  def * = userId ~ userName
}

推荐答案

我认为您的意思是:

l::(foo(List((userId, userName))))

将东西放在方括号之间时，您正在尝试键入列表，我假设您实际上是想将userId和userName的Tuple添加到列表中.

When you put stuff between the square brackets, you are attempting to type the list and I assume you actually wanted to add the Tuple of userId and userName to a List instead.

如果您只想将所有内容放入该List中，而又不需要该Tuple提取器，则也可以这样编写:

You could also write it like this if all you wanted to do was put it into that List and you did not need that Tuple extractor:

Query(Users) foreach { tup =>     
  l::(foo(List(tup))) 
}

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