问题描述
def toFun()(implicit a: Box) = a.toCircle()
根据我的理解，目前，我们需要这样的语法：
anObject match {
case Another(a,b,c,_) =>
implicit val tempA = a
toFun()
case YetAnother(a,_) =>
implicit val tempA = a
toFun()
}
我们有更直观的语法吗？
anObject match {
case Another(implicit a,_) =>
toFun()
case YetAnother(implicit a,_) =>
toFun()
}
更新：
我知道我们可以这样做：
anObject match {
case Another(a,_) =>
toFun()(a)
case YetAnother(a,_) =>
toFun()(a)
}
但是对于像这样的方法：
def toFun()(implicit a: Box,b: Size,c: Context) = a.toCircle()
需要执行以下操作，从而违背了隐式的目的：
def main = {
implicit context =>
anObject match {
case Another(a,_) =>
toFun()(a,context)
case YetAnother(a,context)
}
}
示例：
请注意 messageContext 及其用法
class Worker extends Actor {
def receive = {
case m: MessageContext =>
/**
*
* Notice this
*/
implicit val messageContext = m
processor.processMessage{
conversation =>
val lastMessage = conversation.chat.last
lastMessage.message match {
case Some(text) =>
if (text.contains("/search")) {
val searchArgs = text.trim.split("/search")
if (searchArgs.nonEmpty) {
val query = searchArgs.last.trim
system.scheduler.scheduleOnce(1800 milliseconds) {
val activeContent = s"""
Some content"
|""".stripMargin)
conversation.activeContent = activeContent
processor.reply(s"""
|Here are search results for "${query}":
|${activeContent.mkString("\n------------\n")}
|
|""".stripMargin)
}
s"""Hello ${conversation.user.firstName},we have received a search query for "${query}". We will soon respond with search results"""
} else {
s"""Hello ${conversation.user.firstName},please enter a keyword post search command,i.e. "/search keyword"!"""
}
} else if (text.contains("/remind")) {
if (conversation.activeContent.isEmpty) {
"Please /search something first"
} else {
val remindArgs = (allCatch opt(text.split("/remind").last.trim.toInt)) // .split(" ")
if (remindArgs.isDefined) {
system.scheduler.scheduleOnce(5000 milliseconds) {
/**
*
* The above implicit is used here,if I pass it as an argument,then I will needed to pass other implciit arguments as well
* If I pass message as a standard argument,then the reply method looses it's simplciity,and please do factor in that
* we will need to call it at n number of times as the conversation tree grows
*/
processor.reply(s"""Here's the reminder after 5 seconds for resource: ${conversation.activeContent(remindArgs.get - 1)}""")
}
s"Hello ${conversation.user.firstName},we would love to remind you about the resource: ${conversation.activeContent(remindArgs.get - 1)} "
} else {
"""Please enter valid index number,refer to search results. Use the number in begining of each search result item i.e. "/remind 1" or "/remind 2" or "/remind 5"!"""
}
}
} else {
conversation.activetopic match {
case Some(topic)=>
topic match {
case Goal =>
"Some message..."
case Changetopic =>
if (List("yes","yeah","yo","yay","y","ya","yepp","why not").contains(text.toLowerCase.replace("!",""))) {
system.scheduler.scheduleOnce(5000 milliseconds) {
/**
*
* Notice this
*
*/
processor.reply(s"""Yeah,we can change the topic""")
}
"Let me think if we are done here"
}
else {
"Some message..."
}
case .......
}
case _ => s"No active topic out there! Would you like to /start again?"
}
}
case None =>
conversation.activetopic match {
case Some(topic)=>
topic match {
case GoalUploadPrompt =>
lastMessage.raw.document match {
case Some(doc) => doc.toString
case None => lastMessage.raw.photo match {
case Some(photo) =>
"Some message..."
case None => "Some message..."
}
}
case _ =>
"Some message..."
}
case None => "Some message...."
}
}
}(m,ws,token)
case _ =>
}
}
object processor {
def processMessage(cb: (BotConversation) => String)(implicit msg: MessageContext,ws: WSClient,token: String) = ?
}
解决方法
如评论中所述，您始终可以显式传递隐式参数。 这是一种可能性。
或者，先设置隐式，然后调用：
implicit val (a,b) = foo match {
case Something(a,b,_) => a -> b
case Another(a,_) => a -> b
}
toFun()
或者，为了解决评论中提出的另一种可能性：
case foo match {
case DoNothing =>
case _ =>
implicit val (a,b) = foo match {
case Something(a,_) => a -> b
case Another(a,_) => a -> b
}
toFun()
}
一般来说，您可以不断提出额外的复杂性，但在某些时候应该会变得很明显，如果您必须跳过这么多圈子以隐式提供您的值，那么也许，它们不应该真的首先是隐含的？