The approach I take to decompose JSON data delivered by JsonHandler
(which is in the form of Map[String, _]) is to use extractors that act
as converters, so that the code looks pretty much like in Joni's first
posting.
for{param <- json
("messageId", IsInt(messageId)) <- param}
yield ...
object IsInt {
def unapply(a: String): Option[Int] = try { Some(a.toInt) } catch
{ case _ => None }
}
You can set up nice extractors for all kind of types or to
automatically urldecode or check strings for being not empty and so
on.
-Chris
On 4 Mrz., 21:52, Joni Freeman <[email protected]> wrote:
> Tried it myself and that version does not work. You probably need
> nested for-comprehension which parses the JSON:
>
> for {
> user <- WorkerMgr.find(UserId(user)) ?~ "User not found"
> json <- r.json
> data <- Box(for {
> JField("messageId", JInt(messageId)) <- json
> JField("timestamp", JInt(timemillis)) <- json
> } yield (messageId, timemillis))
>
> } yield ...
>
> Cheers Joni
>
> On Mar 4, 9:55 pm, Joni Freeman <[email protected]> wrote:
>
>
>
> > Hi David,
>
> > Does this work?
>
> > for {
> > user <- WorkerMgr.find(UserId(user)) ?~ "User not found"
> > json <- r.json
> > JField("messageId", JInt(messageId)) <- json
> > JField("timestamp", JInt(timemillis)) <- json
> > } yield ..
>
> > Cheers Joni
>
> > On Mar 4, 9:28 pm, David Pollak <[email protected]> wrote:
>
> > > Folks,
>
> > > I'm working on parsing through some JSON that's posted/put as part of a
> > > request. I'd like to find the messageId field and only get it if its type
> > > is JInt. I'm doing this within a for comprehension that has a Box at the
> > > top of it, so the resulting expression must play well with Box. What I've
> > > got is:
>
> > > for {
> > > user <- WorkerMgr.find(UserId(user)) ?~ "User not found"
> > > json <- r.json
> > > (_, messageJson) <- (json \ classOf[JField]).find(_._1 ==
> > > "messageId")
> > > messageId <- Box.asA[JInt](messageJson)
> > > (_, timemillisJson) <- (json \ classOf[JField]).find(_._1 ==
> > > "timestamp")
> > > timemillis <- Box.asA[JInt](timemillisJson)
> > > } yield ...
>
> > > The lines that look for messageId and timestamp and insure they are JInts
> > > are kinda verbose. Is there a better way to do what I'm trying to do?
>
> > > Thanks,
>
> > > David
>
> > > --
> > > Lift, the simply functional web frameworkhttp://liftweb.net
> > > Beginning Scalahttp://www.apress.com/book/view/1430219890
> > > Follow me:http://twitter.com/dpp
> > > Surf the harmonics
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