scala - dispatch example not working

Question

I'm following the very first example in the dispatchdocs -

    val svc = url("http://api.hostip.info/country.php")
    val country = Http(svc OK as.String)
    for (c <- country)
      println(c)

I do not get any output printed. When I change it to below to make blocking call then I get the output.

val res = country()
println(res)

Need help with this.

Full program-

import dispatch._
object DispatchTest {

  def main(args: Array[String]) {
    val svc = url("http://api.hostip.info/country.php")
    val country = Http(svc OK as.String)
    for (c <- country)
      println(c)
  }
}

I don't think is blocking.. res is still a Future no ? try println(res.get) — twillouer, Feb 07 '13 at 11:19
to me it works perfectly as is... and it should, because the `for` comprehension wraps the `println` command in the `Promise` object, so it will be executed only when the `c` value is available — pagoda_5b, Feb 07 '13 at 11:31
what version of dispatch are you using? can you show your build.sbt or whatever? — pagoda_5b, Feb 07 '13 at 11:38
Anyway it looks to me like a question more appropriate to the [dispatch mailing list](https://groups.google.com/forum/?pli=1#!forum/dispatch-scala) — pagoda_5b, Feb 07 '13 at 11:39

score 6 · Accepted Answer · answered Feb 07 '13 at 11:40

6

Hmm, not sure here, but maybe the problem is that your main thread is finished so fast, that background thread (in which Dispatch works asynchronously) has no time for taking action?

To check this you may try to insert a delay:

for (c <- country) // Here we spawn a background thread!
  println(c)

Thread.sleep(500) // So let's wait half a second for it to work

Of course, in real program you should never need to do this.

Another option for delay is simply a readLine() in the end of main.

answered Feb 07 '13 at 11:40

NIA

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you can also check if your code works, when you paste it in the sbt-console – pagoda_5b Feb 07 '13 at 11:43
Yes this is the case. I get the output when I add the delay. Thanks! – Shwetanka Feb 07 '13 at 11:55
you might need to increase the delay in case your connection is very slow. – AnonGeek Jun 09 '13 at 18:21

score 0 · Answer 2 · answered Feb 07 '13 at 11:27

It works here:

scala> import dispatch._
import dispatch._

scala> val svc = url("http://api.hostip.info/country.php")
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
svc: com.ning.http.client.RequestBuilder = com.ning.http.client.RequestBuilder@2f823290

scala> val country = Http(svc OK as.String)
country: dispatch.Promise[String] = Promise(-incomplete-)

scala> for (c <- country)
     |   println(c)

scala> BR

Note that BR which appeared after the prompt.

Are you sure the country wasn't printed somewhere but you didn't notice because it was mixed up with other output?

I'm running it as a main function. I have updated my question. — Shwetanka, Feb 07 '13 at 11:31

scala - dispatch example not working

2 Answers2