scala - spray-json can't find JsonReader for type List[T] -


i'm creating custom json readers case classes can't find implicit jsonreader type class list[t] used in other case class.

when checked defaultjsonprotocol, has implicit format collections already;

  implicit def listformat[t :jsonformat] = new rootjsonformat[list[t]] {     def write(list: list[t]) = jsarray(list.map(_.tojson).tovector)     def read(value: jsvalue): list[t] = value match {       case jsarray(elements) => elements.map(_.convertto[t])(collection.breakout)       case x => deserializationerror("expected list jsarray, got " + x)     }   }

here simplified code;

case class test(i: int, d: double) case class listoftest(t: list[test])  trait testresultformat extends defaultjsonprotocol {    import customformat._      implicit object testjsonformat extends rootjsonreader[test] {      override def read(json: jsvalue): test = {        val jsobject = json.asjsobject       val jsfields = jsobject.fields        val = jsfields.get("i").map(_.convertto[int]).getorelse(0)       val d = jsfields.get("d").map(_.convertto[double]).getorelse(0d)        test(i, d)     }   }    implicit object listoftestjsonformat extends rootjsonreader[listoftest] {      override def read(json: jsvalue): listoftest = {        val jsobject = json.asjsobject       val jsfields = jsobject.fields        val tests = jsfields.get("hs").map(_.convertto[list[test]]).getorelse(list.empty)        listoftest(tests)     }   }  }

here errors;

error:(230, 53) not enough arguments method convertto: (implicit evidence$1: spray.json.jsonreader[list[com.xx.test]])list[com.xx.test]. unspecified value parameter evidence$1.       val tests = jsfields.get("hs").map(_.convertto[list[test]]).getorelse(list.empty)                                                     ^ error:(230, 53) cannot find jsonreader or jsonformat type class list[com.xx.test]       val tests = jsfields.get("hs").map(_.convertto[list[test]]).getorelse(list.empty)                                                 ^

i think problem related fact jsonreader list[t] in defaultjsonprotocol rootjsonformat (not rootjsonreader), means can read , write it. so, when try read list[item], it's expected able write items. so, use rootjsonformat instead , throw exception in case try write (since don't support it). example:

import spray.json._  implicit object testjsonformat extends rootjsonformat[test] {    override def read(json: jsvalue): test = {      val jsobject = json.asjsobject     val jsfields = jsobject.fields      val = jsfields.get("i").map(_.convertto[int]).getorelse(0)     val d = jsfields.get("d").map(_.convertto[double]).getorelse(0d)      test(i, d)   }    override def write(obj: test): jsvalue = serializationerror("not supported") }

if aware of clean solution involving readers, please let me know because ran problem myself , couldn't find else.


-

Comments

Post a Comment

Popular posts from this blog

PySide and Qt Properties: Connecting signals from Python to QML -

i trying run simple pyside appliccation design made in qml. call function in qml python in separated thread. i have following qml view: import qt 4.7 rectangle { visible: true width: 100; height: 100 color: "lightgrey" text { id: datestr objectname: "datestr" x: 10 y: 10 text: "init text" font.pixelsize: 12 function updatedata(text) { datestr.text = qstr(text) console.log("you said: " + text) } } } here application: some imports.... #!/usr/bin/python import sys import time pyside import qtdeclarative, qtcore pyside.qtgui import qapplication pyside.qtdeclarative import qdeclarativeview the qthread worker.... #worker thread class worker(qtcore.qthread): updateprogress = qtcore.signal(int) def __init__(self, child): qtcore.qthread.__init__(self) self.child = child def run(self):
Read more

c# - DevExpress.Wpf.Grid.InfiniteGridSizeException was unhandled -

Image
when using devexpress, see error: devexpress.wpf.grid.infinitegridsizeexception unhandled message="by default, infinite grid height not allowed since grid rows rendered , hence grid work slowly. fix issue, should place grid container give finite height grid, or should manually specify grid's height or maxheight. note can avoid exception setting gridcontrol.allowinfinitegridsize static property true, in case grid run slowly." the problem dxgrid has infinite height. to fix, set height non-infinite. snoop absolutely invaluable this: if "height" xaml element infinite (i.e. 0 or nan ), can set using one of following: option 1: height="{binding path=actualheight, relativesource={relativesource mode=findancestor, ancestortype=uielement}}" option 2: verticalalignment="stretch" option 3: height="auto" hint: use verticalalignment="stretch" if child of grid <rowdefinition height=
Read more

scala - 'wrong top statement declaration' when using slick in IntelliJ -

Image
i'm porting project scala 2.9 2.10, therefore have use slick instead of scalaquery. i'm using slick 2.1.0 since supports ms access. according this tutorial , upgrade guide changed robs object class , added val robs : why error message wrong top statement declaration , how rid of it? edit: i'm new scala... according this question seems can't put val outside of methods or classes, right? code above directly in packge. right approach slick then? should move code in class or trait? according this changed val robs = tablequery[robs] to object robs extends tablequery(new robs(_)) {} . no warnings or errors anymore. :)
Read more