How to test an empty value of a json

[Corey Nolet]

So I have the following json:

{ people: [ { id: "1", name: "bill" }, { id: "2" }] }

What I want to do is write a quick inline filter do grab me a list of all the people who have a name. I'm trying to do this:

val json = JsonBuffer.parse(jsonString)
val peopleWithNames = json.people.as[List[Json]].filter(_.name != null)

I'm assuming since it seems you are following Martin Odersky's scala semantics pretty closely that you have opted out of using null. I've tried using None and i still can't seem to get the properly.

I see a normalizeOrEmpty() method. Do I need to call that on anything that I think could be empty?

[Jon Pretty]

Hi Corey,

Don't use the `normalize` methods. I think you'd be best off doing the following, in 0.9.0, though it's not ideal. I've highlighted the changes in red.

// We're going to explicitly specify the return types from now on

// using a different "strategy". This was renamed to "modes.explicit"

// in v1.0.0.

import strategy.explicit

// Remember to call `.get` on the parse method now

val json = JsonBuffer.parse(jsonString).get

// and also on the first `as` method

val peopleWithNames = json.people.as[List[Json]].get.filter(_.name.as[String].opt.isDefined)

To do the same thing in v1.0.8, you'd write:

val json = JsonBuffer.parse(jsonString)

val people = json.people.as[List[Json]].filter(_.name.as[Option[String]].isDefined)

Hope that helps!

Jon

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Jon Pretty | @propensive

[Corey Nolet]

I'm using 1.0.8 at home just to test.

    val json  = Json.parse("{ \"people\":[{ \"id\":1, \"name\":\"Corey\"}, { \"id\":2}]}")

    val jsonbuffer = JsonBuffer.empty

    jsonbuffer.people = json.people

    jsonbuffer.people = jsonbuffer.people.as[List[Json]].filter(it => {

      it.name.as[Option[String]].isDefined

    })

This code throws this exception:

Exception in thread "main" rapture.data.MissingValueException: Missing value: <value>.name

at rapture.data.DataType$$anonfun$doNormalize$1$$anonfun$apply$2.liftedTree2$1(data.scala:113)

at rapture.data.DataType$$anonfun$doNormalize$1$$anonfun$apply$2.apply(data.scala:108)

at rapture.data.DataType$$anonfun$doNormalize$1$$anonfun$apply$2.apply(data.scala:103)

at rapture.core.package$$anonfun$yCombinator$1.apply(package.scala:46)

at rapture.data.DataType$class.doNormalize(data.scala:121)

at rapture.json.Json.doNormalize(json.scala:86)

at rapture.data.DataType$class.$normalize(data.scala:92)

at rapture.json.Json.$normalize(json.scala:86)

at rapture.data.DataType$$anonfun$as$1.apply(data.scala:126)

at rapture.core.modes$ThrowExceptions.wrap(modes.scala:105)

at rapture.data.DataType$class.as(data.scala:125)

at rapture.json.Json.as(json.scala:86)

at cjn.RaptureJson$$anonfun$main$1.apply(RaptureJson.scala:18)

at cjn.RaptureJson$$anonfun$main$1.apply(RaptureJson.scala:17)

at scala.collection.TraversableLike$$anonfun$filter$1.apply(TraversableLike.scala:264)

at scala.collection.immutable.List.foreach(List.scala:318)

at scala.collection.TraversableLike$class.filter(TraversableLike.scala:263)

at scala.collection.AbstractTraversable.filter(Traversable.scala:105)

at cjn.RaptureJson$.main(RaptureJson.scala:17)

at cjn.RaptureJson.main(RaptureJson.scala)

[Jon Pretty]

Hi Corey,

Sorry for taking a bit longer this time!

That's actually a bug -- it's exactly what getting `.as[Option[T]]` is designed to avoid! Sorry...

It's quite a recent one, and something I'm looking to fix as soon as I can. It's being tracked here:

  https://github.com/propensive/rapture-json/issues/23

If you watch the ticket on Github, you should expect to see it fixed in the next couple of days. Sorry about that...

Cheers,
Jon

[Jim Newsham]

Hi guys,

I'm using rapture-json 1.1.0 with json4s 3.2.11, and I am seeing the same behavior that issue #23 claims to have fixed.  Test code:

import rapture.json._

import rapture.json.Json

import rapture.json.jsonBackends.json4s._

object TestRaptureJsonOption extends App {

    val json = json"""{ "foo": "bar" }"""

    println(json.missing.as[Option[String]])

  

}

Exception:

Exception in thread "main" rapture.data.MissingValueException: Missing value: <value>.missing

at rapture.data.DataType$$anonfun$doNormalize$1$$anonfun$apply$2.liftedTree2$1(data.scala:113)

at rapture.data.DataType$$anonfun$doNormalize$1$$anonfun$apply$2.apply(data.scala:108)

at rapture.data.DataType$$anonfun$doNormalize$1$$anonfun$apply$2.apply(data.scala:103)

at rapture.core.package$$anonfun$yCombinator$1.apply(package.scala:41)

at rapture.data.DataType$class.doNormalize(data.scala:121)

at rapture.json.Json.doNormalize(json.scala:131)

at rapture.data.DataType$class.$normalize(data.scala:92)

at rapture.json.Json.$normalize(json.scala:131)

at rapture.data.DataType$$anonfun$as$1.apply(data.scala:126)

at rapture.core.internal.ThrowExceptionsMode.wrap(modes.scala:175)

at rapture.data.DataType$class.as(data.scala:125)

at rapture.json.Json.as(json.scala:131)

at TestRaptureJsonOption$.delayedEndpoint$TestRaptureJsonOption$1(TestRaptureJsonOption.scala:8)

at TestRaptureJsonOption$delayedInit$body.apply(TestRaptureJsonOption.scala:5)

at scala.Function0$class.apply$mcV$sp(Function0.scala:40)

at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)

at scala.App$$anonfun$main$1.apply(App.scala:76)

at scala.App$$anonfun$main$1.apply(App.scala:76)

at scala.collection.immutable.List.foreach(List.scala:381)

at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:35)

at scala.App$class.main(App.scala:76)

at TestRaptureJsonOption$.main(TestRaptureJsonOption.scala:5)

at TestRaptureJsonOption.main(TestRaptureJsonOption.scala)

Any ideas?  Thanks,

Jim

[Jon Pretty]

Hi Jim,

Sorry for the delay in responding - I've been distracted by a conference the last few days, and I'm just catching up...

Yes, I thought this issue was fixed for all backends, but evidently it's not. I've got plans to reimplement the code where this is failing (for different reasons) before my talk at Scala Days in two weeks, but hopefully I'll be able to commit and release a working version in a week or so.

I've just added a test to the test suite, which ought to be identical to the example you sent, it appears to work with the latest source version, so I've possibly fixed it in another patch.

I'll spend more time investigating over the next week, but for now, I've reopened the issue.

Cheers,
Jon

[Jim Newsham]

No problem, thanks for the response.  Easy enough to work around in the meantime (by using a simple extractor utility method which catches the exception and returns an option).

Regards,

Jim

[Jon Pretty]

Thanks, Jim,

An alternative is to use a different mode for the optional calls. If you include this import:

  import rapture.core.modes.returnOption._

then all calls to the `as` method will be returned as `Option`s of what they would otherwise be. It's cumbersome if you're continually switching between modes just to get `Option`s out, but if you always want `Option`s, then this should be by far the best way.

To get back to the "normal" mode, just

  import rapture.core.modes.throwExceptions._

Any use?
Jon