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POScala play json api: can't implicitly convert JsArray to JsValueWrapper
 

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  1. POScala play json api: can't implicitly convert JsArray to JsValueWrapper
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    <p>I have json rest api application based on play framework and want to receive information about validation errors when I parse incoming requests. Everything is working fine except conversion from json array to json value. Json structure I want to achieve: </p> <pre><code>{ "errors": { "name": ["invalid", "tooshort"], "email": ["invalid"] } } </code></pre> <p>When I tried to implement a sample it worked perfectly: </p> <pre><code>def error = Action { BadRequest(obj( "errors" -&gt; obj( "name" -&gt; arr("invalid", "tooshort"), "email" -&gt; arr("invalid") ) )) } </code></pre> <p>When I tried to extract the changing part like this:</p> <pre><code>def error = Action { val e = Seq("name" -&gt; arr("invalid", "tooshort"), "email" -&gt; arr("invalid")) // in real app it will be Seq[(JsPath, Seq[ValidationError])] BadRequest(obj( "errors" -&gt; obj(e: _*) )) } </code></pre> <p>I got a compiler error: </p> <blockquote> <p>type mismatch; found : Seq[(String, play.api.libs.json.JsArray)] required: Seq[(String, play.api.libs.json.Json.JsValueWrapper)]</p> </blockquote> <p>Maybe there is some implicit conversion I'm missing from JsArray to JsValueWrapper? But then, why does the sample works fine in the same file with the same imports?</p> <p>Play 2.1.1, Scala 2.10.0</p> <p><strong>UPDATE</strong>: Problem resolved thanks to Julien Lafont, the final code:</p> <pre><code>implicit val errorsWrites = new Writes[Seq[(JsPath, Seq[ValidationError])]] { /** * Maps validation result of Ember.js json request to json validation object, which Ember can understand and parse as DS.Model 'errors' field. * * @param errors errors collected after json validation * @return json in following format: * * { * "errors": { * "error1": ["message1", "message2", ...], * "error2": ["message3", "message4", ...], * ... * } * } */ def writes(errors: Seq[(JsPath, Seq[ValidationError])]) = { val mappedErrors = errors.map { e =&gt; val fieldName = e._1.toString().split("/").last // take only last part of the path, which contains real field name val messages = e._2.map(_.message) fieldName -&gt; messages } obj("errors" -&gt; toJson(mappedErrors.toMap)) // Ember requires root "errors" object } } </code></pre> <p>Usage:</p> <pre><code>def create = Action(parse.json) { // method in play controller request =&gt; fromJson(request.body) match { case JsSuccess(pet, path) =&gt; Ok(obj("pet" -&gt; Pets.create(pet))) case JsError(errors) =&gt; UnprocessableEntity(toJson(errors)) // Ember.js expects 422 error code in case of errors } } </code></pre>
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