PlayFramework 2.x - Forms / Associating error message to one element of a tuple - forms

Question

I've got this form mapping:
val myElement = Form(
mapping(
"title" -> nonEmptyText,
"schedule" ->
tuple("startSchedule" -> jodaDate("dd/MM/yyyy HH:mm"),
"endSchedule" -> jodaDate("dd/MM/yyyy HH:mm"))
.verifying(MyValidator().checkForEndScheduleConsistency("error.schedule")),
)(MyElement.apply)(MyElement.unapply)
)
MyElement class:
case class MyElement(title: String, schedule: (Datetime, Datetime))
MyValidator class:
def checkForEndScheduleConsistency(errorMsg: String) =
Constraint[(DateTime, DateTime)]("constraint.schedule", errorMsg) {
schedule =>
MyDomainValidator().checkForEndScheduleConsistency(schedule._1, schedule._2, Messages(errorMsg)) match {
case Success(s) => Valid
case Failure(f) => Invalid(ValidationError("custom error string from `f`"))
}
}
Requirement: An error message must be associated to the field schedule.endSchedule(tuple's element) if the schedule is inconsistent according to MyValidator object.
However, in order to have both required elements (startSchedule and endSchedule) available for checkForEndScheduleConsistency method, I can't apply a verifying method directly on the nested tuple's element named endSchedule. Instead, I have to apply one on the whole tuple in order to include startSchedule variable, as shown in the code snippet.
The drawback is that the error is not mapped to endSchedule but to schedule (that doesn't represent anything in my HTML form), and so nothing is displayed to screen when an inconsistent schedule appears.
Therefore, I have to use this "workaround" to achieve my requirement using Form's withError method:
def create = Action {
implicit request =>
myForm.bindFromRequest.fold(
myFormWithErrors => {
myFormWithErrors.error("schedule") match { //check for the presence of potential schedule error
case Some(e) => {
BadRequest(views.html.create_element("Create an element", myFormWithErrors.withError("schedule.endSchedule", Messages("error.schedule"))))
}
case _ => BadRequest(views.html.create_element("Create an element", myFormWithErrors))
}
},
myForm => {
treatSubmittedMyForm(myForm)
}
)
}
=> Very ugly and anti-DRY.
Is there a way to apply verifying on the tuple and despite of that, apply the error message to a nested tuple's element? In my case, on endSchedule.

Answer 1

Probably the best solution is to replace the default helpers provided by Play when rendering the field by one of your own making, as per documentation:
#(elements: helper.FieldElements)
<div class="#if(elements.hasErrors) {error}">
<label for="#elements.id">#elements.label</label>
<div class="input">
#elements.input
<span class="errors">#elements.errors.mkString(", ")</span>
<span class="help">#elements.infos.mkString(", ")</span>
</div>
</div>
That way you can manually replace the error reference to the right element. Not extremely nice but you should be able to create a reusable tag from it.

Answer 2

The best solution is to precise the global (to schedule) "error" key into the more specific generated input directly, here the schedule.endSchedule input:
#inputText(hobbyForm("schedule.endSchedule"), 'id -> "schedule.endSchedule", '_error -> hobbyForm.error("schedule")
Notice the part: '_error -> hobbyForm.error("schedule")