Only bind part of the Form mappings from request - scala

Question

I am using Play 2.1.2 and I have a Form with the following mapping:
Form(
mapping(
"id" -> ignored(NotAssigned: Pk[Long]),
"name" -> nonEmptyText,
"stock" -> number(min = 0),
"initialAmount" -> number(min = 0),
"distUnitId" -> longNumber,
"categoryId" -> longNumber
)
(BarItem.apply)
(BarItem.unapply)
)
In the view, I want to use a form helper to edit only part of the values. In particular, the "initialAmount" value is meant to be only set once - when creating an item - and not be allowed to change on edit. So I just do not want to display it in the form and "keep" its previous value after form submission.
Currently the interesting part of the edit view looks like this:
#form(routes.Application.update(id), 'class -> "form-inline") {
<fieldset>
#inputText(barItemEditForm("name"), '_label -> "Produktbezeichnung")
#inputText(barItemEditForm("stock"), '_label -> "Lagermenge")
#select(
barItemEditForm("distUnitId"),
distUnits,
'_label -> "Einheit"
)
#select(
barItemEditForm("categoryId"),
categories,
'_label -> "Kategorie"
)
When navigating to the edit view, I fill the form with the fill() method of the Form class:
BarItem.findById(id).map {
item =>
Ok(html.edit(id, barItemEditForm.fill(item), DistUnit.selectOptions, Category.selectOptions))
}.getOrElse(NotFound)
In the action, that handles the form submission I bind the Form from request like so:
...
implicit request =>
barItemEditForm.bindFromRequest.fold(
formWithErrors => BadRequest(html.edit(id, formWithErrors, DistUnit.selectOptions, Category.selectOptions)),
item => {
...updateStuff...
}
)
...
So the problem is now, that as I do not have an input field for "initialAmount" in the view, I get an error when binding from request, saying it has no value.
Is it somehow possible to only apply part of the values from request and keep this one value from the call to fill() before?
Or can anyone suggest a proper way to handle this kind of "partial editing"?
I'm really looking forward to any suggestions!

Answer 1

Since you want to keep the value, that probably means a hidden input when you rerender the form. If the previous value comes from elsewhere, e.g. the database, you could define another form with an ignored mapping for that field.