Hello everybody,
Still trying to learn how to use lift efficiently and effectively, I
got a little bit confused about the toForm function in the model/
mappers. Admittedly, my web framework background may be limited, but
this looked to me as if some view code snuck into the model space
there (I must admit that I do like how RoR tries to keep the models
fairly clean of both controller code and of view code).
For my first little project, I was going to encapsulate the HTML field
formatting into a separate class (similar to what RoR does, but making
use of the type system).
This is a very quick brain dump, not running code.
// The different field types, at a higher level than HTML
abstract class InputType
case class TextField extends InputType
case class DateField extends InputType
case class DateTimeField extends InputType
// Rendering hints that an form field formatter may use, could also be
called FormGenerator ...
abstract class RenderingHint
case class MinLength(l: Int) extends RenderingHint
case class MaxLength(l: Int) extends RenderingHint
// Input-type aware callback'ed formatter, from the model's perspective
trait InputTypeHandler {
def handleTextField(fieldID: String, presetValue: String,
renderingHints: RenderingHint*)
def handleDateField(fieldID: String, presetValue: Date,
renderingHints: RenderingHint*)
}
// A model class using the callback
class ModelClass {
object aField extends MappedString(this, 128) {
def inputTypeCallback(InputTypeHandler handler) {
// A reasonable default should/could be pushed upwards in the
type hierarchy
handler.handleTextField(fieldID, this.is, MaxLength(this.length))
}
}
}
This InputTypeHandler could be a nice spot to deal with validation
result formatting:
class AnInputFormatter(errors: List[FieldError]) extends
InputTypeHandler {
def handleTextField(fieldID: String, presetValue: String,
renderingHints: RenderingHint*) {
errors.filter(_._1 == fieldID).match {
case Nil => /* format field normally */
case xs => /* format as error, i.e. red background, error
messages right of field .... */
}
}
...
}
// A snippet
...
val inputFormatter = new AnInputFormatter(errorsFromValidation)
bind("form", html, "aField" -> aModelClass.aField.
inputTypeCallback(inputFormatter))
...
Maybe a partial function, potentially on case classes, is better? Many
options ...
I'm looking forward to any feedback.
Best,
Clemens
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