Play (Scala) form validation error - validation

Question

I want to make a form validation in Play (Scala), I have done this several times but this time it shows error.. The error says:
Overloaded method value [apply] cannot be applied to
(play.api.data.Mapping[models.PIdetail])
Model:
package models
import java.util.Date
import play.api.libs.json._
import play.api.libs.functional.syntax._
import anorm._
import anorm.SqlParser._
import play.api.db.DB
import play.api.Play.current
import models._
case class Purchase_Invoice(supplier_id: String, paid_to_num: String, staff_id: String, paid_to_name: String, staff_name: String, paid_to_addr: String, PI_date: Date, PI_due_date: Date, payment: String, purchase_invoice_items: List[PIdetail], other: String, additional_note: String, terms_and_cond: String)
case class PIdetail(RI_id: Int, PO_id: String, product_id: String, description: String, qty: Int, total: String)
case class RIheader_PI(id_counter: Long, date_RI: Date, staff_id: String, status: Int)
Controller:
package controllers
import play.api._
import play.api.Logger
import play.api.mvc._
import play.api.data._
import play.api.data.Forms._
import play.api.data.format.Formats._
import play.api.mvc.Flash
import play.api.libs.json.Json
import play.api.libs.json._
import models._
object PurchaseInvoices extends Controller {
val submitPIForm = Form(
mapping(
"supplier_id" -> text,
"paid_to_num" -> text,
"staff_id" -> text,
"paid_to_name" -> text,
"staff_name" -> text,
"paid_to_addr" -> text,
"PI_date" -> date,
"PI_due_date" -> date,
"payment" -> text,
"purchase_invoice_items" -> list(
mapping(
"RI_id" -> number,
"PO_id" -> text,
"product_id" -> text,
"description" -> text,
"qty" -> number,
"total" -> text
)(PIdetail.apply)(PIdetail.unapply)
),
"other" -> text,
"additional_note" -> text,
"terms_and_cond" -> text
)(Purchase_Invoice.apply)(Purchase_Invoice.unapply)
)
...................... Some codes
...................... Some codes
}
really need your help guys.. thanks before.. ^^

Answer 1

Found out the error by myself.. ^^
It's because I have def list = TODO in my Controller..
So make sure you don't define a function/variable that has the same name with scala function..
Sorry to bother you guys... thx.. ^^