scala - 不在 Controller 的方法中使用 head on list

Question

我有以下 Controller 方法:

  def edit(bookId: Int): Action[AnyContent] = messagesAction {implicit request => {
    val books = Book.getBookId(bookId)
    if(books.nonEmpty) Ok(views.html.book.create(bookForm.fill(books.head)))
    else NotFound("Book is not found.")
  }}

但我对自己的做法并不满意。

实际上，我不想测试列表(书籍 val)的空性。

我试过类似的东西:

  def edit2(bookId: Int): Action[AnyContent] = messagesAction {implicit request => {
    Book.getBookId(bookId).foreach(book => Ok(views.html.book.create(bookForm.fill(book))))
    NotFound("Book is not found.")
  }}

它确实可以编译，但我每次都有 NOtFound 重定向。

我怎么能这样做？

Answer 1

也许您只是在寻找模式匹配？

Book.getBookId(bookId) match {
   //get head of list and ignore rest
   case book :: _ => Ok(views.html.book.create(bookForm.fill(book)))
   //if list is empty return not found 
   case Nil       => NotFound("Book is not found.")
}