     return (from, to)
   }
   
+  private func saveInvoice() -> Bool {
+    let invoice = Invoice()
+    invoice.number = numberField.stringValue
+    invoice.issueDate = issueDateField.dateValue
+    
+    
+    return true
+  }
+  
   // MARK: - IBAction
   
   @IBAction func cellValueChanged(sender: NSTextField) {

    
    itemsTable.setDelegate(self)
    itemsTable.setDataSource(self)
  }
  
  // MARK: - private
  
  private func addEmptyItem() {
    items.append(InvoiceItem())

  }
  
  @IBAction func save(sender: NSButton) {
    if saveInvoice() {
      closeWindow()
    }
  }
  
  @IBAction func cancel(sender: NSButton) {
