     
     fileprivate func prepareForm() {
         
+        let visualizeValidationError: (TextCell, TextRow) -> ()  = { cell, row in
+            cell.contentView.layer.borderWidth = !row.isValid ? 2 : 0
+            cell.contentView.layer.borderColor = !row.isValid ? UIColor.red.cgColor : UIColor.clear.cgColor
+        }
+        
         self.form
             +++ Section("Server")
                 <<< TextRow() { row in

                    row.add(rule: RuleRequired())
                    row.validationOptions = .validatesOnChange
                }
            +++ Section("E-Mail")
                <<< TextRow() { row in
                    row.placeholder = "Enter e-mail address"

                    row.add(rule: RuleRequired())
                    row.validationOptions = .validatesOnChange
                }
                .cellUpdate { cell, row in
                    cell.contentView.layer.borderWidth = !row.isValid ? 2 : 0
                    cell.contentView.layer.borderColor = !row.isValid ? UIColor.red.cgColor : UIColor.clear.cgColor
                }
    }
    
    fileprivate func createBindings() {
