How to get the user input from the Spinner - Javafx - javafx

Question

I created a Spinner with JavaFx accepting Integer only. The user choose a number between 0 and 10 (number of turns he decides to rest ingame).
However, I want to get this value when the user clicks on the "OK" button.
Here is the line where I want to call the user input. (I tried .getValue() but it's not working) :
#Override
public void initialize(URL url, ResourceBundle rb) {
RestOK.setOnAction(e -> ToF.rest((int) RestSpinner.getValue(), restTime));
}
And this is the fxml :
<?xml version="1.0" encoding="UTF-8"?>
<?import javafx.scene.control.Button?>
<?import javafx.scene.control.Label?>
<?import javafx.scene.control.Separator?>
<?import javafx.scene.control.Spinner?>
<?import javafx.scene.control.SpinnerValueFactory.IntegerSpinnerValueFactory?>
<?import javafx.scene.layout.AnchorPane?>
<AnchorPane maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="200.0" prefWidth="400.0" xmlns="http://javafx.com/javafx/8.0.141" xmlns:fx="http://javafx.com/fxml/1" fx:controller="com.cc.view.RestController">
<children>
<Label layoutX="66.0" layoutY="46.0" text="How many turns do you need for resting?" />
<Separator layoutX="81.0" layoutY="83.0" prefWidth="240.0" />
<Spinner fx:id="RestSpinner" editable="true" layoutX="94.0" layoutY="109.0">
<valueFactory>
<SpinnerValueFactory.IntegerSpinnerValueFactory max="10" min="0" />
</valueFactory>
</Spinner>
<Button fx:id="RestCancel" cancelButton="true" layoutX="170.0" layoutY="160.0" mnemonicParsing="false" onAction="#closeRest" text="Cancel" />
<Button fx:id="RestOK" layoutX="276.0" layoutY="109.0" mnemonicParsing="false" text="OK" />
</children>
</AnchorPane>
Thank you