Scala instantiation of a class with curly braces - scala

Question

I am starting with Scala and with ScalaFX, I understand most of the code but I don't understand this code using for the examples in ScalaFx;
where instantiate an anonymous class follow it by curly braces, How this works???
object ScalaFXHelloWorld extends JFXApp {
stage = new PrimaryStage {
title = "ScalaFX Hello World"
scene = new Scene {
fill = Black
content = new HBox {
padding = Insets(20)
children = Seq(
new Text {
text = "Hello"
style = "-fx-font-size: 48pt"
fill = new LinearGradient(
endX = 0,
stops = Stops(PaleGreen, SeaGreen)
)
},
new Text {
text = "World!!!"
style = "-fx-font-size: 48pt"
fill = new LinearGradient(
endX = 0,
stops = Stops(Cyan, DodgerBlue)
)
effect = new DropShadow {
color = DodgerBlue
radius = 25
spread = 0.25
}
}
)
}
}
}
}
the part I don't understand is why in the creation of an anonymous class is follow by curly braces (with some more declarations)(Scene is not a trail to be filling the abstract parts of that class) and even fill or content are functions not a variables and Black for fill for instant is a val meaning that this line
fill = Black
is doing calling a function fill and assigning a val to it(don't make sense for me ), this is fill definition
def fill: ObjectProperty[jfxsp.Paint] = delegate.fillProperty
and this is Black
val Black = new Color(jfxsp.Color.BLACK)
how works this instantiation of a new object with curly braces please help, want to understand.
This is because ScalaFx is wrapping JavaFx and something special is going on here?.
Thank you guys.
Update:
Well now I know that it is calling a setter via syntax sugar however I check that setter and I don't understand what is going on there
Check it out:
def fill: ObjectProperty[jfxsp.Paint] = delegate.fillProperty
def fill_=(v: Paint) {
fill() = v
}
how come the setter is calling the getter to update the value?
delegate.fillProperty
is a function that return a value

Answer 1

The syntax for anonymous classes in Scala is borrowed from Java; you can see it here, too:
class Coder {
protected String name;
public Coder(String name) {this.name = name;}
}
public static void main(String[] args) {
// Prints "Mr. Noble"
new Coder("Noble") {
private String prefix = "Mr.";
{
System.out.println(prefix + " " + name);
}
}
}
Because Scala lets you write your constructor code in the class body, all of your x = y statements are executed when you instantiate those anonymous classes. As #resueman points out, these are actually getters and setters in this format:
class Scene {
var _fill
def fill_=(color: Color) // Setter, has some hidden logic to set up the UI
def fill = _fill // Getter
}
And your statement fill = Black is desugared to fill_=(Black).