Creating nodes in execution time

Question

I'm trying to create a node in response to certain events, like that:
Stage {
    title: "Application title"
    scene: Scene {
        width: 500, height: 200
        content: [
            Button {
                text: "Button"
                action: function() {
                    Circle {
                        radius: 40
                        fill: Color.BLACK
}But the circle doesn't appear, because I guess the circle needs to link to the scene, isn't it?
Then, do I need to indicate in the scene all the posibles nodes that it can be exist??
I'm a little confused about this thing. I'll appreciate any help. :)

Answer 1

As JavaFX is translated to Java and doesn't have primitive types, which are the only value types in Java platform, thus leaving only the reference types, we can assume FX variables hold a reference to the object and not the object itself (as any Java class variable).
When two or more variables are binded, they will always share the same reference. It looks like a compiler "trick", the binded variables become aliases to a common variable which actually holds the reference to the real object. Simillar to the C++ references, declared by putting an ampersand (&) before the variable name.
Botton line is that the objects themselves are not copied because it would be computationally very expensive. But also I can't accurately answer your question because there are several algorithms for heap management and several bytecodes translations for a single chunk of JavaFx source code
I can only tell you what happens in language semantics, as for memory usage and CPU usage it will depend on the implementation and even on the device.
The performance and memory usage differences between the approaches in the three examples provided is negligible. What affects the performance is the number of nodes, the depth level of the content tree and also the management algorithm that each container use.
But using containers is very useful because they can efficiently handle resizing and positioning of the nodes thus improving aesthetics, decreasing development time and helping the creation of dynamically generated scenes or forms.