Default bind access on class fields?

Question

Hi,
I have a question on binding. Look at the following code:
1 var readyLight = Circle {
2     centerX: 12
3     centerY: 12
4     radius: 12
5     stroke: Color.GRAY
6     fill: bind RadialGradient {
7          centerX: 8
8          centerY: 8
9          radius: 12
10          proportional: false
11          stops: [
12               Stop {
13                    offset: 0
14                    color: Color.WHITE
15               }
16               Stop {
17                    offset: 1
18                    color: if (readyButton.selected) Color.GOLD else Color.GRAY
19               }
20          ]
21     }
22}This circle uses a radial gradient to fill itself. The 18th line uses a condition statement to dynamically determine the color of the second stop of the gradient. However, I think this line should use a "bind" keyword to keep the color dynamic. But when I added a bind the 18th line, an error showed up:"color has script only (default) bind access in javafx.scene.paint.Stop". I am confused about this, I haven't seen any document saying the "default bind access" thing.
This demo is from the official online UI tutorial: http://java.sun.com/javafx/1/tutorials/ui/layout/index.html
Any help on this is appreciated!

Answer 1

This works because you are creating a new RadialGradient instance whenever selected changes. You are not just changing the color.
It would be more efficient to define a selectedGradient and an unselectedGradient and use them:
def selectedGradient  : RadialGradient = RadialGradient {
          centerX: 8
          centerY: 8
          radius: 12
          proportional: false
          stops: [
               Stop {
                    offset: 0
                    color: Color.WHITE
               Stop {
                    offset: 1
                    color: Color.GOLD
def unselectedGradient  : RadialGradient = RadialGradient {
          centerX: 8
          centerY: 8
          radius: 12
          proportional: false
          stops: [
               Stop {
                    offset: 0
                    color: Color.WHITE
               Stop {
                    offset: 1
                    color: Color.GRAY
def readyLight = Circle {
     centerX: 50
     centerY: 50
     radius: 12
     stroke: Color.GRAY
     fill: bind if (selected) selectedGradient else unselectedGradient
}