JavaFX Primer - JavaFX: Developing Rich Internet Applications - page 40

extends clause. To specify a specific function or variable, use the mixin class
name with the function or variable name. This is shown in the following code.
public class My Positioner extends Positioner,
AnotherPositioner {
var offset = 10.0;
public override bound function
centerX(node: Node, within: Node) : Number {
Positioner.centerX(node, within) + offset;
}
}
Mixins may also define variables, with or without default values and triggers.
The subclass either inherits these variables or must override the variable declara-
tion. The following listing demonstrates this.
public mixin class Positioner {
public var offset: Number = 10.0;
}
public class My Positioner extends Positioner {
public override var offset = 5.0 on replace {
println("{offset}");
}
}
If a class extends a JavaFX class and one or more mixin s, the JavaFX class takes
precedence over the mixin classes for variable initialization. If the variable is
declared in a superclass, the default value specified in the superclass is used; if
no default value is specified in the superclass, the “default value” for the type of
that variable is used. For the mixin classes, precedence is based on the order they
are defined in the extends clause. If a variable declared in a mixin has a default
value, and the variable is overridden without a default value in the main class, the
initial value specified in the mixin is used.
Mixins may also have init and postinit blocks. Mixin init and postinit blocks
are run after the super class's init and postinit blocks and before the subclass's
init and postinit blocks. Init and postinit blocks from the mixin classes
are run in the order they are declared in the extends clause for the subclass.
Object Literals
In JavaFX, objects are instantiated using object literals . This is a declarative syntax
using the name of the class that you want to create, followed by a list of initializ-