I really love that binding stuff in JavaFX. I am looking forward until some smart guy implements something similar in Scala…

But I also have some problems with it. Sometimes “on replace” triggers are called with the same values for <old> and <new>. Here is a small sample script that shows it:

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import java.lang.RuntimeException;

/**
 * @author johannes
 */
println( "Starting binding test..." );
var i = 0.5 on replace old {
    println( "i changed to <{i}>" );
    if ( i == old ) {
      throw new RuntimeException( "This will never happen!" );
    }
  };
var b = bind calc( i ) on replace old {
    println( "b has changed from <{old}> to <{b}>" );
    if ( b == old ) {
      println( "!!!!!!!!!!!!!!!!!!!!!!!" );
      println( "Why is on replace called? Both objects are the same: {isSameObject( b, old )}" );
      println( "!!!!!!!!!!!!!!!!!!!!!!!" );
    }
  };

println( "i: {i}" );
i = 0.5;

println( "i: {i}" );
i = 0.9;

println( "i: {i}" );
i = 1.0;

println( "i: {i}" );

function calc( i     ) {
  return i < 1;
}

Of course I have posted a question in the JavaFX forum. But no answers yet….

UPDATE:
Has finally been fixed in 1.3! Now it works as expected.