Synchronize Data Models—Binding and Triggers - JavaFX: Developing Rich Internet Applications - page 89

Our final example demonstrates the full power of triggers as it deals with an
assignment of a sequence slice:
var s1 : Integer[] = [ 2,4,6,8,10 ] on replace
s1Orig[begin..end]=n
{
s2[begin..end] = s1[begin..end];
}
var s2 : Integer[];
print("s1: "); println(s1);
print("s2: "); println(s2);
s1[0..2] = [3,6,9];
print("s1: "); println(s1);
print("s2: "); println(s2);
delete s1[0..2];
print("s1: "); println(s1);
print("s2: "); println(s2);
The trigger contains five arbitrarily named variables, and in the context of this
example, they have the following meanings:
s1 is the sequence after all the changes have been applied.
s1Orig represents the previous value of the s1 sequence. As such, it is the
same type as s1 .
begin is the first index of the sequence slice that has been updated.
end is the last index of the sequence slice that has been updated. Both begin
and end are Integer types.
n represents the sequence of values that will be replacing the slice of
s1Orig[begin..end] .
The output of this code looks like this:
s1: [ 2, 4, 6, 8, 10 ]
s2: [ ]
s1: [ 3, 6, 9, 8, 10 ]
s2: [ 3, 6, 9 ]
s1: [ 8, 10 ]
s2: [ 8, 10 ]
For our final example, we'll contrast how bind and on replace behave when
instance variables are inherited and overridden from a superclass. The code
block that follows contains two classes, the first of which, called MyClass , con-
tains a public name variable that is both bound and has a trigger. The second