Friday, July 31, 2009

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Binding Sequences

Today we
one of the most powerful features of JavaFX which is the binding between data, this gives us the possibility of linking two variables each either by the change in value one, or by evaluating an expression. We also have the ability to assign triggers that are blocks of code which are executed by changing the value of a variable. Contents


  • Binding Overview
  • Binding and Binding Objects and Functions
  • Binding Sequences with
  • Replace Triggers


Binding Overview
start saying that to make the binding between variables we using the bind keyword, there is also an expression bound now see which creates a broader relationship.

Binding and Objects
Consider an example where we create a binding between two variables. 
  var x = 0; 
 bind def y = x; 
 x = 1; 
 println (y), / / \u200b\u200band now worth 1 
 x = 50; 
 println (y), / / \u200b\u200band now worth 50
Here we see as we only modify the values \u200b\u200bof the variable x this automatically reflected in the variable y.
Now we will see a similar binding but when we make binding between objects. Var 
  myStreet = "1 Main Street"; 
 Mycity var = "Santa Clara"; 
 MYSTAT var = "CA"; 
 myZip var = "95050"; 
 
 
 class Address {var street; 
 var city; 
 var state; 
 var zip; 
 
 
} bind def address = {
 Street Address: myStreet; 
 city: Mycity; 
 state: MYSTAT; 
 zip: myZip; 
}; 
 
 println ("== address.street address.street {} "); 
 myStreet =" 100 Maple Street "
 println (" address.street address.street == {} ");
Here we define the Address class and then define, 4 variables to start this object, creating our object we do with the word bind, this means that our variable address will always have its attributes updated based on the values \u200b\u200bof the variables with which it was initiated.
If you run the example we see that the result is
address.street == 1 == address.street
Main Street 100 Maple Street
An important point to consider is that this type of binding for each modification, generate a new Address object and assigns it again the variable.
Another way to do this without generating a new binding object is as follows var 
  
 myStreet = "1 Main Street"; 
 Mycity var = "Santa Clara"; 
 MYSTAT var = "CA" var myZip 
 = "95050"; 
 
 
 class Address {var street; 
 var city; 
 var state; 
 var zip;} 
 
 
 def address = {
 Street Address: bind myStreet; 
 city: Mycity bind; 
 state: bind MYSTAT; 
 zip: bind myZip; 
}; 
 
 println ("address.street address.street == {}"); 
 myStreet = "100 Maple Street" 
 println ("address . street address.street == {} ");
The only difference is that here does not bind to the object but on each attribute.

Binding and Functions
This is where keyword bound at stake, we must not confuse this with the bind are two different things in combination give us some specific functionality. An example of
bind and bound to understand how it works and how to use 
  / / Step 1 
 var scale = 1.0; 
 
 / / Paso 2 
 class Point {
 var x: Number; 
 var y: Number; 
} 
 
 / / Paso 3 
 bound function make point (xPos: Number, yPos: Number): Point {
 Point {
 x: xPos * scale 
 y: yPos * scale 
} 
} 
 
 / / Paso 4 
 var MyX = \u200b\u200b3.0; 
 var sell = 3.0; 
 def pt = bind sweet point (MyX, sell) ; 
 println (pt.x); 
 
 / / Paso 5 
 MyX = \u200b\u200b10.0; 
 println (pt.x); 
 
 / / Paso 6 
 scale = 2.0; 
 println (pt.x);
Entendamos barrier por ejemplo Paso Paso.
Step 1 :
Here we define a variable of type Number and initialise at 1.0

Step 2: Define the Point class


Step 3: Create a function
which we mark the attribute bound here we know that there are two types of functions are bound and not-bound to behave differently if so with a variable binding.
not-bound functions are executed only if their parameter change, otherwise the bound functions are always executed

Step 4: Create
the initialize variables and do a bind between the function and a variable of type Point. Step 5

:
myX Change the value of this variable as was used as a parameter of the bind function is triggered and the function changes the values \u200b\u200bof Point

Step 6:
Change the value of the scale and as this is a bound function also perform the function again and we change the values \u200b\u200bof Point
If you run the example the result is:

20.0 10.0 3.0

If we removed the bound of the function the result is:

10.0 10.0 3.0


Binding Sequences with
Here we use a bind between sequences but also using the expression for. Quietly could make a common bind between two sequences as if they were variables, but to see the power of this we use an expression for as follows 
  / / define the sequence 1 
 SEQ1 var = [1 .. 10]; 
 
 / / define the sequence 2, but with the difference that each item is multiplied by two 
 seq2 = bind def for (item in SEQ1) item * 2; 
 printSeqs (); 
 printSeqs 
 function () {
 println ("First Sequence:"); 
 for (i in SEQ1) {println (i);} 
 println ("Second Sequence:"); 
 for (i in seq2) {println (i);}}

If you run the example the result is as follows:
First Sequence:

1 2 3


4 5 6


7 8 9


10 Second Sequence:

2 4 6


8
10 12 16


14 18 20


is clearly seen as the sequence 2 is related to the sequence 1, but also applies a multiplication on each item, to confirm the bind we will insert an item in the sequence 1 and this should be present in the sequence 2 
  / / We define the sequence 1 
 SEQ1 var = [1 .. 10]; 
 
 / / define the sequence 2, but with the difference that each item is multiplied by two seq2 = bind def 
 for (Item in SEQ1) item * 2; 
 Into SEQ1 insert 11; 
 printSeqs (); 
 printSeqs 
 function () {
 println ("First Sequence:"); 
 for (i in SEQ1) {println (i) 
} println ("Second Sequence:"); 
 for (i in seq2) {println (i);}}
If we run the example we see that the sequence 1 is now item 1 and tier 2 is item 22. Replace Triggers


Replace Triggers are called blocks of code that we assign the variables to be executed when their values \u200b\u200bchange. Here we use the statement on set to replace the code block we want to run 
  var password = "foo" on replace oldValue {
 println ("\\ nALERT! Password has changed!"); 
 println ("Old Value: {oldValue}"); 
 println ("New Value: {password} ");} 
; 
 password =" bar ";
First create the password where initialize variables with the value" foo "(Presumably" Now I will explain why I put this-) and we continued to replace the ruling on a name chosen by the previous value and then define the code to execute. to run the following example we will see

ALERT! Password has changed!
Old Value:
New Value: foo

ALERT! Password has changed!
Old Value: New Value
foo: bar

see that runs twice as the variable is initialized to a start Null why our initialization "foo" is assumed.

Well with this we will terminate the introduction to the features of JavaFX as scripting would be part of, now we turn to the visual part where we start to use all this knowledge. Greetings


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