two AS3 newbie questions

[Incrue]

So, now one more question...
what is binding?
Here
http://labs.macromedia.com/wiki/inde...:Learning_Tips
they say:
"Binding should always be done to strongly-typed data items, not to properties of type Object.
The lack of type safety with type Object can result in accidental coding mistakes, so the compiler will flag this as a warning. Binding to a property of something of type Object, such as selectedItem.name, will cause a warning; you need to use strongly-typed data items and cast, as in EmployeeInfo(selectedItem).name."

[hangalot]

a binding is a way to make your view or model update automatically. the flex framework allows you to write certain metaTags and the compiler then generates the code for you to take care of what happens in terms of the stuff getting updated.

[Incrue]

I dont know if i should create a new thread cos those are not just two questions anymore
1 public and private are now public and internal, rigth?

2 What is override?

3 What is Dereferencing?

[hangalot]

there is public , protected, private and internal.
public is easy to understand.
protected works like this: if i have an instance of the class a protected method acts like a private method aka i can't call it from the outside. however if i subclass that class, i can change the bahevaiour of the function by overriding it, but then i have to use the override keyword to signify that i am overriding existing behaviour. and i can call that protected from subclasses
private works the same in terms of its visibility from the outside, but i cannot override the methods in subclasses nor call it.
internal's scope means its availivble to all classes in the same package and suclasses.


i think you should get what the override keyword does from what i have said already.
dereferencing means deleting a variable that holds a reference to an object. its not like an oficial term, but search garbage collector and refrence counting.

[webninja]

Keep in mind that binding is done at compile time. That means something like this won't work:

var x:uint;

x = {boundProperty} * 3;

No error or warning will be generated, but you'll get the value of {boundProperty} without it being multiplyed by 3.

[Incrue]

Originally Posted by hangalot

there is public , protected, private and internal.
public is easy to understand.
protected works like this: if i have an instance of the class a protected method acts like a private method aka i can't call it from the outside. however if i subclass that class, i can change the bahevaiour of the function by overriding it, but then i have to use the override keyword to signify that i am overriding existing behaviour. and i can call that protected from subclasses
private works the same in terms of its visibility from the outside, but i cannot override the methods in subclasses nor call it.
internal's scope means its availivble to all classes in the same package and suclasses.

Inst best OOP practice to use get and set?Like function getSomething and set like setSomething?And when making a class defining wich methods and properties others should have acess?So i dont understand this stuff to acess things who weren't designed to be acessible
So, its sounds like a useless things to learn, cos if i will have acess to internal stuff only with get and set i can just make only those methods public and all the rest of the other things private, or internal,or protected

[webninja]

In any OO design, it is very good practice to isolate access to the internals of a class so that only members of that class or classes derrived from it have access.

Getters and setters are basic practce and in AS3 there is even a dedicated syntax for it which aids binding.

One of the goals of OO design is to promote code resuability. This is accomplished by coding classes that do a specific bit of work. You start out with a classes that accomplish very generic tasks and then subclass the class a few times adding specificity. you'll find that you can then reuse the base classes. If you go accessing the varibals from all over your code you won't be able to reuse it. Have a look at the AS3 class lib docs and you'll see just how often they use the same classes near the root of the tree.

When you have a bug, you'll have a lot of trouble figuring out what can change what. As your conventional non-OO project grows, fixing bugs will become more complex. When every varible is global and you have functions that access stuff from all over your source, it does not take long before you lose track of what's happening. Any little change can impact the whole project, which leads to more bugs.

[Incrue]

Ok
What i didnt understand is:When making the class you design what everyone everywhere will have acess, and these will work with get and set, right till here...
So when comes to internal, all other classes in the package can acess the thing, but arent they acessing things who are not suposed to be acessible?
So that this is not best oop practice?
Now override, i supose override is:i take some method, change what he does but keep his name
I may be wrong, but i understand that i should use -protected- only if i intend to make some subclass override some method of my class
But again, isnt this against the good oop practice?Cos someone is acessing thing who were not designed to be acessible?
And when i am going to need to do this?

[Tink]

No this is better OOP than what you can do with public and private alone.

Lets say you have a method that ONLY other classes in the same package can access. You can now limit the access to what is required using internal. This is much better than making it public to everything.

This works the same with protected. If you subclass a class and you need to access it methods in your subclasses you can mark the method protected. This limits the access to subclasses only. Without it, you again would have to make it public. Therefore you can now be stricter, which is better.

i should use -protected- only if i intend to make some subclass override some method of my class

That is incorrect. You use protected for any method or variable that you want to access from a subclass.

override is used when you want to alter a method that is inherited from you superclass. It must return tha same type and take exactly the same parameters as the original method.

You may also be interested in 'final'. specifying a method as final means that it cannot be overriden. so if you had a superclass with a method you want to be able to access from a subclass, but you don't want your subclass to be able to override it, you specify the original method as final.

// This cannot be overriden, but can be accessed by subclasses.
protected final function methodName():void
{
// Actions here.
}

[Incrue]

Ok, thanks everyone for the help