Apple WebObjects 3.5 Manual do Utilizador descarregar pdf (Página 46)

Chapter 3 Common Methods

Initialization and Deallocation Methods

Like all objects, WOApplication, WOSession, and WOComponent implement

initialization methods (or constructors in Java). Because most subclasses require

some unique initialization code, these are the methods that you override most

frequently. In WebScript, the initialization methods are

init and awake. In Java, the

initialization methods are the constructor for the class and

awake.

Both

init and awake perform initialization tasks, but they are invoked at different

times during an object’s life. The

init message (or the constructor in Java) is sent

once, when the object is ﬁrst created. In contrast,

awake is sent at the beginning

of each cycle of the request-response loop that the object is involved in. Thus,

it may be sent several times during an object’s life.

Complementing

awake and init are the sleep and dealloc methods. These methods

let objects deallocate their instance variables and perform other clean-up tasks.

The

sleep method is invoked at the end of each cycle of the request-response

loop, whereas the

dealloc method is invoked at the end of the object’s life.

The

dealloc method is used primarily for Objective-C objects. Standard dealloc

methods in Objective-C send each instance variable a

release message to make

sure that the instance variables are freed. WebScript and Java, because they

have automatic garbage collection, usually make a deallocation method

unnecessary. If you ﬁnd it necessary, you can implement

dealloc in WebScript and

ﬁnalize in Java.

The Structures of init and awake

The init method must begin with an invocation of super’s init method and must

end by returning

self.

- init {

[super init];

/* initializations go here */

return self;

}

Likewise, in Java, the constructor must begin with an invocation of the

superclass’s constructor (as with all Java classes):

public Application() {

super();

/* initializations go here */

}

The awake method has no such structure. In it, you don’t need to send a message

super or return anything.

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