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if else for while id break continue self super nil YES NOThree reserved words are special kinds of references to objects: self, super, and nil. You can use these reserved words in any method.
self refers to the object (the WOApplication object, the WOSession object, or the WOComponent object) associated with a script. When you send a message to self, you're telling the object associated with the script to perform a method that's implemented in the script. For example, suppose you have a script that implements the method giveMeARaise. From another method in the same script, you could invoke giveMeARaise as follows:
[self giveMeARaise];This tells the WOApplication, WOSession, or WOComponent object associated with the script to perform its giveMeARaise method.
When you send a message to self, the method doesn't have to be physically located in the script file. Remember that part of the advantage of object-oriented programming is that a subclass automatically implements all of its superclass's methods. For example, WOComponent defines a method named application, which retrieves the WOApplication associated with this component. Thus, you can send this message in any of your components to retrieve the application object:
[self application]WOComponent also defines a session method, so you can do this to retrieve the current session:
[self session]Sometimes, you actually do want to invoke the superclass's method rather than the current object's method. For example, when you initialize an object, you should always give the superclass a chance to perform its initialization method before the current subclass. To do this, you send the init message to super, which represents the superclass of the current object.
- init {
[super init];
// my initialization
return self;
}
The nil word represents an empty object. Any object before it is initialized has the value nil. nil is similar to a null pointer in C. For example, to test whether an object has been allocated and initialized, you do this:
if (myArray == nil) //myArray hasn't been initialized.This next statement also tests to see if myArray is equal to nil:
if (!myArray) //myArray hasn't been initialized.
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