Objective-C Fundamentals

Overriding methods
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}
"for $%@ per year with expertise in %@",
[super description], classes, salary, areaOfExpertise];
} else {
return [NSString stringWithFormat:
@"%@. I am a female currently teaching %@ "
"for $%@ per year with expertise in %@",
[super description], classes, salary, areaOfExpertise];
}
Once again, you’ve overridden the description method so that when you use it in your
NSLog method, it will be called rather than the NSObject version of it (see the following
listing).
Listing 6.8
Overriding the description method in Student
- (NSString *)description {
if(gender == Male) {
return [NSString stringWithFormat:
@"%@. I am a male currently enrolled in %@ "
"for %@ credits with %@ as my major",
[super description], classes, numberOfCredits, major];
} else {
return [NSString stringWithFormat:
@"%@. I am a female currently enrolled in %@ "
"for %@ credits with %@ as my major",
[super description], classes, numberOfCredits, major];
}
}
In Teacher and Student, you use their superclass’s (Person) description method to
fill in the first part of the string and then use the individual instance variables of
Student and Teacher, respectively. Custom methods you create can be overridden,
and so can almost all of the include libraries’ methods. Another commonly overridden
method is
- (void)dealloc
This is the method used for memory management when objects need to be released.
This method and its implementation are covered in more detail in chapter 9.
All that’s left to do with these classes is test them and the methods you’ve made for
them. If you go into your Application Delegate and enter the following code into the
applicationDidFinishLaunching:withOptions: method, you’ll be able to see all of
your classes and subclasses working together.
Listing 6.9
Test code for your subclasses
- (void)applicationDidFinishLaunching:(UIApplication *)application
withOptions:(NSDictionary*)options {
// Override point for customization after app launch
[self.window makeKeyAndVisible];