Objective-C Fundamentals

Overriding methods
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}
return gender;
}
return -1;
- (void)setName:(NSString *)_name {
name = _name;
}
- (void)setAge:(NSNumber *)_age {
age = _age;
}
- (void)setGender:(Gender)_gender {
gender = _gender;
}
Getter and setter methods are pretty self-explanatory. Getter methods return an
instance variable with the same name. Setter methods take in an object and set it to
an instance variable. The only point of note here is that in the getter methods, make
sure to check if the variables exist. If the name getter was called, for instance, and the
name was never set, an error would be returned without the check. If the name didn’t
exist, a nil value would be returned.
This method is more time consuming than the method we examine next, but it
also allows a nice cutoff point to perform operations when a class’s instance variables
are requested. If, for instance, you want to count the number of times a variable is
called or set, you can do so with these methods.
This is the classic way that getters and setters used to be created, but most developers
now use properties to create them. Properties were introduced by Apple to automatically
generate these very common methods. Refer to section 5.4 for more
information on this automated approach.
6.4 Overriding methods
Overriding methods is another important aspect of subclassing in Objective-C. Just as
a subclass of any class retains the class’s instance variables, it also gains access to all the
class’s instance methods. If you call a method to a class and the compiler sees that a
method with that name doesn’t exist in the class, it goes to the superclass and checks
for the method there (see figure 6.1).
Generally, method overriding is the act of replacing a method from the parent
class with a method that does something different. This is commonly done when creating
class structures, because methods may need to perform slightly differently in a
subclass than they do in the class in which they’re first declared.
Let’s do some method overriding in your new classes. The NSObject class has a
method called
- (NSString)description;
This is a helpful class to override when creating custom classes. It’s likely that during
development you’ll be taking advantage of the NSLog operation to help debug your