Plain Old Objective-C class

Let’s create a simple class Car with model and year properties and getter/setter methods in Objective-C.
In Objective-C the class implementation is split into two parts, the interface definition and the implementation. The interface is defined in a .h file and the implementation in a .m file. The interface has the list of variables and method declarations.
A Car.h file with the definition for Car interface is shown below.

//Car.h
@interface Car : NSObject {
    NSString* model;
    int year;
}
-(int)year;
-(void) setYear:(int)input;

-(NSString*)model;
-(void) setModel:(NSString*)input;

@end

The Car interface has the model and year variables. It also has the definition of getter/setter methods. The ‘get’ prefix word is not required for the getter methods. The minus (-) sign before the method definitions indicate that they are instance methods.

The implementation class Car.m is shown below.

#import "Car.h"

@implementation Car
    -(NSString*) model{
        return model;
    }
    -(void) setModel:(NSString *)input{
        model = input;
    }

    -(int)year{
        return year;
    }
    -(void) setYear:(int)input{
        year = input;
    }
@end

Car.m implements the Car interface and provides the implementation for getter/setters of model and year.
If you want to create an object of Car class and access the methods, you can do it as shown below.

    Car* car1 = [Car alloc];
    [car1 setModel:@"Audi"];
    [car1 setYear:2012];
    NSLog(@"Model: %@, Year of make: %d",[car1 model],[car1 year]);

We have created an object of Car class ‘car1’ and assigned values to the model and year. A method is accessed using [object methodName:params] syntax in Objective-C.
Objective-C 2.0 (released long ago) provides a much easier syntax to define the accessors. We will discuss it in our next post.