Objectice-C之类与对象

　　Objectice-C申明一个car接口如下：

#import <Foundation/Foundation.h>

@interface Car : NSObject
{
    int year;
    NSString *make;
    NSString *model;
}
- (void) setMake:(NSString *) aMake andModel:(NSString *) aModel andYear: (int) aYear;
- (void) printCarInfo;
- (int) year;
@end

实现该接口：

#import "Car.h"

@implementation Car
- (id) init
{
    self = [super init];
    if (!self) return nil;
    
    make = nil;
    model = nil;
    year = 1901;
    
    return self;
}

- (void) setMake:(NSString *) aMake andModel:(NSString *) aModel andYear: (int) aYear
{
    make = [NSString stringWithString:aMake];
    model = [NSString stringWithString:aModel];
    year = aYear;
}

- (void) printCarInfo
{
    if (!make) return;
    if (!model) return;
    
    printf("Car Info\n");
    printf("Make: %s\n", [make UTF8String]);
    printf("Model: %s\n", [model UTF8String]);
    printf("Year: %d\n", year);
}

- (int) year
{
    return year;
}
@end

创建对象：

Car *myCar = [[Car alloc] init];

采用先分配内存然后调用的方式，此时sizeof(myCar)的大小为4，sizeof(*myCar)大小为16.

释放对象：

[myCar release];