objective-C 2.0

#import <Foundation/Foundation.h>

//:表示公有继承
@interface Person : NSObject
{
    //属性,实例变量,默认权限为protected
    int age;
    //对象声明时必须使用*
    NSString * name;
}  
//生成set和get方法
@property (nonatomic,assign) int age; 

// - 表示实例的方法(消息)，+ 表示类的方法(消息)static
- (void)eat;
- (void)setName:(NSString *)nameValue;

@end

#import "Person.h"

@implementation Person

@synthesize age;

- (void)eat
{
    NSLog(@"eat function called");        
}

- (void)setName:(NSString *)nameValue
{
    if (nameValue)
    {
         //指针不能直接赋值，否则释放时会出现问题
         if (name != nameValue)
         {
                name = nil;
                name = [NSString stringWithString:nameValue];
          }
    }
}

@end

#import "Person.h"
#import <Foundation/Foundation.h>

int main(int argc, const char * argv[])
{
    @autoreleasepool
    {
        //alloc为+方法，init为-方法
        Person * p = [[Person alloc]init];
        
        [p eat];
        //oc字符串必须以@开头
        [p setName:@"yangjing"];
    }
    return 0;
}