#import <Foundation/Foundation.h>

@interface Person : NSObject

{

   // @public

    int age;

    NSString *name;

}

- (id) init;

- (void) setAge:(int) newAge;

- (void) setName:(NSString *) newName;

@end

@implementation Person

- (id) init

{

    if (self = [super init]) {

        age = 20;

        name = @"jerry";

    }

    return self;

}

- (void) setAge:(int)newAge

{

    if (age == 0)

    {

        age = 20;

    }

    age = newAge;

}

- (void) setName:(NSString *)newName

{

    name = newName;

}

//对name和age方法同时进行封装,不需要在.h文件中提前定义

- (void) setName:(NSString *)newName andAge:(int)newAge

{

    age = newAge;

    name = newName;

}

@end

int main(int argc, const char * argv[]) {

    @autoreleasepool {

//方法一：通过指针来修改age的值，但存在不稳定性，因为只能访问Person类中的public属性，并非随时都有效。而且缺乏安全性

//并且当age的名字改变时，容易因未及时修改而造成无法调用。

        Person *p = [[Person alloc]init];

        p -> age = 10;

//方法二：通过调用set方法来修改age的值，稳定安全。并且可以在set方法中添加限制，提高代码安全性。

        [p setAge:10];

        [p setName:@"nick" andAge:21];

    }

    return 0;

}

#import <Foundation/Foundation.h>

@interface Computer : NSObject

{

    int cpu;

    int inch;

}

@end

@implementation Computer

//进行二次封装

- (void) setCpu:(int)newCpu

{

    cpu = newCpu;

}

- (void) setInch:(int)newInch

{

    inch = newInch;

}

@end

@interface Person : NSObject

{

    Computer *Mac;

}

@end

@implementation Person

- (void) setMac:(Computer *)newMac

{

    [self setnewMac:(Computer *)newMac];

}

//即便之后setMac的名字改变，也可以通过self来接洽而无需修改main.m

- (void) setnewMac:(Computer *)newMac

{

    Mac = newMac;

}

@end

int main(int argc, const char * argv[]) {

    @autoreleasepool {

        Person *p = [[Person alloc]init];

        Computer *Mac = [[Computer alloc]init];

        [Mac setCpu:64];

        [Mac setInch:15];

        [p setMac:Mac];

    }

    return 0;

}