Person.h
#import<Foundation/Foundation.h> @classAccount; @interfacePerson :NSObject{
@private
int_age;
}
#pragma mark -属性 @property(nonatomic,copy)NSString*name;
@property(nonatomic,retain)Account*account; -(void)showMessage; @end Person.m
#import"Person.h"
#import"Account.h" @implementationPerson -(void)showMessage{
NSLog(@"name=%@,age=%d",_name,_age);
} #pragma mark设置人员账户
-(void)setAccount:(Account*)account{
_account=account;
//添加对Account的监听
[_accountaddObserver:selfforKeyPath:@"balance"options:NSKeyValueObservingOptionNewcontext:nil];
} #pragma mark重写observeValueForKeyPath方法,当账户余额变化后此处获得通知
-(void)observeValueForKeyPath:(NSString*)keyPath ofObject:(id)object change:(NSDictionary*)change context:(void*)context{
if([keyPathisEqualToString:@"balance"]){//这里只处理balance属性
NSLog(@"keyPath=%@,object=%@,newValue=%.2f,context=%@",keyPath,object,[[changeobjectForKey:@"new"]floatValue],context);
}
} #pragma mark重写销毁方法
-(void)dealloc{
[self.accountremoveObserver:selfforKeyPath:@"balance"];//移除监听
} Account.h
#import<Foundation/Foundation.h> @interfaceAccount :NSObject
#pragma mark余额
@property(nonatomic,assign)floatbalance;
@end Account.m
#import"Account.h" @implementationAccount @end Main调用方法
- (void)viewDidLoad {
[superviewDidLoad]; #if0
Person *person1=[[Person alloc]init];
[person1 setValue:@"Kenshin"forKey:@"name"];
[person1 setValue:@28forKey:@"age"];//注意即使一个私有变量仍然可以访问 [person1 showMessage];
//结果:name=Kenshin,age=28
NSLog(@"person1's name is :%@,age is :%@",person1.name,[person1 valueForKey:@"age"]);
//结果:person1's name is :Kenshin,age is :28 Account *account1=[[Account alloc]init];
person1.account=account1;//注意这一步一定要先给account属性赋值,否则下面按路径赋值无法成功,因为account为nil,当然这一步骤也可以写成:[person1 setValue:account1 forKeyPath:@"account"]; [person1 setValue:@.0forKeyPath:@"account.balance"]; NSLog(@"person1's balance is :%.2f",[[person1 valueForKeyPath:@"account.balance"] floatValue]);
//结果:person1's balance is :100000000.00 #else Person*person1=[[Personalloc]init];
person1.name=@"Kenshin"; Account*account1=[[Accountalloc]init];
account1.balance=100000000.0;
person1.account=account1; account1.balance=200000000.0;//注意执行到这一步会触发监听器回调函数observeValueForKeyPath: ofObject: change: context:
#endif }