目标：监听NSMutableArray对象中增加了什么

代码如下：

- (void)viewDidLoad

{

    [super viewDidLoad];

    self.dataArray = [NSMutableArray arrayWithObject:@"1"];

    [self addObserver:self forKeyPath:@"dataArray" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:NULL];

}

- (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context

{

    NSLog(@"%@", keyPath);

    NSLog(@"%@", object);

    NSLog(@"%@", change);

}

- (IBAction)add:(id)sender

{

    NSArray *addData = [NSArray arrayWithObjects:@"11", @"12", @"13", nil];

    [self.dataArray addObjectsFromArray:addData];

    self.dataArray = [NSMutableArray arrayWithObject:@"2"];

}

输入日志：

2013-01-15 16:05:10.120 KVOTest[2199:907] dataArray

2013-01-15 16:05:10.121 KVOTest[2199:907] <ZZTViewController: 0x20846590>

2013-01-15 16:05:10.123 KVOTest[2199:907] {

    kind = 1;

    new =     (

        2

    );

    old =     (

        1,

        11,

        12,

        13

    );

}

经过测试得如下结论：kvo监听的是对象指针的变动，NSString、int、float等对象的变动(abc = @"123"、abc = 12、abc = 12.2)皆为指针的变动，所以通过此方式来捕捉array的变化是不可行的

但，我们可以通过此方式来做控件属性的变动。如下：

- (void)viewDidLoad

{

    [super viewDidLoad];

    self.personObject = [PersonObject personObjectWithBankInstance:[BankObject bankObjectWithAccountBalance:10]];

    [self.personObject addObserver:self forKeyPath:@"bankInstance.accountBalance" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:NULL];    // 此处注意是监听personObject对象下的bankInstance的accountBalance变化

}

- (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context

{

    NSLog(@"%@", keyPath);

    NSLog(@"%@", object);

    NSLog(@"%@", change);

}

- (IBAction)add:(id)sender

{

    [self.personObject.bankInstance setAccountBalance:2111];

}

输出日志：

2013-01-15 16:05:10.111 KVOTest[2199:907] bankInstance.accountBalance

2013-01-15 16:05:10.116 KVOTest[2199:907] <PersonObject: 0x20856180>

2013-01-15 16:05:10.118 KVOTest[2199:907] {

    kind = 1;

    new = 2111;

    old = 10;

}

如有问题，请留言共同探讨。