目標：監聽NSMutableArray對象中增加了什么

代碼如下：

C代碼  

1. - (void)viewDidLoad  
2. {  
3.     [super viewDidLoad];  
4.   
5.     self.dataArray = [NSMutableArray arrayWithObject:@"1"];  
6.     [self addObserver:self forKeyPath:@"dataArray" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:NULL];  
7.        
8. }  

- (void)viewDidLoad{    [super viewDidLoad];    self.dataArray = [NSMutableArray arrayWithObject:@"1"];    [self addObserver:self forKeyPath:@"dataArray" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:NULL];     }

C代碼  

1. - (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context  
2. {  
3.     NSLog(@"%@", keyPath);  
4.     NSLog(@"%@", object);  
5.     NSLog(@"%@", change);  
6. }  

- (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{    NSLog(@"%@", keyPath);    NSLog(@"%@", object);    NSLog(@"%@", change);}

C代碼  

1. - (IBAction)add:(id)sender  
2. {  
3.     NSArray *addData = [NSArray arrayWithObjects:@"11", @"12", @"13", nil];  
4.     [self.dataArray addObjectsFromArray:addData];  
5.       
6.     self.dataArray = [NSMutableArray arrayWithObject:@"2"];  
7. }  

- (IBAction)add:(id)sender{    NSArray *addData = [NSArray arrayWithObjects:@"11", @"12", @"13", nil];    [self.dataArray addObjectsFromArray:addData];        self.dataArray = [NSMutableArray arrayWithObject:@"2"];}

輸入日志：

C代碼  

1. 2013-01-15 16:05:10.120 KVOTest[2199:907] dataArray  
2. 2013-01-15 16:05:10.121 KVOTest[2199:907] <ZZTViewController: 0x20846590>  
3. 2013-01-15 16:05:10.123 KVOTest[2199:907] {  
4.     kind = 1;  
5.     new =     (  
6.         2  
7.     );  
8.     old =     (  
9.         1,  
10.         11,  
11.         12,  
12.         13  
13.     );  
14. }  

2013-01-15 16:05:10.120 KVOTest[2199:907] dataArray2013-01-15 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    );}

經過測試得如下結論：kvo監聽的是對象指針的變動，NSString、int、float等對象的變動(abc = @"123"、abc = 12、abc = 12.2)皆為指針的變動，所以通過此方式來捕捉array的變化是不可行的

但，我們可以通過此方式來做控件屬性的變動。如下：

C代碼  

1. - (void)viewDidLoad  
2. {  
3.     [super viewDidLoad];  
4.       
5.     self.personObject = [PersonObject personObjectWithBankInstance:[BankObject bankObjectWithAccountBalance:10]];  
6.       
7.     [self.personObject addObserver:self forKeyPath:@"bankInstance.accountBalance" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:NULL];    // 此處注意是監聽personObject對象下的bankInstance的accountBalance變化  
8. }  

- (void)viewDidLoad{    [super viewDidLoad];        self.personObject = [PersonObject personObjectWithBankInstance:[BankObject bankObjectWithAccountBalance:10]];        [self.personObject addObserver:self forKeyPath:@"bankInstance.accountBalance" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:NULL];    // 此處注意是監聽personObject對象下的bankInstance的accountBalance變化}

C代碼  

1. - (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context  
2. {  
3.     NSLog(@"%@", keyPath);  
4.     NSLog(@"%@", object);  
5.     NSLog(@"%@", change);  
6. }  

- (void) observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{    NSLog(@"%@", keyPath);    NSLog(@"%@", object);    NSLog(@"%@", change);}

C代碼  

1. - (IBAction)add:(id)sender  
2. {  
3.     [self.personObject.bankInstance setAccountBalance:2111];  
4. }  

- (IBAction)add:(id)sender{    [self.personObject.bankInstance setAccountBalance:2111];}

 輸出日志：

C代碼  

1. 2013-01-15 16:05:10.111 KVOTest[2199:907] bankInstance.accountBalance  
2. 2013-01-15 16:05:10.116 KVOTest[2199:907] <PersonObject: 0x20856180>  
3. 2013-01-15 16:05:10.118 KVOTest[2199:907] {  
4.     kind = 1;  
5.     new = 2111;  
6.     old = 10;  
7. }  

2013-01-15 16:05:10.111 KVOTest[2199:907] bankInstance.accountBalance2013-01-15 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;}

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