ios开发--KVO浅析

目标：监听NSMutableArray对象中增加了什么

代码如下：

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

- (void)viewDidLoad
{
    [super viewDidLoad];

    self.dataArray = [NSMutableArray arrayWithObject:@"1"];
    [self addObserver:self forKeyPath:@"dataArray" options:NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context:NULL];

}

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);
}

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

- (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：

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] 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：

1. - (void)viewDidLoad
2. {
3. [super viewDidLoad];
4. self.personObject = [PersonObject personObjectWithBankInstance:[BankObject bankObjectWithAccountBalance:10]];
5. [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
6. }

- (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
}

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);
}

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

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

输出日志：

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.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。