Ios development-KVO analysis, ios-kvo Analysis

Ios development-KVO analysis, ios-kvo Analysis
 

Target: Listen to what is added to the NSMutableArray object

 

The Code is as follows:

C code

-(Void) viewDidLoad

{

[Super viewDidLoad];

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

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

}

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

 

C code

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

{

NSLog (@ "% @", keyPath );

NSLog (@ "% @", object );

NSLog (@ "% @", change );

}

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

 

C code

-(IBAction) add :( id) sender

{

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

[Self. dataArray addObjectsFromArray: addData];

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

}

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

 

Input log:

C code

16:05:10. 120 KVOTest [2199: 907] dataArray

16:05:10. 121 KVOTest [2199: 907] <ZZTViewController: 0x20846590>

16:05:10. 123 KVOTest [2199: 907] {

Kind = 1;

New = (

2

);

Old = (

1,

11,

12,

13

);

}

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    );}

 

 

The test result shows that kvo listens for changes in object pointers, NSString, int, float, and other objects (abc = @ "123", abc = 12, abc = 12.2) all are pointer changes, so it is not feasible to capture array changes.

 

However, we can use this method to change the control attributes. As follows:

C code

-(Void) viewDidLoad

{

[Super viewDidLoad];

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

[Self. personObject addObserver: self forKeyPath: @ "bankInstance. accountBalance" options: NSKeyValueObservingOptionNew | condition context: NULL]; // you can view the change in the accountBalance of bankInstance under the personObject.

}

-(Void) viewDidLoad {[super viewDidLoad]; self. personObject = [PersonObject personObjectWithBankInstance: [BankObject bankObjectWithAccountBalance: 10]; [self. personObject addObserver: self forKeyPath: @ "bankInstance. accountBalance "options: NSKeyValueObservingOptionNew | NSKeyValueObservingOptionOld context: NULL]; // you can check the change in the accountBalance of bankInstance under the personObject object}

 

C code

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

{

NSLog (@ "% @", keyPath );

NSLog (@ "% @", object );

NSLog (@ "% @", change );

}

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

 

C code

-(IBAction) add :( id) sender

{

[Self. personObject. bankInstance setAccountBalance: 2111];

}

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

Output log:

C code

16:05:10. 111 KVOTest [2199: 907] bankInstance. accountBalance

16:05:10. 116 KVOTest [2199: 907] <PersonObject: 0x20856180>

16:05:10. 118 KVOTest [2199: 907] {

Kind = 1;

New = 2111;

Old = 10;

}

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;}

 

If you have any questions, please leave a message for further discussion.