iOS KVC補充及執行個體

iOS KVC補充及執行個體
KVC 補充及執行個體怎麼擷取值 和 修改值—–>How

 - (void)setValue:(id)value forKey:(NSString *)key - (id)valueForKey:(NSString *)key - (id)valueForKey:(NSString *)key //以 key 作為標示符,擷取其對應的屬性值 - (void)setValue:(id)value forKey:(NSString *)key //以 key 作為標示符設定其對應的屬性值 - (id)valueForUndefinedKey:(NSString *)key - (void)setNilValueForKey:(NSString *)key ``` Demo    建立一個QYPerson 類繼承於 NSObject    QYPerson.h ``` #import @interface QYPerson : NSObject@property (nonatomic, strong) NSString *name;@property (nonatomic, assign) int age;- (void)changeName;@end

在 QYPerson.m 檔案中實現上面的方法

#import QYPerson.h@implementation QYPerson- (void)changeName{    _name = @changeName;}@end

建立一個 QYPersonMonitor 的類用來監視 QYPerson 中的 name 屬性
在. m 檔案中實現對 QYPerson 中 name 屬性的監視

 #import QYPersonMonitor.h@implementation QYPersonMonitor// 2. 回調的方法 當觀察的值改變的時候，該方法會被調用- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{    if ([keyPath isEqual:@name]) {        NSLog(@change name: old :%@,   new : %@,[change objectForKey:NSKeyValueChangeOldKey],[change objectForKey:NSKeyValueChangeNewKey]);    }}@end

在控制器中初始化監視的對象以及被監視的對象,註冊觀察者

 #import ViewController.h#import QYPerson.h#import QYPersonMonitor.h@interface ViewController ()@property (nonatomic, strong) QYPerson *person;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    //初始化被監視的對象    _person = [[QYPerson alloc] init];    _person.name = @zhangsan;    _person.age = 18;    //監視對象    QYPersonMonitor *personMonitor = [[QYPersonMonitor alloc] init];    // 1. 註冊了一個觀察者    [_person addObserver:personMonitor forKeyPath:@name options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:nil];    //初始化的值    NSLog(@person's name is %@,_person.name);    //通過 setvalue 的方法,此時 QYPersonMonitor 的監視將被調用    [_person setValue:@(lisi by KVC) forKey:@name];    //列印通過 kvc 方式修改後的值    NSLog(@person's name get by kvc is %@,[_person valueForKey:@name]);    //通過.文法修改的效果和通過 setvalue 是一致的    _person.name = @name change by .name= wangwu;    //通過 person 自己的函數來更改 name 屬性    [_person changeName];}@end

列印結果如下:
**2015-07-29 16:38:59.802 SetDemo[3764:1391043] person’s name is zhangsan
2015-07-29 16:38:59.802 SetDemo[3764:1391043] change name: old :zhangsan, new : (lisi by KVC)
2015-07-29 16:38:59.802 SetDemo[3764:1391043] person’s name get by kvc is (lisi by KVC)
2015-07-29 16:38:59.802 SetDemo[3764:1391043] change name: old :(lisi by KVC), new : name change by .name= wangwu**