KVO键值依赖 KVO键值依赖

一个属性与有限个属性关联，例如下面的totalAge与user1和user2的age息息相关，只要其中一个改变，totalAge就会改变。

// //Person.h // //Created by Walg on 2017/7/29. //Copyright ? 2017年 Walg. All rights reserved. //#import @interface Person : NSObject @property (nonatomic,copy)NSString *pName; @property (nonatomic,assign)NSInteger age; @end

【KVO键值依赖】Person.m中未做任何处理！

// //Card.h // //Created by Walg on 2017/7/29. //Copyright ? 2017年 Walg. All rights reserved. //#import #import "Person.h" @interface Card : NSObject @property (nonatomic,assign)NSInteger totalAge; @property (nonatomic,strong)Person *user1; @property (nonatomic,strong)Person *user2; @end

// //Card.m // //Created by Walg on 2017/7/29. //Copyright ? 2017年 Walg. All rights reserved. //#import "Card.h"@implementation Card- (instancetype)init { self = [super init]; if (self) { _user1 = [[Person alloc] init]; _user2 = [[Person alloc] init]; } return self; }-(NSInteger)totalAge{ return _user1.age+_user2.age; }+(NSSet *)keyPathsForValuesAffectingValueForKey:(NSString *)key{ NSSet *keyPaths = [super keyPathsForValuesAffectingValueForKey:key]; NSArray *moreKeyPaths = nil; if ([key isEqualToString:@"totalAge"]) { moreKeyPaths = [NSArray arrayWithObjects:@"user1.age", @"user2.age", nil]; }if (moreKeyPaths) { keyPaths = [keyPaths setByAddingObjectsFromArray:moreKeyPaths]; } return keyPaths; }@end

使用：

// //ViewController.m //键值依赖 // //Created by Walg on 2017/7/30. //Copyright ? 2017年 Walg. All rights reserved. //#import "ViewController.h" #import "Card.h" @interface ViewController () @property (nonatomic,strong)Card *userCard; @end@implementation ViewControllerstatic NSInteger NewAge(){ static NSInteger newAge = 10; return newAge++; }- (void)viewDidLoad { [super viewDidLoad]; _userCard = [[Card alloc] init]; _userCard.user1.pName = @"a"; _userCard.user1.age = 18; [self.userCard addObserver:self forKeyPath:@"totalAge" options:NSKeyValueObservingOptionNew|NSKeyValueObservingOptionOld context:nil]; }-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context{ NSLog(@"keyPath:%@",keyPath); NSLog(@"object:%@",object); NSLog(@"change:%@",change); }-(void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event{ self.userCard.user2.age = NewAge(); }- (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; }@end

log：

2017-07-30 14:14:07.100 键值依赖[62587:1948971] keyPath:totalAge 2017-07-30 14:14:07.101 键值依赖[62587:1948971] object: 2017-07-30 14:14:07.101 键值依赖[62587:1948971] change:{ kind = 1; new = 28; old = 18; }