访问集合属性

普通方式访问

valueForKey:
setValue:forKey:

可变代理方式

mutableArrayValueForKey:
mutableArrayValueForKeyPath:
 
mutableSetValueForKey:
mutableSetValueForKeyPath:
 
mutableOrderedSetValueForKey:
mutableOrderedSetValueForKeyPath:

• 当你修改代理对象的时候，添加，删除，替换里面的内容，对应的集合属性的内容也会跟着修改。
• 当试图修改一个非可变集合的内容的时候，效率会特别高
  • 正常的修改非可变集合的方式为
    1. valueForKey:得到non-mutable集合(如 NSArray *array)
    2. 根据这个非可变集合（array），创建一个mutalbe集合(NSMutableArray *mArray)
    3. 修改这个mArray
    4. 通过 setValue:forKey:将修改后的集合重新赋值
  • 可变代理方式
    1. mutableArrayValueForKey:得到mutalbe代理(NSMutableArray *mArray)
    2. 修改这个mArray
    3. 对代理对象的修改自动反馈到对应的属性上面

Account

@interface Account : NSObject

@property (nonatomic, copy) NSString *bankName;
@property (nonatomic, assign) NSInteger money;

@end

Person

@interface Person : NSObject

@property (nonatomic, strong) NSArray *accounts;
@property (nonatomic, copy) NSString *name;
@property (nonatomic, assign) NSInteger age;
@end

ViewController

@interface ViewController ()

@property (nonatomic, strong) Person *person;

@end


- (void)viewDidLoad {
    [super viewDidLoad];
    
    _person = [[Person alloc] init];
    _person.name = @"张三";
    _person.age = 10;
    
    Account *account_1 = [[Account alloc] init];
    account_1.bankName = @"中国银行";
    account_1.money = 100;
    
    Account *account_2 = [[Account alloc] init];
    account_2.bankName = @"交通银行";
    account_2.money = 200;
    _person.accounts = @[account_1, account_2];
    
    
    // Do any additional setup after loading the view.
}

- (IBAction)newAccount:(id)sender {
    
    NSMutableArray *accounts = [self.person mutableArrayValueForKey:@"accounts"];
    
    Account *account_1 = accounts.firstObject;
    account_1.money = 999;
    
    Account *account_3 = [[Account alloc] init];
    account_3.bankName = @"建设银行";
    account_3.money = 500;
    
    [accounts addObject:account_3];
    
    for (Account *account  in self.person.accounts) {

        NSLog(@"name = %@, money = %ld", account.bankName, (long)account.money);
    }
    
}