iOS_经验(7)_KVO_手动发送通知

一丶KVO Compliance 原始文档

https://developer.apple.com/library/content/documentation/Cocoa/Conceptual/KeyValueObserving/Articles/KVOCompliance.html

二丶发送通知使用介绍:

2.1自动发送通知;

 ######2.1.1 set方法
  // Call the accessor method.
  [account setName:@"Savings"];
  ######2.1.2 kvc
  // Use setValue:forKey:.
  [account setValue:@"Savings" forKey:@"name"];
  
######2.1.3 kvc 路径法
  // Use a key path, where 'account' is a kvc-compliant property of 'document'.
  [document setValue:@"Savings" forKeyPath:@"account.name"];
  
######2.1.3 kvc 获取一个数组
  // Use mutableArrayValueForKey: to retrieve a relationship proxy object.
  Transaction *newTransaction = <#Create a new transaction for the account#>;
  NSMutableArray *transactions = [account mutableArrayValueForKey:@"transactions"];
  [transactions addObject:newTransaction];

2.2 手动发送通知

2.2.1控制

+ (BOOL)automaticallyNotifiesObserversForKey:(NSString *)key
{
    
    if ([key isEqualToString:@"想要手动控制的key"])return NO;
    
    return [super automaticallyNotifiesObserversForKey:key];
}

2.2.2 手动发送

重写set方法;
- (void)setTmpStr:(NSString *)tmpStr
{
    [self willChangeValueForKey:@"tmpStr"];
    
    _tmpStr = tmpStr;
    
    [self didChangeValueForKey:@"tmpStr"];
}

2.2.3 提升性能的手动发送

- (void)setTmpStr:(NSString *)tmpStr
{
    if (![_tmpStr isEqualToString:tmpStr])
    {
        [self willChangeValueForKey:@"tmpStr"];
        
        _tmpStr = tmpStr;
        
        [self didChangeValueForKey:@"tmpStr"];
    }
}

2.2.4 实现一个key修改,多个key同时修改

- (void)setTmpStr:(NSString *)tmpStr
{
    if (![_tmpStr isEqualToString:tmpStr])
    {
        [self willChangeValueForKey:@"tmpStr"];
        [self willChangeValueForKey:@"修改发送的通知1号Key"];
        [self willChangeValueForKey:@"修改发送的通知2号Key"];
        _tmpStr = tmpStr;
        
        [self didChangeValueForKey:@"tmpStr"];
        [self didChangeValueForKey:@"修改发送的通知1号Key"];
        [self didChangeValueForKey:@"修改发送的通知2号Key"];
    }
}

2.2.5 最后一个,没用过,简单介绍

typedef enum NSKeyValueChange : NSUInteger {
    NSKeyValueChangeSetting = 1,
    NSKeyValueChangeInsertion = 2,
    NSKeyValueChangeRemoval = 3,
    NSKeyValueChangeReplacement = 4
} NSKeyValueChange; 

移除 Transactions 中元素时手动触发 KVO 例子:

- (void)removeTransactionsAtIndexes:(NSIndexSet *)indexes
{
    
    [self willChange:NSKeyValueChangeRemoval valuesAtIndexes:indexes forKey:@"transactions"];
    
    // Remove the transaction objects at the specified indexes.
    
    [self didChange:NSKeyValueChangeRemoval valuesAtIndexes:indexes forKey:@"transactions"];
}