kvo的observationInfo

观察者信息的注册：

<NSKeyValueObservationInfo 0x600000708d60> (

<NSKeyValueObservance 0x6000009143f0: Observer: 0x7f9a0b508ef0, Key path: tpStr, Options: <New: YES, Old: YES, Prior: NO> Context: 0x0, Property: 0x600000914480>

<NSKeyValueObservance 0x600000914420: Observer: 0x7f9a0b508ef0, Key path: eggo, Options: <New: YES, Old: YES, Prior: NO> Context: 0x0, Property: 0x6000009146f0>

)

/* Take or return a pointer that identifies information about all of the observers that are registered with the receiver, the options that were used at registration-time, etc. The default implementation of these methods store observation info in a global dictionary keyed by the receivers' pointers. For improved performance, you can override these methods to store the opaque data pointer in an instance variable. Overrides of these methods must not attempt to send Objective-C messages to the passed-in observation info, including -retain and -release.

*/

@property (nullable) void *observationInfo NS_RETURNS_INNER_POINTER;

函数调用栈：

Foundation`-[NSObject(NSKeyValueObservingCustomization) observationInfo]

Foundation`_NSKeyValueRetainedObservationInfoForObject + 53

Foundation`-[NSObject(NSKeyValueObserverRegistration) _addObserver:forProperty:options:context:] + 337

Foundation`-[NSObject(NSKeyValueObserverRegistration) addObserver:forKeyPath:options:context:] + 103

@interface ViewController ()

@property(nonatomic, strong) NSString *pt;

@end

编译系统自动生成设置访问控制；编译系统自动生成kvc控制符；

kvo在这个基础上执行；

所有的kvc操作控制在编译前都已经完成；

属性的kvc操作在编译后运行前完成；

setvalue：for相关的操作属于运行时系统；在kvo的机制能能截获。

self.pt = @"ddddd";

[ViewController setPt:]

https://github.com/farcaller/cocotron/blob/af740de86c9bee84c59ffc74d27e5df9e22e1391/Foundation/NSKeyValueCoding/NSKeyValueObserving.m

   // set info options
   info->observer=observer;
   info->options=options;
   info->context=context;
   info->object=self;
   [info setKeyPath:keyPath];

-(void)setObservationInfo:(void*)info
{
	if(!observationInfos)
		observationInfos=[NSMutableDictionary new];
	[observationInfos setObject:[NSValue valueWithPointer:info] forKey:[NSValue valueWithPointer:self]];
}

+(void*)observationInfo
{
	return [[observationInfos objectForKey:[NSValue valueWithPointer:self]] pointerValue];
}

+(void)setObservationInfo:(void*)info
{
	if(!observationInfos)
		observationInfos=[NSMutableDictionary new];
	[observationInfos setObject:[NSValue valueWithPointer:info] forKey:[NSValue valueWithPointer:self]];