1.響應(yīng)式編程思想
不需要考慮調(diào)用順序，只需要考慮結(jié)果，類似于蝴蝶效應(yīng)，產(chǎn)生一個(gè)事件，會(huì)影響很多東西，這些事件像流一樣的傳播出去，借用面向?qū)ο蟮囊痪湓?萬(wàn)物皆是流
int a=3; int b=4; int c=a+b;
int a=0; int b=0; int c=a+b; a=3; b=4;
響應(yīng)式編程思想:不考慮順序，只考慮結(jié)果。變量 a b 值改變就會(huì)影響到 c 。變量 c 與變量 a b 的值綁定，只要變量a 或者b 的值發(fā)生改變 c 的值就發(fā)生改變；時(shí)刻要監(jiān)聽(tīng) a b 值的改變，改變了要馬上響應(yīng) c
2.OC中響應(yīng)式編程思想的使用 KVO時(shí)刻監(jiān)聽(tīng)對(duì)象的屬性變化
Person.h
#import <Foundation/Foundation.h>
@interface Person : NSObject
@property (nonatomic,assign) int age;
@end
ViewController.m
#import "ViewController.h"
#import "Person.h"
@interface ViewController()
@property (nonatomic,strong) Person *p;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
Person *p = [[Person alloc] init];
_p = p;
[p addObserver:self
forKeyPath:@"age"
options:NSKeyValueObservingOptionNew
context:nil];
}
- (void)observeValueForKeyPath:(NSString *)keyPath
ofObject:(id)object
change:(NSDictionary<NSString *,id> *)change
context:(void *)context{
NSLog(@"%d",_p.age);
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
_p.age++;
}
@end
//2016-08-14 19:26:06.176 ZYXKVO[27499:1646080] 1
//2016-08-14 19:26:10.236 ZYXKVO[27499:1646080] 2
//2016-08-14 19:26:10.752 ZYXKVO[27499:1646080] 3
//2016-08-14 19:26:11.136 ZYXKVO[27499:1646080] 4
Person對(duì)象的年齡改變，就會(huì)被觀察者self控制器觀察到，就會(huì)調(diào)用觀察者的 observeValueForKeyPath 方法通知觀察者
只要Person的age發(fā)生改變馬上就有響應(yīng)，這就是 響應(yīng)式編程思想
3.KVO底層實(shí)現(xiàn)機(jī)制
_p.age++;
KVO底層實(shí)現(xiàn):就是判斷有沒(méi)有調(diào)用對(duì)象的set方法
1-對(duì)象p的isa指針是Person.jpg
2-對(duì)象p添加觀察者后isa指針變?yōu)镹SKVONotifying_Person.jpg
# KVO底層實(shí)現(xiàn)過(guò)程:
# 1>給一個(gè)對(duì)象添加觀察者對(duì)象，會(huì)動(dòng)態(tài)創(chuàng)建 "NSKVONotifying_該對(duì)象名" 的一個(gè)對(duì)象，"NSKVONotifying_Person" 是 "Person" 的子類
# 2>修改當(dāng)前對(duì)象p的isa指針指向 "NSKVONotifying_Person"
# 3>只要調(diào)用對(duì)象p的set方法，就會(huì)改為調(diào)用 "NSKVONotifying_Person" 的set方法，因?yàn)閷?duì)象p的isa指針改變了
# 4>重寫(xiě) "NSKVONotifying_Person" 的set方法 : 1.[super set:] 2.通知觀察者對(duì)象的屬性改變
4.模仿KVO實(shí)現(xiàn)，實(shí)現(xiàn)響應(yīng)式編程，運(yùn)行時(shí)機(jī)制
3-對(duì)象p的isa指針是Person.jpg
4-將對(duì)象p的isa指針在運(yùn)行時(shí)改為ZYXKVONotifying_Person.jpg
NSObject+ZYXKVO.h
#import <Foundation/Foundation.h>
@interface NSObject (ZYXKVO)
- (void)zyx_addObserver:(NSObject *)observer
forKeyPath:(NSString *)keyPath
options:(NSKeyValueObservingOptions)options
context:(nullable void *)context;
@end
NSObject+ZYXKVO.m
#import "NSObject+ZYXKVO.h"
#import "ZYXKVONotifying_Person.h"
#import <objc/runtime.h>
@implementation NSObject (ZYXKVO)
- (void)zyx_addObserver:(NSObject *)observer
forKeyPath:(NSString *)keyPath
options:(NSKeyValueObservingOptions)options
context:(void *)context{
// KVO底層實(shí)現(xiàn)過(guò)程:
// 1>給一個(gè)對(duì)象添加觀察者對(duì)象，會(huì)動(dòng)態(tài)創(chuàng)建 "NSKVONotifying_該對(duì)象名" 的一個(gè)對(duì)象，"NSKVONotifying_Person" 是 "Person" 的子類
// 2>修改當(dāng)前對(duì)象p的isa指針指向 "NSKVONotifying_Person"
// 3>只要調(diào)用對(duì)象p的set方法，就會(huì)改為調(diào)用 "NSKVONotifying_Person" 的set方法，因?yàn)閷?duì)象p的isa指針改變了
// 4>重寫(xiě) "NSKVONotifying_Person" 的set方法 : 1.[super set:] 2.通知觀察者對(duì)象的屬性改變
// 分類是不能有屬性的,在運(yùn)行時(shí)動(dòng)態(tài)給分類設(shè)置屬性
// 修改isa指針,本質(zhì)就是改變當(dāng)前對(duì)象的類名
object_setClass(self, ZYXKVONotifying_Person.class);
// 把觀察者對(duì)象保存為當(dāng)前對(duì)象的一個(gè)屬性
// 運(yùn)行時(shí)給 self 對(duì)象添加一個(gè)屬性名為 @"observer" 的屬性 observer
// 引用策略為 nonatomic retain 強(qiáng)引用
// 運(yùn)行時(shí)給self創(chuàng)建一個(gè)強(qiáng)引用屬性關(guān)聯(lián),self強(qiáng)引用觀察者observer對(duì)象
objc_setAssociatedObject(self, @"observer", observer, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
@end
ZYXKVONotifying_Person.h
#import "Person.h"
@interface ZYXKVONotifying_Person : Person
@end
ZYXKVONotifying_Person.m
#import "ZYXKVONotifying_Person.h"
#import <objc/runtime.h>
@implementation ZYXKVONotifying_Person
- (void)setAge:(int)age{
[super setAge:age];
// 對(duì)象p調(diào)用了age的set方法就通知觀察者 p.age 值改變了
id observer = objc_getAssociatedObject(self, @"observer");
// 調(diào)用觀察者的方法
[observer observeValueForKeyPath:@"age" ofObject:self change:nil context:nil];
}
@end
ViewController.m
#import "ViewController.h"
#import "Person.h"
#import "NSObject+ZYXKVO.h"
@interface ViewController()
@property (nonatomic,strong) Person *p;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
Person *p = [[Person alloc] init];
_p = p;
[p zyx_addObserver:self
forKeyPath:@"age"
options:NSKeyValueObservingOptionNew
context:nil];
}
- (void)observeValueForKeyPath:(NSString *)keyPath
ofObject:(id)object
change:(NSDictionary<NSString *,id> *)change
context:(void *)context{
NSLog(@"%d",_p.age);
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
_p.age++;
}
@end
//2016-08-14 20:16:17.529 ZYXKVO[32416:1685663] 1
//2016-08-14 20:16:18.340 ZYXKVO[32416:1685663] 2
//2016-08-14 20:16:18.500 ZYXKVO[32416:1685663] 3
//2016-08-14 20:16:18.788 ZYXKVO[32416:1685663] 5
//2016-08-14 20:16:18.925 ZYXKVO[32416:1685663] 6
這樣就實(shí)現(xiàn)了KVO機(jī)制
[p zyx_addObserver:self forKeyPath:@"age" options:NSKeyValueObservingOptionNew context:nil];
