写在前面：今天周末，没有出门，就结合这两天学的，敲了这个demo, 水平有限，表要喷，当然很多都是站在大牛的肩膀上，没有大牛的肩膀，我早就饿死了.....对于比较懒惰的我来说，今天过的很充实啊，听着民谣、玩着代码、隔壁还坐着一个看电视的媳妇儿，哈哈。
在iOS开发中，苹果给我们提供了很多回机制，KVO(key-value-observing)就是其一。在某个对象注册监听者后，在被监听的对象发生改变时，对象会发送一个通知给监听者，以便监听者执行回调操作。今天这篇文章主要是为了实现结合函数式编程思想，自定义KVO的。其主要步骤是动态生成子类和实现消息转发，具体如代码：
步骤
- KVO 实例
- 动态生成子类
- setter方法
- 消息转发
先来创建两个类，分别是People类和KVOInfoModel类
People类
People.h
# import <Foundation/Foundation.h> @interface People : NSObject @property (nonatomic,strong) NSString *name; @property (nonatomic,strong) NSString *age; @end
KVOInfoModel.h
#import <Foundation/Foundation.h> typedef void(^KVOBlock) (id observer,NSString *keyPath,id newValue,id oldValue); @interface KVOInfoModel : NSObject @property (nonatomic, copy) NSString *keyPath; @property (nonatomic, weak) NSObject *observer; @property (nonatomic, copy) KVOBlock blockHandle; - (instancetype)initWithObserver:(NSObject *)observer keyPath:(NSString *)keyPath observerHandle:(KVOBlock)blockHandle; @end
KVOInfoModel.m
#import "KVOInfoModel.h" @implementation KVOInfoModel - (instancetype)initWithObserver:(NSObject *)observer keyPath:(NSString *)keyPath observerHandle:(KVOBlock)blockHandle{ if (self = [super init]) { _keyPath = keyPath; _observer = observer; _blockHandle = blockHandle; } return self; } @end
再来一个NSObject (KVO) .h
#import <Foundation/Foundation.h> #import "KVOInfoModel.h" @interface NSObject (KVO) - (void)addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath withBlock:(KVOBlock)block; @end
NSObject (KVO) .m
#import "NSObject+KVO.h"
#import <objc/message.h>
#import "KVOInfoModel.h"
@implementation NSObject (KVO)
- (void)addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath withBlock:(KVOBlock)block{
//1. 实例 SEL 方法选择器
SEL setterSeletor = NSSelectorFromString(setterfromGetter(keyPath));
Method setterMethod = class_getInstanceMethod(object_getClass(self), setterSeletor);
if (!setterMethod) {
@throw [NSException exceptionWithName:NSInvalidArgumentException reason:@"没有setter方法" userInfo:nil];
}
//2. 动态创建子类
NSString *superClassName = NSStringFromClass([self class]);
Class newClas = [self creatClassFromSuperClass:superClassName];
//ias swilzing 替换父类
object_setClass(self, newClas);
const char *types = method_getTypeEncoding(setterMethod);
//3:setter方法
class_addMethod(newClas, setterSeletor, (IMP)KVO_Setter, types);
//4;消息转发
KVOInfoModel *info = [[KVOInfoModel alloc] initWithObserver:observer keyPath:keyPath observerHandle:block];
NSMutableArray *obserArray = objc_getAssociatedObject(self, (__bridge const void * _Nonnull)(KVOAssioKey));
if (!obserArray) {
obserArray = [NSMutableArray arrayWithCapacity:1];
/**
关联属性
1:对象
2:关键字
3:关联对象
4:策略
*/
objc_setAssociatedObject(self, (__bridge const void * _Nonnull)(KVOAssioKey), obserArray, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}
[obserArray addObject:info]; }
pragma mark - 函数区域
/* 将name转变成setName: */
static NSString * setterfromGetter(NSString * getter){
if (getter.length <= 0) {return nil;}
// name
NSString *firstString = [[getter substringToIndex:1] uppercaseString]; // N
NSString *leaveSTring = [getter substringFromIndex:1]; // ame
return [NSString stringWithFormat:@"set%@%@:",firstString,leaveSTring];
}
/* 将setName转变成name */
static NSString *getterfromSetter(NSString * setter){
if (setter.length <= 0 || ![setter hasPrefix:@"set"] || ![setter hasSuffix:@":"]) { return nil;}
//setName: ===>> Name: ====> Name ==> name
NSRange range = NSMakeRange(3, setter.length-4);
NSString *getter = [setter substringWithRange:range];
NSString *firstString = [[getter substringToIndex:1] lowercaseString]; //n
getter = [getter stringByReplacingCharactersInRange:NSMakeRange(0, 1) withString:firstString];
return getter;
}
/* 动态生成子类*/
static Class KVC_Class(id self){
return class_getSuperclass(object_getClass(self));
}
- (Class)creatClassFromSuperClass:(NSString *)superName{
Class superClass = NSClassFromString(superName);
/**
动态生成类
1:父类
2:名字
3:空间
*/
// NSKVONotifiying_ ===>>> KCKVC_
NSString *newClassName = [KVOPre stringByAppendingString:superName];
Class newClass = NSClassFromString(newClassName);
if (newClass) {
return newClass;
}
newClass = objc_allocateClassPair(superClass, newClassName.UTF8String, 0);
//添加Class
Method classMethod = class_getClassMethod(superClass, @selector(class));
const char *type = method_getTypeEncoding(classMethod);
/**
添加方法
1:类
2:方法名字
3:IMP 函数实现的指针
4:类型
*/
class_addMethod(newClass, @selector(class), (IMP)KVC_Class, type);
//注册类
objc_registerClassPair(newClass);
return newClass;
}
static void KVO_Setter(id self,SEL _cmd,id newValue){
//手动监听
//_cmd ===
NSString *setterName = NSStringFromSelector(_cmd);
NSString *getterName = getterfromSetter(setterName);
id oldValue = [self valueForKey:getterName];
[self willChangeValueForKey:getterName];
//消息转发
void(*KCMsgSend)(void *,SEL,id) = (void *)objc_msgSendSuper;
struct objc_super kcSuperStruct = {
.receiver = self,
.super_class = class_getSuperclass(object_getClass(self))
};
KCMsgSend(&kcSuperStruct,_cmd,newValue);
[self didChangeValueForKey:getterName];
NSMutableArray *obserArray = objc_getAssociatedObject(self, (__bridge const void * _Nonnull)(KVOAssioKey));
for (KVOInfoModel *info in obserArray) {
dispatch_async(dispatch_queue_create(0, 0), ^{
info.blockHandle(self, info.keyPath, newValue, oldValue);
});
}
}
@end
VC回调KVO
#import "ViewController.h"
#import "People.h"
#import "NSObject+KVO.h"
@interface ViewController ()
@property (nonatomic,strong) People *people;
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.people = [[People alloc] init];
[self.people addObserver:self forKeyPath:@"name" withBlock:^(id observer, NSString *keyPath, id newValue, id oldValue) {
NSLog(@"%@==%@",newValue,oldValue);
}];
[self.people addObserver:self forKeyPath:@"age" withBlock:^(id observer, NSString *keyPath, id newValue, id oldValue) {
NSLog(@"%@==%@",newValue,oldValue);
}];
self.people.name = @"hanhan";
self.people.age = @"100";
}
- (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
self.people.name = [NSString stringWithFormat:@"%@+",self.people.name];
self.people.age = [NSString stringWithFormat:@"%@+",self.people.age];
}
- (void)dealloc{
[self.people removeObserver:self forKeyPath:@"name"];
}
这样就是实现了一个自定义KVO，面试时用起来绝对6的一比，还没有具体使用到项目中，今后会继续学习，不断提升自己。
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