iOS开发

自定义KVO(二)

2.2.2 优化Hook逻辑

上面在+ load中Hook dealloc方法是在NSObject分类中处理的，那么意味着所有的类的dealloc方法都被Hook了。显然这么做是不合理的。
逻辑就是仅对需要的类进行Hook dealloc方法，所以将Hook延迟到addObserver中：

- (void)hp_addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath block:(HPKVOBlock)block {

  ……
//hook dealloc

 [[observer class] hp_methodSwizzleWithClass:[observer class] oriSEL:NSSelectorFromString(@"dealloc") swizzledSEL:@selector(hp_dealloc) isClassMethod:NO];

}

但是只应该对dealloc hook一次，否则又交换回来了。要么做标记，要么在创建kvo子类的时候进行hook。显然在创建子类的时候更合适。修改逻辑如下：

//申请类-注册类-添加方法
- (Class)_creatKVOClassWithKeyPath:(NSString *)keyPath observer:(NSObject *)observer {
//这里重写class后kvo子类也返回的是父类的名字

    NSString *superClassName = NSStringFromClass([self class]);

    NSString *newClassName = [NSString stringWithFormat:@"%@%@",kHPBlockKVOClassPrefix,superClassName];

    Class newClass = NSClassFromString(newClassName);
//类是否存在
if (!newClass)  {//不存在需要创建类
//1：申请类 父类、新类名称、额外空间

        newClass = objc_allocateClassPair([self class], newClassName.UTF8String, 0);
//2：注册类
objc_registerClassPair(newClass);
//3：添加class方法，class返回父类信息 这里是`-class`

        SEL classSEL = NSSelectorFromString(@"class");

        Method classMethod = class_getInstanceMethod([self class], classSEL);
const char *classTypes = method_getTypeEncoding(classMethod);
class_addMethod(newClass, classSEL, (IMP)_hp_class, classTypes);

//hook dealloc

        [[observer class] hp_methodSwizzleWithClass:[observer class] oriSEL:NSSelectorFromString(@"dealloc") swizzledSEL:@selector(hp_dealloc) isClassMethod:NO];

    }
//4：添加setter方法

    SEL setterSEL = NSSelectorFromString(_setterForGetter(keyPath));

    Method setterMethod = class_getInstanceMethod([self class], setterSEL);
const char *setterTypes = method_getTypeEncoding(setterMethod);
class_addMethod(newClass, setterSEL, (IMP)_hp_setter, setterTypes);

return newClass;

}

完整实现代码：

typedef void(^HPKVOBlock)(id observer,NSString *keyPath,id oldValue,id newValue);

@interface NSObject (HP_KVO_Block)

- (void)hp_addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath block:(HPKVOBlock)block;

- (void)hp_removeObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath;

@end

#import "NSObject+HP_KVO_Block.h"
#import <objc/runtime.h>
#import <objc/message.h>
#import "HPKVOInfo.h"

static NSString *const kHPBlockKVOClassPrefix = @"HPKVONotifying_";
static NSString *const kHPBlockKVOAssiociateKey = @"HPKVOAssiociateKey";

static NSString *const kHPBlockKVOObserverdAssiociateKey = @"HPKVOObserverdAssiociateKey";

@interface HPKVOBlockInfo : NSObject

@property (nonatomic, weak) id observer;
@property (nonatomic, copy) NSString  *keyPath;
@property (nonatomic, copy) HPKVOBlock  handleBlock;

@end

@implementation HPKVOBlockInfo

- (instancetype)initWitObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath handleBlock:(HPKVOBlock)block {
if (self=[super init]) {

        _observer = observer;

        _keyPath  = keyPath;

        _handleBlock = block;

    }
return self;

}

@end

@interface HPKVOObservedInfo : NSObject

@property (nonatomic, weak) id observerd;
@property (nonatomic, copy) NSString  *keyPath;

@end

@implementation HPKVOObservedInfo

- (instancetype)initWitObserverd:(NSObject *)observerd forKeyPath:(NSString *)keyPath {
if (self=[super init]) {

        _observerd = observerd;

        _keyPath  = keyPath;

    }
return self;

}

@end

@implementation NSObject (HP_KVO_Block)


- (void)hp_addObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath block:(HPKVOBlock)block {
//1.参数判断 以及 setter检查
if (!observer || !keyPath) return;

    BOOL result = [self _handleSetterMethodFromKeyPath:keyPath];
if (!result) return;

//2.isa_swizzle 申请类-注册类-添加方法

    Class newClass = [self _creatKVOClassWithKeyPath:keyPath observer:observer];

//3.isa 指向子类
object_setClass(self, newClass);
//4.setter逻辑处理
//保存观察者信息-数组

    HPKVOBlockInfo *kvoInfo = [[HPKVOBlockInfo alloc] initWitObserver:observer forKeyPath:keyPath handleBlock:block];

    NSMutableArray *observerArray = objc_getAssociatedObject(self, (__bridge const void * _Nonnull)(kHPBlockKVOAssiociateKey));
if (!observerArray) {

        observerArray = [NSMutableArray arrayWithCapacity:1];

    }

    [observerArray addObject:kvoInfo];
objc_setAssociatedObject(self, (__bridge const void * _Nonnull)(kHPBlockKVOAssiociateKey), observerArray, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

//保存被观察者信息

    HPKVOObservedInfo *kvoObservedInfo = [[HPKVOObservedInfo alloc] initWitObserverd:self forKeyPath:keyPath];

    NSMutableArray *observerdArray = objc_getAssociatedObject(observer, (__bridge const void * _Nonnull)(kHPBlockKVOObserverdAssiociateKey));
if (!observerdArray) {

        observerdArray = [NSMutableArray arrayWithCapacity:1];

    }

    [observerdArray addObject:kvoObservedInfo];
objc_setAssociatedObject(observer, (__bridge const void * _Nonnull)(kHPBlockKVOObserverdAssiociateKey), observerdArray, OBJC_ASSOCIATION_RETAIN_NONATOMIC);

}

- (void)hp_removeObserver:(NSObject *)observer forKeyPath:(NSString *)keyPath {

    NSMutableArray *observerArray = objc_getAssociatedObject(self, (__bridge const void * _Nonnull)(kHPBlockKVOAssiociateKey));
if (observerArray.count <= 0) {
return;

    }


    NSMutableArray *tempArray = [observerArray mutableCopy];
for (HPKVOInfo *info in tempArray) {
if ([info.keyPath isEqualToString:keyPath]) {
if (info.observer) {
if (info.observer == observer) {

                    [observerArray removeObject:info];

                }

            } else {

                [observerArray removeObject:info];

            }

        }

    }
objc_setAssociatedObject(self, (__bridge const void * _Nonnull)(kHPBlockKVOAssiociateKey), observerArray, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
//已经全部移除了
if (observerArray.count <= 0) {
//isa指回给父类

        Class superClass = [self class];
object_setClass(self, superClass);

    }

}

- (BOOL)_handleSetterMethodFromKeyPath:(NSString *)keyPath {

    SEL setterSeletor = NSSelectorFromString(_setterForGetter(keyPath));

    Method setterMethod = class_getInstanceMethod(object_getClass(self), setterSeletor);
NSAssert(setterMethod, @"%@ setter is not exist",keyPath);
return setterMethod ? YES : NO;

}

// 从get方法获取set方法的名称 key -> setKey
static NSString *_setterForGetter(NSString *getter) {
if (getter.length <= 0) { return nil;}

    NSString *firstString = [[getter substringToIndex:1] uppercaseString];

    NSString *otherString = [getter substringFromIndex:1];
return [NSString stringWithFormat:@"set%@%@:",firstString,otherString];

}

//申请类-注册类-添加方法
- (Class)_creatKVOClassWithKeyPath:(NSString *)keyPath observer:(NSObject *)observer {
//这里重写class后kvo子类也返回的是父类的名字

    NSString *superClassName = NSStringFromClass([self class]);

    NSString *newClassName = [NSString stringWithFormat:@"%@%@",kHPBlockKVOClassPrefix,superClassName];

    Class newClass = NSClassFromString(newClassName);
//类是否存在
if (!newClass)  {//不存在需要创建类
//1：申请类 父类、新类名称、额外空间

        newClass = objc_allocateClassPair([self class], newClassName.UTF8String, 0);
//2：注册类
objc_registerClassPair(newClass);
//3：添加class方法，class返回父类信息 这里是`-class`

        SEL classSEL = NSSelectorFromString(@"class");

        Method classMethod = class_getInstanceMethod([self class], classSEL);
const char *classTypes = method_getTypeEncoding(classMethod);
class_addMethod(newClass, classSEL, (IMP)_hp_class, classTypes);

//hook dealloc

        [[observer class] hp_methodSwizzleWithClass:[observer class] oriSEL:NSSelectorFromString(@"dealloc") swizzledSEL:@selector(hp_dealloc) isClassMethod:NO];

    }
//4：添加setter方法

    SEL setterSEL = NSSelectorFromString(_setterForGetter(keyPath));

    Method setterMethod = class_getInstanceMethod([self class], setterSEL);
const char *setterTypes = method_getTypeEncoding(setterMethod);
class_addMethod(newClass, setterSEL, (IMP)_hp_setter, setterTypes);

return newClass;

}

//返回父类信息

Class _hp_class(id self,SEL _cmd) {
return class_getSuperclass(object_getClass(self));

}

static void _hp_setter(id self,SEL _cmd,id newValue) {
//自动开关判断，省略
//保存旧值

    NSString *keyPath = _getterForSetter(NSStringFromSelector(_cmd));

    id oldValue = [self valueForKey:keyPath];
//1.调用父类的setter(也可以通过performSelector调用)
void (*hp_msgSendSuper)(void *,SEL , id) = (void *)objc_msgSendSuper;
struct objc_super super_struct = {

        .receiver = self,

        .super_class = class_getSuperclass(object_getClass(self)),

    };
hp_msgSendSuper(&super_struct,_cmd,newValue);

//2.通知观察者

    NSMutableArray *observerArray = objc_getAssociatedObject(self, (__bridge const void * _Nonnull)(kHPBlockKVOAssiociateKey));
for (HPKVOBlockInfo *info in observerArray) {//循环调用,可能添加多次。
if ([info.keyPath isEqualToString:keyPath] && info.handleBlock && info.observer) {
dispatch_async(dispatch_get_global_queue(0, 0), ^{

                info.handleBlock(info.observer, keyPath, oldValue, newValue);

            });

        }

    }

}

//获取getter
static NSString *_getterForSetter(NSString *setter){
if (setter.length <= 0 || ![setter hasPrefix:@"set"] || ![setter hasSuffix:@":"]) { return nil;}

    NSRange range = NSMakeRange(3, setter.length - 4);

    NSString *getter = [setter substringWithRange:range];

    NSString *firstString = [[getter substringToIndex:1] lowercaseString];
return  [getter stringByReplacingCharactersInRange:NSMakeRange(0, 1) withString:firstString];

}

+ (void)hp_methodSwizzleWithClass:(Class)cls oriSEL:(SEL)oriSEL swizzledSEL:(SEL)swizzledSEL isClassMethod:(BOOL)isClassMethod {
if (!cls) {
NSLog(@"class is nil");
return;

    }
if (!swizzledSEL) {
NSLog(@"swizzledSEL is nil");
return;

    }
//类/元类

    Class swizzleClass = isClassMethod ? object_getClass(cls) : cls;

    Method oriMethod = class_getInstanceMethod(swizzleClass, oriSEL);

    Method swiMethod = class_getInstanceMethod(swizzleClass, swizzledSEL);
if (!oriMethod) {//原始方法没有实现
// 在oriMethod为nil时，替换后将swizzledSEL复制一个空实现
class_addMethod(swizzleClass, oriSEL, method_getImplementation(swiMethod), method_getTypeEncoding(swiMethod));
//添加一个空的实现
method_setImplementation(swiMethod, imp_implementationWithBlock(^(id self, SEL _cmd){
NSLog(@"imp default null implementation");

        }));

    }
//自己没有则会添加成功，自己有添加失败

    BOOL success = class_addMethod(swizzleClass, oriSEL, method_getImplementation(swiMethod), method_getTypeEncoding(oriMethod));
if (success) {//自己没有方法添加一个，添加成功则证明自己没有。
class_replaceMethod(swizzleClass, swizzledSEL, method_getImplementation(oriMethod), method_getTypeEncoding(oriMethod));

    } else { //自己有直接进行交换
method_exchangeImplementations(oriMethod, swiMethod);

    }

}

- (void)hp_dealloc {

    NSMutableArray *observerdArray = objc_getAssociatedObject(self, (__bridge const void * _Nonnull)(kHPBlockKVOObserverdAssiociateKey));
for (HPKVOObservedInfo *info in observerdArray) {
if (info.observerd) {

            [info.observerd hp_removeObserver:self forKeyPath:info.keyPath];

        }

    }

    [self hp_dealloc];

}

@end

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2021-08-20

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自定义KVO(二)

2.2.2 优化Hook逻辑

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