Runtime

isa详解

isa

isa位域

Union共用体实践

1. 通过 & 和 | 运算 简化传值

typedef NS_OPTIONS(NSInteger,RereshTypeEnum) {
    // 1 向左移动的位数
    refreshOneType = 1 << 0,//0b0001
    refreshTwoType = 1 << 1,//0b0010
    refreshThreeType = 1 << 2,//0b100
    refreshFourType = 1 << 3,//0b1000
};

-(void)setRefreshType:(RereshTypeEnum)type{
    if (type&refreshOneType) {
        NSLog(@"包含one");
    }
    
    if (type&refreshTwoType) {
        NSLog(@"包含two");
    }
    
    if (type&refreshThreeType) {
        NSLog(@"包含three");
    }
    
    if (type&refreshFourType) {
        NSLog(@"包含four");
    }
}

// 调用
 Person * p = [[Person alloc] init];
 [p setRefreshType:refreshOneType | refreshTwoType];

Class 方法缓存

image.png

objc_msgSend执行流程

1. 消息发送

   
   
   消息发送

2. 动态方法解析

/**
    实例方法的动态解析
 */
- (void)testMethod{
    NSLog(@"实例方法---动态方法解析来到了");
}
+ (BOOL)resolveInstanceMethod:(SEL)sel{
    
    if (sel == @selector(resolvenMethodTest)) {
        
        //获取到要动态解析的调用方法
        Method method = (Method)class_getInstanceMethod(self, @selector(testMethod));
        
        //添加调用的方法，实现到解析的方法上去。
         class_addMethod(self, sel, method_getImplementation(method), method_getTypeEncoding(method));
        
        //返回YES，代表有动态添加方法
        return YES;
    }
    return [super resolveInstanceMethod:sel];
    
}
/**
    类方法的动态解析
 */
+ (void)classTestMethod{
    NSLog(@"类方法---动态方法解析来到了");
}

+(BOOL)resolveClassMethod:(SEL)sel{
    
    if (sel == @selector(classResolvenMethodTest)) {
        
        //获取 动态解析的类方法
        Method method = (Method)class_getClassMethod(self, @selector(classTestMethod));
        
        // object_getClass 获取类对象
        class_addMethod(object_getClass(self), sel, method_getImplementation(method), method_getTypeEncoding(method));
        
        return YES;
    }
    return [super resolveClassMethod:sel];
}

动态方法解析

3. 消息转发

/**
    消息转发
 */

- (id)forwardingTargetForSelector:(SEL)aSelector{
    if (aSelector == @selector(forwardingMethodTest)) {
        //返回可以进行转发的对象
        Son * s= [[Son alloc] init];
        return s;
    }
    return [super forwardingTargetForSelector:aSelector];
}

--------------------------------------------
- (id)forwardingTargetForSelector:(SEL)aSelector{
    if (aSelector == @selector(forwardingMethodTest)) {
        //如果返回nil，则执行
        return nil;
    }
    return [super forwardingTargetForSelector:aSelector];
}

- (id)forwardingTargetForSelector:(SEL)aSelector{
    if (aSelector == @selector(forwardingMethodTest)) {
        return nil;
    }
    return [super forwardingTargetForSelector:aSelector];
}

//NSMethodSignature 方法签名 包括方法的返回值 和
-(NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector{
    
    if (aSelector == @selector(forwardingMethodTest)) {

        return [[[Son alloc] init] methodSignatureForSelector:aSelector];
    }
    return [super methodSignatureForSelector:aSelector];
}

// NSInvocation 封装了方法的调用  调用者 方法名 参数
-(void)forwardInvocation:(NSInvocation *)anInvocation{
    
    NSLog(@"%@",anInvocation);
    NSLog(@"%@ %@",anInvocation.target,NSStringFromSelector(anInvocation.selector));
    
    [anInvocation invokeWithTarget:[[Son alloc] init]];
    
}