iOS Runtime学习笔记-优快云博客

本文介绍Objective-C中关联对象的使用方法及方法交换（Swizzling）的实现原理。通过示例展示了如何设置和获取对象关联属性，以及如何通过方法交换改变原有方法的行为。

Associated Objects:

@interface NSObject (AssociatedObject)
@property (nonatomic, strong) id associatedObject;
@end

@implementation NSObject (AssociatedObject)
@dynamic associatedObject;

- (void)setAssociatedObject:(id)object {
     objc_setAssociatedObject(self, @selector(associatedObject), object, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
}

- (id)associatedObject {
    return objc_getAssociatedObject(self, @selector(associatedObject));
}

Swizzling:

+ (void)load{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Class class = [self class];
        SEL originalSEL = @selector(viewWillAppear:);
        SEL swizzledSEL = @selector(xxx_viewWillAppear:);
        
        Method originalMethod = class_getInstanceMethod(class, originalSEL);
        Method swizzledMethod = class_getInstanceMethod(class, swizzledSEL);
        
        BOOL didAddMethod = class_addMethod(class, originalSEL, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod));
        
        if (didAddMethod) {
            class_replaceMethod(class, swizzledSEL, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));
        }else{
            method_exchangeImplementations(originalMethod, swizzledMethod);
        }
        
    });
}

- (void)xxx_viewWillAppear:(BOOL)animated {
    [self xxx_viewWillAppear:animated];
    NSLog(@"viewWillAppear: %@", self);
}

转载于:https://www.cnblogs.com/ficow/p/5383943.html