扩展NSMutableArray以进行双向关联管理

#import <Foundation/Foundation.h>

@interface NSMutableArray (Association)

- (void)addObject:(id)object withAssociatedObject:(id)associatedObject;
- (void)removeObject:(id)object withAssociatedObject:(id)associatedObject;
- (id)associatedObjectForObject:(id)object;

@end

@implementation NSMutableArray (Association)

- (void)addObject:(id)object withAssociatedObject:(id)associatedObject {
    [self addObject:object];
    objc_setAssociatedObject(object, (__bridge const void *)(self), associatedObject, OBJC_ASSOCIATION_RETAIN);
}

- (void)removeObject:(id)object withAssociatedObject:(id)associatedObject {
    [self removeObject:object];
    objc_setAssociatedObject(object, (__bridge const void *)(self), nil, OBJC_ASSOCIATION_RETAIN);
}

- (id)associatedObjectForObject:(id)object {
    return objc_getAssociatedObject(object, (__bridge const void *)(self));
}

@end

NSMutableArray *array = [NSMutableArray array];

// 添加对象并进行关联
NSString *object1 = @"Object 1";
NSString *associatedObject1 = @"Associated Object 1";
[array addObject:object1 withAssociatedObject:associatedObject1];

// 添加另一个对象并进行关联
NSString *object2 = @"Object 2";
NSString *associatedObject2 = @"Associated Object 2";
[array addObject:object2 withAssociatedObject:associatedObject2];

// 获取与对象1关联的关联对象
NSString *associatedObjectForObj1 = [array associatedObjectForObject:object1];
NSLog(@"%@", associatedObjectForObj1); // 输出：Associated Object 1

// 移除对象1并解除关联
[array removeObject:object1 withAssociatedObject:associatedObject1];

// 再次获取与对象1关联的关联对象
NSString *associatedObjectForObj1AfterRemoval = [array associatedObjectForObject:object1];
NSLog(@"%@", associatedObjectForObj1AfterRemoval); // 输出：(null)