意图：
定义一个用于创建对象的接口，让子类决定实例化哪一个类，从而将一个类的实例化延迟到其子类
适用范围：
对象创建接口统一化，实例化职责子类化、局部化

缺点：
通常客户端只关心需要实现的功能，但是此模式仍然需要客户端指定实例化的类
解决方案：
封装一个工厂方法的适配器，该类负责建立产品之间的关联，从而使得客户端只需要使用其功能即可，而不用在指定具体类
具体实现：
通过适配器定义位移枚举，指定产品的类型以及产品之间的聚合关系，具体产品存储在适配器中以备后续使用，这样的好处是，当更换一种产品品类的时候，无需修改客户端的调用

实践-运营活动优先级管理

某些重要功能成型之后，需要一些列的运营活动来拉新和促活，运营活动需要一个统一的后台来配置（最好如此，不然极难协调），端上则需要开发一套运营系统

定义工厂方法抽象类

@interface ActivityFactory : NSObject

- (void)show;
- (void)dismiss;

@end

定义具体产品类继承与工厂

@interface TopActivity : ActivityFactory

@end

@interface BottomActivity : ActivityFactory

@end

@interface FloatingActivity : ActivityFactory

@end

@interface MiddleActivity : ActivityFactory

@end

每个产品实现抽象方法

- (void)show {
    NSLog(@"%@ show", NSStringFromClass(self.class));
}

- (void)dismiss {
    NSLog(@"%@ dismiss", NSStringFromClass(self.class));
}

定义一个适配器ActivityManager用来管理产品

// 运营位
typedef NS_OPTIONS(NSUInteger, ActivityType) {
    ActivityTypeNone         = 0,      // 无运营位
    ActivityTypeFloating     = 1 << 1, // 浮窗运营位
    ActivityTypeTop          = 1 << 2, // 顶部运营位
    ActivityTypeBottom       = 1 << 3, // 底部运营位
    ActivityTypeMiddle       = 1 << 4, // 中部运营位
};

NS_ASSUME_NONNULL_BEGIN

@interface ActivityManager : NSObject

+ (instancetype)showWithActivity:(ActivityType)type;
- (void)dismissWithActivity:(ActivityType)type;

@end

NS_ASSUME_NONNULL_END

实现如下

@interface ActivityManager ()

@property (nonatomic, strong) NSMutableDictionary *activityDic;

@end

@implementation ActivityManager

+ (instancetype)showWithActivity:(ActivityType)type {
    ActivityManager *manager = ActivityManager.new;
    if (type == ActivityTypeNone) {
        return manager;
    }
    if (type & ActivityTypeFloating) {
        ActivityFactory *factory = [[FloatingActivity alloc] init];
        [factory show];
        [manager.activityDic setObject:factory forKey:NSStringFromClass(FloatingActivity.class)];
    }
    if (type & ActivityTypeTop) {
        ActivityFactory *factory = [[TopActivity alloc] init];
        [factory show];
        [manager.activityDic setObject:factory forKey:NSStringFromClass(TopActivity.class)];
    }
    if (type & ActivityTypeBottom) {
        ActivityFactory *factory = [[BottomActivity alloc] init];
        [factory show];
        [manager.activityDic setObject:factory forKey:NSStringFromClass(BottomActivity.class)];
    }
    if (type & ActivityTypeMiddle) {
        ActivityFactory *factory = [[MiddleActivity alloc] init];
        [factory show];
        [manager.activityDic setObject:factory forKey:NSStringFromClass(MiddleActivity.class)];
    }
    return manager;
}

- (void)dismissWithActivity:(ActivityType)type {
    if (type == ActivityTypeNone) {
        return;
    }
    ActivityFactory *factory = nil;
    if (type & ActivityTypeFloating) {
        factory = [self.activityDic objectForKey:NSStringFromClass(FloatingActivity.class)];
        if (factory) {
            [factory dismiss];
            [self.activityDic removeObjectForKey:NSStringFromClass(FloatingActivity.class)];
        }
    }
    if (type & ActivityTypeTop) {
        factory = [self.activityDic objectForKey:NSStringFromClass(TopActivity.class)];
        if (factory) {
            [factory dismiss];
            [self.activityDic removeObjectForKey:NSStringFromClass(TopActivity.class)];
        }
    }
    if (type & ActivityTypeBottom) {
        factory = [self.activityDic objectForKey:NSStringFromClass(BottomActivity.class)];
        if (factory) {
            [factory dismiss];
            [self.activityDic removeObjectForKey:NSStringFromClass(BottomActivity.class)];
        }
    }
    if (type & ActivityTypeMiddle) {
        factory = [self.activityDic objectForKey:NSStringFromClass(MiddleActivity.class)];
        if (factory) {
            [factory dismiss];
            [self.activityDic removeObjectForKey:NSStringFromClass(MiddleActivity.class)];
        }
    }
}

客户端调用

@interface ViewController ()

@property (nonatomic, strong) ActivityManager *activityManager;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    self.activityManager = [ActivityManager showWithActivity:ActivityTypeTop | ActivityTypeMiddle];
    [self.activityManager dismissWithActivity:ActivityTypeTop];
}

总结

工厂方法模式配合适配器使用，会具备更好的拓展性，工厂方法的核心是，产品能抽象出统一的接口，然而现实场景中一定会有特殊功能的产品，这时候适配器就更有用了，负责兼容产品的特殊属性，本文demo地址