结构型之七-享元模式

Flyweight（享元模式）

运用共享技术有效地支持大量细粒度的对象。

比如iOS的RunTime就是享元的一个事件。每个对象调用的方法其实是他对应的类里面实现的。比如NSObject定义了很多方法让所有对象都可以使用。类对象永远只有一个，而对应的实例对象有无数个。

VC.m

//享元工厂，里面包括多个共享的对象。
HCDWebSiteFactory *facoty = [[HCDWebSiteFactory alloc]init];
//虽然生成了两个fx和fy产品展示类型的对象，但是通过共享只初始化了一个产品展示的对象。
HCDWebSite fx = [facoty getWebSiteCategory:@"产品展示"];
HCDUser *user = [[HCDUser alloc]init];
user.name = @"张三";
[fx use:user];
HCDWebSite fy = [facoty getWebSiteCategory:@"产品展示"];
HCDUser *user1 = [[HCDUser alloc]init];
user1.name = @"李四";
[fy use:user1];
//初始化一个博客类型的对象。以后使用都可以共享使用，因为他们有基本相似的功能。
HCDWebSite fz = [facoty getWebSiteCategory:@"博客"];
HCDUser *user2 = [[HCDUser alloc]init];
user2.name = @"王五";
[fz use:user2];

HCDWebSiteFactory.h

@interface HCDWebSiteFactory : NSObject
@property(nonatomic,strong)NSDictionary *flyweights;
-(id<HCDWebSite> )getWebSiteCategory:(NSString *)webkey;
-(NSInteger)getWebSiteCount;
@end

HCDWebSiteFactory.m

@implementation HCDWebSiteFactory
-(instancetype)init{
    self = [super init];
    if (self) {
        _flyweights = [NSDictionary dictionary];
    }
    return self;
}
-(HCDWebSite)getWebSiteCategory:(NSString *)webkey{
    __block HCDWebSite webset = nil;
    [self.flyweights enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {
        if (webkey == key) {
            webset = obj;
            *stop = YES;
        }
    }];
    if (webset == nil) {
        HCDConcreteWebSite  *concreteset = [[HCDConcreteWebSite alloc] init];
        concreteset.webName = webkey;
        webset = concreteset;
        NSMutableDictionary *mutabledic = [NSMutableDictionary dictionaryWithDictionary:self.flyweights];
        [mutabledic setObject:webset forKey:webkey];
        self.flyweights = [NSDictionary dictionaryWithDictionary:mutabledic];
    }
    return webset;
}
-(NSInteger)getWebSiteCount{
    return self.flyweights.count;
}
@end

设计图