设计模式-享元模式

Contents

1. 1. 享元模式、我理解就类似缓存优化，先取缓存，没有就创建新的，再存入缓存.
2. 2. 抽象享元接口定义
3. 3. 具体享元实现
4. 4. 所有具体享元对象的工厂
5. 5. demo示例
6. 6. 复合享元、让一些简单的享元对象组合在一起
7. 7. #添加复合享元的实现，复杂享元不需要存储到缓存，所以不需要identifier.
8. 8. 修改享元工厂，添加创建复合享元的接口方法
9. 9. demo示例

享元模式、我理解就类似缓存优化，先取缓存，没有就创建新的，再存入缓存.

• 简单 享元
• 复合 享元

---

抽象享元接口定义

/**
*  抽象享元接口
*/
@protocol Flyweight <NSObject>

/**
*  功能函数定义
*/
- (void)operation:(NSString *)state;

@end

具体享元实现

#import <Foundation/Foundation.h>

//实现抽象享元接口
#import "Flyweight.h"

/**
*  一个具体享元
*/
@interface ConcreteFlyweight : NSObject <Flyweight>

/**
*  使用一个唯一表示实例化
*/
- (instancetype)initWithIdentifier:(NSString *)identifier;

@end

#import "ConcreteFlyweight.h"

@interface ConcreteFlyweight ()

@property (nonatomic, copy) NSString *identifier;

@end

@implementation ConcreteFlyweight

- (instancetype)initWithIdentifier:(NSString *)identifier {
self = [super init];
if (self) {
_identifier = identifier;
}
return self;
}

- (void)operation:(NSString *)state {
NSLog(@"外部state = %@\n", state);
NSLog(@"内部state = %@\n", _identifier);
}

@end

所有具体享元对象的工厂

//
//  FlyWeightFactory.h
//  demos

#import <Foundation/Foundation.h>

//享元抽象接口
#import "Flyweight.h"

/**
*  所有具体享元的工厂
*/
@interface FlyWeightFactory : NSObject

/**
*  单例工厂
*/
+ (instancetype)sharedInstacne;

/**
*  传入唯一标识查询享元
*/
- (id<Flyweight>)concreteFlyWeightWithIdentifier:(NSString *)identifer;

@end

//
//  FlyWeightFactory.m
//  demos
//
#import "FlyWeightFactory.h"

#import "ConcreteFlyweight.h"

@interface FlyWeightFactory ()

@property (nonatomic, strong) NSMutableDictionary *mapping;

@end

@implementation FlyWeightFactory

+ (instancetype)sharedInstacne {
static FlyWeightFactory *factory = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
factory = [[FlyWeightFactory alloc] init];
});
return factory;
}

- (NSMutableDictionary *)mapping {
if (!_mapping) {
_mapping = [[NSMutableDictionary alloc] init];
}
return _mapping;
}

- (id<Flyweight>)concreteFlyWeightWithIdentifier:(NSString *)identifer
{
id<Flyweight> flyweight = nil;

//1. 首先从缓存查询
flyweight = [self.mapping objectForKey:identifer];

//2. 如果缓存不存在，就创建一个新的，并存入缓存
if (!flyweight) {

//2.1
flyweight = [[ConcreteFlyweight alloc] initWithIdentifier:identifer];

//2.2
[self.mapping setObject:flyweight forKey:identifer];
}

return flyweight;
}

@end

demo示例

#import "FlyweightTest.h"

//只导入 享元工厂
#import "FlyWeightFactory.h"

@implementation FlyweightTest

- (void)test {

//1. 从享元工厂查询一个标识对应的享元对象
id<Flyweight> flyweight = [[FlyWeightFactory sharedInstacne] concreteFlyWeightWithIdentifier:@"identifier"];

//2. 调用接口定义的方法
[flyweight operation:@"hahahah"];
}

@end

---

复合享元、让一些简单的享元对象组合在一起

#添加复合享元的实现，复杂享元不需要存储到缓存，所以不需要identifier.

//
//  ConcreteCompositeFlyweight.h
//  demos
//
#import <Foundation/Foundation.h>

//实现抽象享元接口
#import "Flyweight.h"

@interface ConcreteCompositeFlyweight : NSObject <Flyweight>

/**
*  继续可以添加 子享元对象
*/
- (void)addFlayweight:(id<Flyweight>)flyweight
WithIdentifier:(NSString *)identifier;


@end

//
//  ConcreteCompositeFlyweight.m
//  demos
//
#import "ConcreteCompositeFlyweight.h"

@interface ConcreteCompositeFlyweight ()

@property (nonatomic, strong) NSMutableDictionary *mapping;

@end

@implementation ConcreteCompositeFlyweight

- (NSMutableDictionary *)mapping {
if (!_mapping) {
_mapping = [[NSMutableDictionary alloc] init];
}
return _mapping;
}

- (void)addFlayweight:(id<Flyweight>)flyweight
WithIdentifier:(NSString *)identifier
{
//保存到字典中
[self.mapping setObject:flyweight forKey:identifier];
}

- (void)operation:(NSString *)state {

//遍历保存的所有享元对象
[self.mapping enumerateKeysAndObjectsUsingBlock:^(NSString *  _Nonnull key,
id<Flyweight>  _Nonnull obj,
BOOL * _Nonnull stop)
{
//调用每一个子享元对象
[obj operation:state];
}];
}

@end

修改享元工厂，添加创建复合享元的接口方法

//
//  FlyWeightFactory.h
//  demos
//
#import <Foundation/Foundation.h>

//享元抽象接口
#import "Flyweight.h"

/**
*  所有具体享元的工厂
*/
@interface FlyWeightFactory : NSObject

/**
*  单例工厂
*/
+ (instancetype)sharedInstacne;

/**
*  获取简单享元
*/
- (id<Flyweight>)concreteFlyWeightWithIdentifier:(NSString *)identifer;

/**
*  获取复杂享元
*/
- (id<Flyweight>)compositeFlyWeightWithIdentifier:(NSArray<NSString *> *)identifers;

@end

//
//  FlyWeightFactory.m
//  demos
//

#import "FlyWeightFactory.h"

//简单享元实现
#import "ConcreteFlyweight.h"

//复杂享元实现
#import "ConcreteCompositeFlyweight.h"

@interface FlyWeightFactory ()

@property (nonatomic, strong) NSMutableDictionary *mapping;

@end

@implementation FlyWeightFactory

+ (instancetype)sharedInstacne {
static FlyWeightFactory *factory = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
factory = [[FlyWeightFactory alloc] init];
});
return factory;
}

- (NSMutableDictionary *)mapping {
if (!_mapping) {
_mapping = [[NSMutableDictionary alloc] init];
}
return _mapping;
}

- (id<Flyweight>)concreteFlyWeightWithIdentifier:(NSString *)identifer
{
id<Flyweight> flyweight = nil;

//1. 首先从缓存查询
flyweight = [self.mapping objectForKey:identifer];

//2. 如果缓存不存在，就创建一个新的，并存入缓存
if (!flyweight) {

//2.1
flyweight = [[ConcreteFlyweight alloc] initWithIdentifier:identifer];

//2.2
[self.mapping setObject:flyweight forKey:identifer];
}

return flyweight;
}

- (id<Flyweight>)compositeFlyWeightWithIdentifier:(NSArray<NSString *> *)identifers
{
//1. 创建一个复杂享元对象
ConcreteCompositeFlyweight *compositeFlyweight = [ConcreteCompositeFlyweight new];

//2. 一次创建（查询）子享元对象
id<Flyweight> flyweight = nil;
for (NSString *identifier in identifers) {

//2.1 <最重要>: 查询循环获取简单享元对象
flyweight = [self concreteFlyWeightWithIdentifier:identifier];

//2.2 注册到 复合享元中
[compositeFlyweight addFlayweight:flyweight
WithIdentifier:identifier];
}

//3.
return compositeFlyweight;
}

@end

demo示例

#import "FlyweightTest.h"

//只导入 享元工厂
#import "FlyWeightFactory.h"

@implementation FlyweightTest

- (void)test {

//1. 定义组合的简单享元的标识
NSArray<NSString *> *identifiers = @[@"identifier1", @"identifier2", @"identifier3"];

//2. 从享元工厂获取复杂享元
id<Flyweight> flyweight = [[FlyWeightFactory sharedInstacne] compositeFlyWeightWithIdentifier:identifiers];

//3. 调用复合享元
[flyweight operation:@"hahahah"];
}

@end