iOS 開發中總會用到各種緩存，YYCache或許是你最好的選擇。性能上有優勢，用法也很簡單。作者ibireme
1.簡單架構圖
@interface YYCache : NSObject
// 讀取目前資料庫名稱
@property (copy, readonly) NSString *name;
// memoryCache記憶體緩存，diskCache檔案緩存
@property (strong, readonly) YYMemoryCache *memoryCache;
@property (strong, readonly) YYDiskCache *diskCache;
// 可通過下面三種方法來執行個體化YYCache對象
- (nullable instancetype)initWithName:(NSString *)name;
- (nullable instancetype)initWithPath:(NSString *)path NS_DESIGNATED_INITIALIZER;
+ (nullable instancetype)cacheWithPath:(NSString *)path;
// 禁止通過下面兩個方式執行個體化對象
- (instancetype)init UNAVAILABLE_ATTRIBUTE;
+ (instancetype)new __attribute__((unavailable("new方法不可用，請用initWithName:")));
// 通過key判斷是否緩存了某個東西，第二個法是異步執行,異步回調
- (BOOL)containsObjectForKey:(NSString *)key;
- (void)containsObjectForKey:(NSString *)key withBlock:(nullable void(^)(NSString *key, BOOL contains))block;
// 讀--通過key讀取緩存，第二個法是異步執行,異步回調
- (nullable id<NSCoding>)objectForKey:(NSString *)key;
- (void)objectForKey:(NSString *)key withBlock:(nullable void(^)(NSString *key, id<NSCoding> object))block;
// 增、改--緩存對象(可緩存遵從NSCoding協定的對象)，第二個法是異步執行,異步回調
- (void)setObject:(nullable id<NSCoding>)object forKey:(NSString *)key;
- (void)setObject:(nullable id<NSCoding>)object forKey:(NSString *)key withBlock:(nullable void(^)(void))block;
// 删--删除緩存
- (void)removeObjectForKey:(NSString *)key;
- (void)removeObjectForKey:(NSString *)key withBlock:(nullable void(^)(NSString *key))block;
- (void)removeAllObjects;
- (void)removeAllObjectsWithBlock:(void(^)(void))block;
- (void)removeAllObjectsWithProgressBlock:(nullable void(^)(int removedCount, int totalCount))progress
endBlock:(nullable void(^)(BOOL error))end;
@end
3.YYCache使用
// 0.初始化YYCache
YYCache *cache = [YYCache cacheWithName:@"mydb"];
// 1.緩存普通字元
[cache setObject:@"漢斯哈哈哈" forKey:@"name"];
NSString *name = (NSString *)[cache objectForKey:@"name"];
NSLog(@"name: %@", name);
// 2.緩存模型
[cache setObject:(id<NSCoding>)model forKey:@"user"];
// 3.緩存數組
NSMutableArray *array = @[].mutableCopy;
for (NSInteger i = 0; i < 10; i ++) {
[array addObject:model];
}
// 異步緩存
[cache setObject:array forKey:@"user" withBlock:^{
// 異步回調
NSLog(@"%@", [NSThread currentThread]);
NSLog(@"array緩存完成....");
}];
// 延時讀取
dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.3 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
// 異步讀取
[cache objectForKey:@"user" withBlock:^(NSString * _Nonnull key, id<NSCoding> _Nonnull object) {
// 異步回調
NSLog(@"%@", [NSThread currentThread]);
NSLog(@"%@", object);
}];
});
列印：
2016-06-09 11:35:44.069 YYCache源碼分析[13546:949048] <NSThread: 0x7ffd43f14840>{number = 2, name = (null)}
2016-06-09 11:35:44.069 YYCache源碼分析[13546:949048] array緩存完成....
2016-06-09 11:35:44.386 YYCache源碼分析[13546:949052] <NSThread: 0x7ffd43e01900>{number = 3, name = (null)}
2016-06-09 11:35:44.386 YYCache源碼分析[13546:949052] (
"<UserModel: 0x7ffd44014310>",
"<UserModel: 0x7ffd44014310>"
)
// 緩存實作，預設同時進行記憶體緩存與檔案緩存
- (void)setObject:(id<NSCoding>)object forKey:(NSString *)key {
[_memoryCache setObject:object forKey:key];
[_diskCache setObject:object forKey:key];
}
// 如果隻想記憶體緩存，可以直接調用`memoryCache`對象
YYCache *cache2 = [YYCache cacheWithName:@"mydb"];
[cache2.memoryCache setObject:@24 forKey:@"age"];
NSLog(@"age緩存在記憶體：%d", [cache2.memoryCache containsObjectForKey:@"age"]);
NSLog(@"age緩存在檔案：%d", [cache2.diskCache containsObjectForKey:@"age"]);
2016-06-09 21:23:24.326 YYCache源碼分析[14512:1085375] age緩存在記憶體：1
2016-06-09 21:23:24.326 YYCache源碼分析[14512:1085375] age緩存在檔案：0
4.YYCache.h tips
#if __has_include(<YYCache/YYCache.h>)
#import <YYCache/YYMemoryCache.h>
#import <YYCache/YYDiskCache.h>
#import <YYCache/YYKVStorage.h>
#elif __has_include(<YYWebImage/YYCache.h>)
#import <YYWebImage/YYMemoryCache.h>
#import <YYWebImage/YYDiskCache.h>
#import <YYWebImage/YYKVStorage.h>
#else
#import "YYMemoryCache.h"
#import "YYDiskCache.h"
#import "YYKVStorage.h"
#endif
__has_include：用來檢查Frameworks是否引入某個類，
像YYWebImage已經內建YYCache,如果導入過YYWebImage則無需重新導入YYCache
NS_ASSUME_NONNULL_BEGIN
...
NS_ASSUME_NONNULL_END
接口中 nullable 的是少數,一般都為nonnull,為了防止寫一大堆 nonnull，Foundation供了一對宏NS_ASSUME_NONNULL_BEGIN、NS_ASSUME_NONNULL_END，包在裡面的對象預設加 nonnull 修飾符，如果是nullable的,隻需要把 nullable 的指出來就行
+ (instancetype)new UNAVAILABLE_ATTRIBUTE;
command+滑鼠左鍵UNAVAILABLE_ATTRIBUTE，
發現宏定義#define UNAVAILABLE_ATTRIBUTE __attribute__((unavailable)),
__attribute__是Clang提供的一種源碼注解，友善開發者向編譯器表達某種要求,括号裡是傳達某種指令.
為友善使用，一些常用屬性也被Cocoa定義成宏,
比如UNAVAILABLE_ATTRIBUTE、NS_CLASS_AVAILABLE_IOS(9_0).
unavailable告訴編譯器該方法失效.
在封裝單例或初始化某個類前必須做一些事時,對一些方法禁用是非常不錯的選擇.
還可以給個message提示:
+ (instancetype)alloc __attribute__((unavailable("alloc方法不可用，請用initWithName:")));
- (instancetype)init __attribute__((unavailable("init方法不可用，請用initWithName:")));
- (instancetype)copy __attribute__((unavailable("copy方法不可用，請用initWithName:")));
本文隻是簡單剖析，接下來會分析YYMemoryCache實作原理.