YYCache源碼分析(一)
文／漢斯哈哈哈（簡書作者）
原文鏈接：http://www.reibang.com/p/b8dcf6634fab
iOS 開發(fā)中總會用到各種緩存，YYCache或許是你最好的選擇窿吩。性能上有優(yōu)勢，用法也很簡單铝侵。作者ibireme曾經(jīng)對比過同類輪子：http://blog.ibireme.com/2015/10/26/yycache/
1.簡單架構(gòu)圖
2.YYCache.h方法分析
@interface YYCache : NSObject
// 讀取當前數(shù)據(jù)庫名稱
@property (copy, readonly) NSString *name;
// memoryCache內(nèi)存緩存，diskCache文件緩存
@property (strong, readonly) YYMemoryCache *memoryCache;
@property (strong, readonly) YYDiskCache *diskCache;
// 可通過下面四種方法來實例化YYCache對象
- (nullable instancetype)initWithName:(NSString *)name;
- (nullable instancetype)initWithPath:(NSString *)path NS_DESIGNATED_INITIALIZER;
+ (nullable instancetype)cacheWithName:(NSString *)name;
+ (nullable instancetype)cacheWithPath:(NSString *)path;
// 禁止通過下面兩個方式實例化對象
- (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温治，第二個法是異步執(zhí)行,異步回調(diào)
- (BOOL)containsObjectForKey:(NSString *)key;
- (void)containsObjectForKey:(NSString *)key withBlock:(nullable void(^)(NSString *key, BOOL contains))block;
// 讀--通過key讀取緩存养铸，第二個法是異步執(zhí)行,異步回調(diào)
- (nullable id<NSCoding>)objectForKey:(NSString *)key;
- (void)objectForKey:(NSString *)key withBlock:(nullable void(^)(NSString *key, id<NSCoding> object))block;
// 增雁芙、改--緩存對象(可緩存遵從NSCoding協(xié)議的對象)轧膘，第二個法是異步執(zhí)行,異步回調(diào)
- (void)setObject:(nullable id<NSCoding>)object forKey:(NSString *)key;
- (void)setObject:(nullable id<NSCoding>)object forKey:(NSString *)key withBlock:(nullable void(^)(void))block;
// 刪--刪除緩存
- (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
這些語法：參考外鏈學習:
NS_DESIGNATED_INITIALIZER
- (instancetype)new attribute((unavailable("new方法不可用，請用initWithName:")));
3.YYCache使用
// 0.初始化YYCache
YYCache *cache = [YYCache cacheWithName:@"mydb"];
// 1.緩存普通字符
[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(shù)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(diào)
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(diào)
NSLog(@"%@", [NSThread currentThread]);
NSLog(@"%@", object);
}];
});
打油酶省：
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>",
"<UserModel: 0x7ffd44014310>",
"<UserModel: 0x7ffd44014310>",
"<UserModel: 0x7ffd44014310>",
"<UserModel: 0x7ffd44014310>",
"<UserModel: 0x7ffd44014310>",
"<UserModel: 0x7ffd44014310>",
"<UserModel: 0x7ffd44014310>",
"<UserModel: 0x7ffd44014310>"
)
// 緩存實現(xiàn)谎碍，默認同時進行內(nèi)存緩存與文件緩存
- (void)setObject:(id<NSCoding>)object forKey:(NSString *)key {
[_memoryCache setObject:object forKey:key];
[_diskCache setObject:object forKey:key];
}
// 如果只想內(nèi)存緩存，可以直接調(diào)用`memoryCache`對象
YYCache *cache2 = [YYCache cacheWithName:@"mydb"];
[cache2.memoryCache setObject:@24 forKey:@"age"];
NSLog(@"age緩存在內(nèi)存：%d", [cache2.memoryCache containsObjectForKey:@"age"]);
NSLog(@"age緩存在文件：%d", [cache2.diskCache containsObjectForKey:@"age"]);
打佣幢骸：
2016-06-09 21:23:24.326 YYCache源碼分析[14512:1085375] age緩存在內(nèi)存：1
2016-06-09 21:23:24.326 YYCache源碼分析[14512:1085375] age緩存在文件：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是否引入某個類蟆淀，
像YYWebImage已經(jīng)集成YYCache,如果導入過YYWebImage則無需重新導入YYCache
NS_ASSUME_NONNULL_BEGIN
@interface YYCache : NSObject
...
- (nullable instancetype)initWithName:(NSString *)name;
...
@end
NS_ASSUME_NONNULL_END
接口中 nullable 的是少數(shù),一般都為nonnull,為了防止寫一大堆 nonnull，F(xiàn)oundation供了一對宏NS_ASSUME_NONNULL_BEGIN澡匪、NS_ASSUME_NONNULL_END熔任，包在里面的對象默認加 nonnull 修飾符，如果是nullable的,只需要把 nullable 的指出來就行
- (instancetype)init UNAVAILABLE_ATTRIBUTE;
+ (instancetype)new UNAVAILABLE_ATTRIBUTE;
<p>
command+鼠標左鍵UNAVAILABLE_ATTRIBUTE唁情，
發(fā)現(xiàn)宏定義#define UNAVAILABLE_ATTRIBUTE __attribute__((unavailable)),
__attribute__是Clang提供的一種源碼注解笋敞，方便開發(fā)者向編譯器表達某種要求,括號里是傳達某種命令.
為方便使用，一些常用屬性也被Cocoa定義成宏,
比如UNAVAILABLE_ATTRIBUTE荠瘪、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方法不可用夯巷，請用initWithName:")));
- (instancetype)init __attribute__((unavailable("init方法不可用，請用initWithName:")));
+ (instancetype)new __attribute__((unavailable("new方法不可用哀墓，請用initWithName:")));
- (instancetype)copy __attribute__((unavailable("copy方法不可用趁餐，請用initWithName:")));
</p>
- (nullable instancetype)initWithPath:(NSString *)path NS_DESIGNATED_INITIALIZER;
NS_DESIGNATED_INITIALIZER 這個宏并不是新面孔，可以使用它標志出像 Swift 一樣的指定構(gòu)造器和便捷構(gòu)造器篮绰。
NS_DESIGNATED_INITIALIZER關(guān)鍵字 意思是最終被指定的初始化方法后雷，在interface只能用一次而且必須以init開頭的方法。
在m文件中吠各，不管init或者其他的初始化方法都要調(diào)用上面的initWithTitle方法初始化臀突，因為我么用到了NS_DESIGNATED_INITIALIZER關(guān)鍵字，不知道明白沒贾漏？http://www.cocoachina.com/bbs/read.php?tid-282223.html
References
http://blog.sunnyxx.com/2016/05/14/clang-attributes/
http://blog.sunnyxx.com/2015/06/12/objc-new-features-in-2015/
