NSCache的使用

Posted 2021-01-04 goodmorningmr

NSCache是苹果公司自己开发的缓存类，其使用方法简单，并且可以设置最大缓存数量，当超出最大数量时自动回收先放入的对象。NSCache是线程安全的，在使用时不用担心因线程而出现的数据错误。

NSCache的接口

- (nullableObjectType)objectForKey:(KeyType)key;  //根据key取出某条数据

- (void)setObject:(ObjectType)obj forKey:(KeyType)key;// 0 cost    //添加某条数据

- (void)setObject:(ObjectType)obj forKey:(KeyType)key cost:(NSUInteger)g;  //添加某条数据并设置其占用的资源数目

- (void)removeObjectForKey:(KeyType)key;    //删除某条数据

- (void)removeAllObjects;  //删除所有数据

@property NSUInteger totalCostLimit;    // 设置缓存大小限制

@property NSUInteger countLimit;    // 设置总条数的限制

@property BOOL evictsObjectsWithDiscardedContent;   //是否自动舍弃那些内存已经被丢弃的对象

- (void)cache:(NSCache *)cache willEvictObject:(id)obj;   //代理方法当对象呗删除时调用

封装的管理器方法

.h中的代码

+ (instancetype)manager;

- (void)addDataArr:(NSArray *)dataArr modelStr:(NSString *)str;

- (NSArray *)getDataWithModelStr:(NSString *)str;
- (void)removeAllObjects;

.m中的代码

@property (nonatomic, strong) NSCache * cache;


+ (instancetype)manager
{
    static CacheManager * manager = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        manager = [[CacheManager alloc] init];
        manager.cache.totalCostLimit = 500;    //设置总缓存数据大小
    });
    return manager;
}

- (NSArray *)getDataResultWithModelStr:(NSString *)str
{
    NSArray * resulr = [self getDataWithModelStr:str];
    if (resulr.count == 0) {
        return nil;
    }
    return resulr;
}

- (void)refreshDataWithArr:(NSArray *)dataArr withStr:(NSString *)modelStr
{
    [self removeObjectForKey:modelStr];
    [self addDataArr:dataArr modelStr:modelStr];
}


//根据传入的model名称信息来添加数据
- (void)addDataArr:(NSArray *)dataArr modelStr:(NSString *)str {
    if (dataArr.count == 0) return;
    for (NSInteger i = 0; i < dataArr.count; i++) {
        [self.cache setObject:dataArr[i] forKey:[NSString stringWithFormat:@"%@%ld", str,i] cost:1];   //添加内容到缓存中，并设置每个对象所占的大小
    }
}

////取出缓存数据
- (NSArray *)getDataWithModelStr:(NSString *)str {
    
    NSMutableArray * dataArr = @[].mutableCopy;
    for (NSInteger i = 0; i < self.cache.countLimit; i++) {
        NSObject * model = [_cache objectForKey:[NSString stringWithFormat:@"%@%ld", str,i]];
        if (model) {
            [dataArr addObject:model];
        }else{
            break;
        }
    }
    return dataArr;
}

//删除某一key值下的所有数据
- (void)removeObjectForKey:(NSString *)key
{
    for (NSInteger i = 0; i < self.cache.countLimit; i++) {
        id model = [_cache objectForKey:[NSString stringWithFormat:@"%@%ld", key,i]];
        if (model) {
            [self.cache removeObjectForKey:[NSString stringWithFormat:@"%@%ld", key,i]];
        }else{
            return;
        }
    }
}

- (void)removeAllObjects
{
    [self.cache removeAllObjects];
}


- (NSCache *)cache
{
    if (!_cache) {
        _cache = [[NSCache alloc] init];
        _cache.delegate = self;
    }
    return _cache;
}