iOS 缓存文件管理

iOS 应用文件缓存一般分为2种情况：用户自己缓存，第三方库SDWebImage的缓存；

对缓存大小的统计主要依赖于iOS提供的类NSFileManager来做；

一、单个文件计算大小

-(long long)fileSizeAtPath:(NSString *)path{
    NSFileManager *fileManager=[NSFileManager defaultManager];
    if([fileManager fileExistsAtPath:path]){
        long long size=[fileManager attributesOfItemAtPath:path error:nil].fileSize;
        return size;
    }
    return 0;
}

二、文件夹大小计算

-(float)folderSizeAtPath:(NSString *)path{
    NSFileManager *fileManager=[NSFileManager defaultManager];
    NSString *cachePath=[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
    cachePath=[cachePath stringByAppendingPathComponent:path];
    long long folderSize=0;
    if ([fileManager fileExistsAtPath:cachePath])
    {
        NSArray *childerFiles=[fileManager subpathsAtPath:cachePath];
        for (NSString *fileName in childerFiles)
        {
            NSString *fileAbsolutePath=[cachePath stringByAppendingPathComponent:fileName];
            long long size=[self fileSizeAtPath:fileAbsolutePath];
            folderSize += size;
            NSLog(@"fileAbsolutePath=%@",fileAbsolutePath);

        }
        //SDWebImage框架自身计算缓存的实现
        folderSize+=[[SDImageCache sharedImageCache] getSize];
        return folderSize/1024.0/1024.0;
    }
    return 0;
}

三、文件清除
1、用户自身文件大小清除
利用NSFileManager API进行文件操作

-(void)clearCache:(NSString *)path{
    NSString *cachePath=[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];
    cachePath=[cachePath stringByAppendingPathComponent:path];
    NSFileManager *fileManager=[NSFileManager defaultManager];
    if ([fileManager fileExistsAtPath:cachePath]) {
        NSArray *childerFiles=[fileManager subpathsAtPath:cachePath];
        for (NSString *fileName in childerFiles) {
            //如有需要，加入条件，过滤掉不想删除的文件
            NSString *fileAbsolutePath=[cachePath stringByAppendingPathComponent:fileName];
            NSLog(@"fileAbsolutePath=%@",fileAbsolutePath);
            [fileManager removeItemAtPath:fileAbsolutePath error:nil];
        }
    }
}

2、SDWebImage框架自己实现了清理缓存操作，我们可以直接调用。

-(void)clearCacheSDImageCache {
    [[SDImageCache sharedImageCache] cleanDisk];
}

接口说明

1、OC中获取文件属性(Attributes)的方法，获得所给路径(path)的所有“文件属性(fileAttributes),返回一个字典(NSDictionary)来存储,即以键值对的形式存储；

- (nullable NSDictionary<NSFileAttributeKey, id> *)attributesOfItemAtPath:(NSString *)path error:(NSError **)error NS_AVAILABLE(10_5, 2_0);

返回属性字典的属性列表：

//如下属性可以使用点语法获取
Printing description of dic:
{
    NSFileCreationDate = "2016-10-18 10:12:47 +0000";
    NSFileExtensionHidden = 0;
    NSFileGroupOwnerAccountID = 501;
    NSFileGroupOwnerAccountName = mobile;
    NSFileModificationDate = "2016-10-18 10:12:48 +0000";
    NSFileOwnerAccountID = 0;
    NSFileOwnerAccountName = root;
    NSFilePosixPermissions = 420;
    NSFileProtectionKey = NSFileProtectionNone;
    NSFileReferenceCount = 1;
    NSFileSize = 12624777;
    NSFileSystemFileNumber = 6841436;
    NSFileSystemNumber = 16777219;
    NSFileType = NSFileTypeRegular;
}

2、OC中获取文件系统属性

获得所给路径(path)所在“文件系统的属性,返回一个字典(NSDictionary)来存储,即以键值对的形式存储

- (nullable NSDictionary<NSFileAttributeKey, id> *)attributesOfFileSystemForPath:(NSString *)path error:(NSError **)error NS_AVAILABLE(10_5, 2_0);

返回属性字典的属性列表：

Printing description of dicc:
{
    NSFileSystemFreeNodes = 903996;
    NSFileSystemFreeSize = 3702767616;
    NSFileSystemNodes = 3128248;
    NSFileSystemNumber = 16777219;
    NSFileSystemSize = 12813312000;
}

//model
//获得所给文件路径所在文件系统的属性
NSDictionary *attrs = [fm attributesOfFileSystemForPath:file error:nil];

//取出文件系统的属性中NSFileSystemSize键所对应的值,即系统硬盘已经存储的大小
 NSNumber *systemSize = attrs[NSFileSystemSize];
 NSNumber *systemFreeSize = attrs[NSFileSystemFreeSize];  

文件大小获取方式的优化方案

//需要引入头文件
#import <sys/stat.h>

- (void)fileSize {
    struct stat statbuf;
    const char *cpath = [@"pa" UTF8String];
    if (cpath && stat(cpath, &statbuf) == 0) {
        NSNumber *fileSize = [NSNumber numberWithUnsignedLongLong:statbuf.st_size];
        NSDate *modificationDate = [NSDate dateWithTimeIntervalSince1970:statbuf.st_mtime];
        NSDate *creationDate = [NSDate dateWithTimeIntervalSince1970:statbuf.st_ctime];
        // etc
    }
}

ios 设备磁盘剩余空间统计

/// Free disk space in bytes.
static int64_t _KKeyDiskSpaceFree() {
    NSError *error = nil;
    NSDictionary *attrs = [[NSFileManager defaultManager] attributesOfFileSystemForPath:NSHomeDirectory() error:&error];
    if (error) return -1;
    int64_t space =  [[attrs objectForKey:NSFileSystemFreeSize] longLongValue];
    if (space < 0) space = -1;
    return space;
}

注：1k = 1024 byte,但是硬盘上的换算是1K=1000字节