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//获取文件夹大小
NSFileManager *mgr = [NSFileManager defaultManager];
NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)lastObject];
//文件夹的属性
//NSDictionary *attrs = [mgr attributesOfItemAtPath:caches error:nil];
//获得文件夹的属性，文件夹没有大小遍历所有文件加起来活儿文件的大小
//获取caches里面的所有内容
//NSArray *contents =  [mgr contentsOfDirectoryAtPath:caches error:nil];
NSArray *subPaths = [mgr subpathsAtPath:caches];
NSInteger totalByteSize = 0;
for (NSString *subPath in subPaths)
{
    NSString *fullPath = [caches stringByAppendingPathComponent:subPath];
    //判断是文件还是文件夹
    BOOL dir = NO;
    [mgr fileExistsAtPath:fullPath isDirectory:&dir];
    if (dir == NO)
    {
        //文件
        NSDictionary *attrs = [mgr attributesOfItemAtPath:fullPath error:nil];
        NSInteger byteSize = [attrs[NSFileSize] integerValue];
        
        totalByteSize += byteSize;
        
    }
}
NSLog(@"%ld",totalByteSize);

、、、
清缓存
、、、
//删除该文件夹
[mgr removeItemAtPath:caches error:nil];
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