iOS創建自己本地緩存目錄，截圖圖片存儲失敗問題

1. 創建自定義目錄時，fileExistsAtPath 必須判斷是文件目錄

/**
 get absolute iamge cache path
 
 @param imageName file name
 @return absolute path
 */
+ (NSString *)getAbsoluteImageCachePath:(NSString *)imageName {
    NSString *appPackageName = [APP_INFO_DICT objectForKey:@"CFBundleIdentifier"];
    
    NSString *md5ImageName = [self cachedFileNameForKey:imageName];
    NSString *adShowImageDiskPath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, true) firstObject];
    NSString *adShowImageDiskDir = [adShowImageDiskPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@/CZFAdShowImages/", appPackageName]];
    adShowImageDiskPath = [adShowImageDiskDir stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png", md5ImageName]];
    
    NSFileManager *fileManager = [NSFileManager defaultManager];
    if (![fileManager fileExistsAtPath:adShowImageDiskDir]) {
        NSError *error;
        [fileManager createDirectoryAtPath:adShowImageDiskDir withIntermediateDirectories:YES attributes:nil error:&error];
        if (error) {
            NSLog(@"create directory error:%@", error.description);
        }
    }
    
    return adShowImageDiskPath;
}