如何在NSDocumentDirectory内新建一个文件夹

- (NSString *)pathToPatientPhotoFolder {
    NSString *documentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,
                                                                    NSUserDomainMask,
                                                                    YES) lastObject];
    NSString *patientPhotoFolder = [documentsDirectory stringByAppendingPathComponent:@"patientPhotoFolder"];

    // Create the folder if necessary
    BOOL isDir = NO;
    NSFileManager *fileManager = [[NSFileManager alloc] init];
    if (![fileManager fileExistsAtPath:patientPhotoFolder
                           isDirectory:&isDir] && isDir == NO) {
        [fileManager createDirectoryAtPath:patientPhotoFolder
               withIntermediateDirectories:NO
                                attributes:nil
                                     error:nil];
    }
    return patientPhotoFolder;
}

//删除文件
NSString *patientPhotoFolder = [[NSFileManager defaultManager] pathToPatientPhotoDirectory];
NSArray *contents = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:patientPhotoFolder error:nil];
for (NSString *filename in contents)  {
    [[NSFileManager defaultManager] removeItemAtPath:[patientPhotoFolder stringByAppendingPathComponent:filename] error:NULL];
}