ios 怎样判断某个文件是否存在

- (void)createFileDirectories
{
// 判断存放音频、视频的文件夹是否存在，不存在则创建对应文件夹
NSFileManager *fileManager = [NSFileManagerdefaultManager];
BOOL isDir = FALSE;
BOOL isDirExist = [fileManager fileExistsAtPath:DOCUMENTS_FOLDER_AUDIOisDirectory:&isDir];

if(!(isDirExist && isDir))
{
BOOL bCreateDir = [fileManager createDirectoryAtPath:DOCUMENTS_FOLDER_AUDIOwithIntermediateDirectories:YESattributes:nilerror:nil];
if(!bCreateDir){
NSLog(@"Create Audio Directory Failed.");
}
NSLog(@"%@",DOCUMENTS_FOLDER_AUDIO);
}

isDir = FALSE;
isDirExist = [fileManager fileExistsAtPath:DOCUMENTS_FOLDER_VEDIOisDirectory:&isDir];

if(!(isDirExist && isDir)){
BOOL bCreateDir = [fileManager createDirectoryAtPath:DOCUMENTS_FOLDER_VEDIOwithIntermediateDirectories:YESattributes:nilerror:nil];
if(!bCreateDir){
NSLog(@"Create Audio Directory Failed.");
}
NSLog(@"%@",DOCUMENTS_FOLDER_VEDIO);
}
}