iOS开发-获取文件的MIMEType

有时候我们需要获取文件的MIMEType的信息，比如向服务器上传文件资源时需要将文件资源类型传给服务器，这样就可以判断文件是图片还是音视频，下面就介绍关于获取MIMEType的方法：

- (NSString *)fileMIMETypeURLSessionWithPath:(NSString*)path {
    //1.确定请求路径
    NSURL *url = [NSURL fileURLWithPath:path];
    //2.创建可变的请求对象
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);
    __block NSString *mimeType = nil;
    NSURLSessionTask *task = [[NSURLSession sharedSession] dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        mimeType = response.MIMEType;
        dispatch_semaphore_signal(semaphore);
    }];
    [task resume];
    dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
    return mimeType;
}

//向该文件发送请求,根据请求头拿到该文件的MIMEType
- (NSString *)fileMIMETypeURLConnectionWithPath:(NSString*)path {
    //1.确定请求路径
    NSURL *url = [NSURL fileURLWithPath:path];
    //2.创建可变的请求对象
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    //3.发送请求
    NSHTTPURLResponse *response = nil;
    [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];
    NSString *mimeType = response.MIMEType;
    return mimeType;
}

//调用C语言的API来获得文件的MIMEType ，只能获取本地文件哦，无法获取网络请求来的文件
- (NSString *)fileMIMETypeWithCAPIAtFilePath:(NSString *)path {
    if (![[[NSFileManager alloc] init] fileExistsAtPath:path]) {
        return nil;
    }
    
    CFStringRef UTI = UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension, (__bridge CFStringRef)[path pathExtension], NULL);
    CFStringRef MIMEType = UTTypeCopyPreferredTagWithClass (UTI, kUTTagClassMIMEType);
    CFRelease(UTI);
    if (!MIMEType) {
        return @"application/octet-stream";
    }
    return (__bridge NSString *)(MIMEType);
}