AFNetworking Multipart Form Requ

问题描述

前不久我在开发公司的一款SDK的过程中，遇到过发生在AFNetworking使用multipart form request来上传文件的内存泄漏问题，调试了半天，后来终于发现问题在于用AFHTTPRequestSerializer的multipartFormRequestWithMethod:URLString:parameters:constructingBodyWithBlock:error:方法来构建multipart form request，会产生内存泄漏。基本上泄露内存的大小，跟上传文件的大小差不多，我没有深入AFHTTPRequestSerializer的源码，具体原因我不清楚，Google也没搜到类似的情况。

leak.png

• 说明: 截图中的类名都以AS开头，因为这是SDK开发，我直接将AFNetworking的源码放在了SDK项目里面，然后给AFNetworking的类前缀加上了AS从而变成了ASAFNetworking，这样是为了避免集成了SDK的app同时也在用AFNetworking，从而产生类冲突。后期会考虑砍掉AFNetworking，自己基于NSURLSession写一套HTTP框架。

解决方案

之后我把用AFHTTPRequestSerializer构造multipart form request的代码，用原生的方式取代，内存泄露问题解决。整个构造multipart form request的代码用了Stack Overflow上搜的一段代码，代码如下:

// configure the request
NSURL *url = @"https://api-url";
NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url];
[request setHTTPMethod:@"POST"];

NSString *boundary = [self generateBoundaryString];

// set content type
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@", boundary];
[request setValue:contentType forHTTPHeaderField: @"Content-Type"];

// create body
NSString *filePath = @"file-path";
NSData *httpBody = [self createBodyWithBoundary:boundary parameters:nil paths:@[filePath] fieldName:@"file"];
request.HTTPBody = httpBody;

上述代码中用到的两个方法：

- (NSData *)createBodyWithBoundary:(NSString *)boundary
                        parameters:(NSDictionary *)parameters
                             paths:(NSArray *)paths
                         fieldName:(NSString *)fieldName {
    NSMutableData *httpBody = [NSMutableData data];

    // add params (all params are strings)
    [parameters enumerateKeysAndObjectsUsingBlock:^(NSString *parameterKey, NSString *parameterValue, BOOL *stop) {
        [httpBody appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
        [httpBody appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"\r\n\r\n", parameterKey] dataUsingEncoding:NSUTF8StringEncoding]];
        [httpBody appendData:[[NSString stringWithFormat:@"%@\r\n", parameterValue] dataUsingEncoding:NSUTF8StringEncoding]];
    }];

    // add image data
    for (NSString *path in paths) {
        NSString *filename  = [path lastPathComponent];
        NSData   *data      = [NSData dataWithContentsOfFile:path];
        NSString *mimetype  = [self mimeTypeForPath:path];

        [httpBody appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];
        [httpBody appendData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"%@\"; filename=\"%@\"\r\n", fieldName, filename] dataUsingEncoding:NSUTF8StringEncoding]];
        [httpBody appendData:[[NSString stringWithFormat:@"Content-Type: %@\r\n\r\n", mimetype] dataUsingEncoding:NSUTF8StringEncoding]];
        [httpBody appendData:data];
        [httpBody appendData:[@"\r\n" dataUsingEncoding:NSUTF8StringEncoding]];
    }

    [httpBody appendData:[[NSString stringWithFormat:@"--%@--\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];

    return httpBody;
}

- (NSString *)generateBoundaryString {
    return [NSString stringWithFormat:@"Boundary-%@", [[NSUUID UUID] UUIDString]];
}

最后leak工具一片绿...好像哪里不对，怎么就绿了呢😂...

non-leak.png