一般请求的话是这样

     AFHTTPSessionManager *session = [AFHTTPSessionManager manager];
    session.responseSerializer.acceptableContentTypes = [NSSet setWithObjects:@"text/html", nil];
    [session POST:@"" parameters:@"" progress:nil success:nil failure:nil];

但是今天遇到个不管怎么样parameters都传不到服务器那边，而后台那边给我的解释是传输用[request setHTTPBody:data];
而 afn 2.0 是这样的

NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:url]];
[request setHTTPMethod:@"POST"];
[request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
NSError *error;
NSData *jsonData = [NSJSONSerialization dataWithJSONObject:parameters
   options:0
     error:&error];
NSString *jsonString = [[NSString alloc] initWithData:jsonData encoding:NSUTF8StringEncoding];

// And finally, add it to HTTP body and job done.
[request setHTTPBody:[jsonString dataUsingEncoding:NSUTF8StringEncoding]];

AFHTTPRequestOperationManager *manager = [AFHTTPRequestOperationManager manager];
manager.requestSerializer.timeoutInterval=[[[NSUserDefaults standardUserDefaults] valueForKey:@"timeoutInterval"] longValue];
manager.requestSerializer = [AFJSONRequestSerializer serializer];
AFHTTPRequestOperation *operation = [manager HTTPRequestOperationWithRequest:request progress:nil success:^(NSURLSessionTask *task, id responseObject) {
    NSLog(@"Reply JSON: %@", responseObject);

    }
} failure:^(NSURLSessionTask *operation, NSError *error) {
    NSLog(@"Error: %@, %@, %@, %@, %@", error, operation.responseObject, operation.responseData, operation.responseString, operation.request);

}];
[operation start];

但是3.0弃用了AFHTTPRequestOperationManager,那么怎么才能用呢？
1.用系统NSURLConnection 请求

      NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:@"url"]];
        [request setHTTPBody:data];
        [request setHTTPMethod:@"POST"];
        [request setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
    
        NSURLConnection *theConnection=[[NSURLConnection alloc] initWithRequest:request delegate:self];
    
    
        if (theConnection) {
            NSLog(@"connected");
            receivedData=[[NSMutableData alloc]init];
        } else {
    
            NSLog(@"not connected");
        }
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [receivedData setLength:0];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [receivedData appendData:data];
    NSString* responseString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"response: %@",responseString);
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"Succeeded! Received %lu data",(unsigned long)[receivedData length]);
    NSString* responseString = [[NSString alloc] initWithData:receivedData encoding:NSUTF8StringEncoding];
    NSLog(@"response: %@",responseString);
    NSError *myError = nil;
    NSDictionary *res = [NSJSONSerialization JSONObjectWithData:receivedData options:NSJSONReadingMutableLeaves error:&myError];
    NSLog(@"%@",res);
}

2.用不习惯系统没关系，其实afn3.0 也有提供api给我们调用，但是这个是我一直没接触过的AFURLSessionManager。

 AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]];
    
    NSMutableURLRequest *req = [[AFJSONRequestSerializer serializer] requestWithMethod:@"POST" URLString:@"url" parameters:nil error:nil];
    
    req.timeoutInterval= [[[NSUserDefaults standardUserDefaults] valueForKey:@"timeoutInterval"] longValue];
    [req setValue:@"application/json" forHTTPHeaderField:@"Content-Type"];
    [req setValue:@"application/json" forHTTPHeaderField:@"Accept"];
    [req setHTTPBody:da];
    
    [[manager dataTaskWithRequest:req completionHandler:^(NSURLResponse * _Nonnull response, id  _Nullable responseObject, NSError * _Nullable error) {
        
        if (!error) {
            NSLog(@"Reply JSON: %@", responseObject);
        } else {
            NSLog(@"Error: %@, %@, %@", error, response, responseObject);
        }
    }] resume];