Question

some codes in httpController.h like this:

@interface httpController:NSObject{
  ...
  NSMutableData *receivedData;
}
@property (nonatomic,retain) NSMutableData *receivedData;

and some codes in httpController.m file like this:

@implementation httpController
@synthesize receivedData;
...
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
  [receivedData setLength:0];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data               
{
  if (!receivedData) {
      receivedData = [[NSMutableData alloc] init];
  }
  [receivedData appendData:data];  
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {

}

Then I want using the receivedData in the main.m file, like this:

int main(int argc, const char *argv[])
{
   HttpController *httpController = [[HttpController alloc] init];
   NSURLRequest *request = ...;
   NSURLConnection *connetion = ...;
   if(connection)
   {
     NSMutableData *_receviedData = httpController.receivedData;
     NSString * dataString = [[[NSString alloc] initWithData:_receviedData encoding:NSUTF8StringEncoding] autorelease]; 
     NSLog(@"%@",dataString);
   }
   [[NSRunLoop currentRunLoop] run];
}

But i found that in the main() function, the value of _receivedData is empty, and there is noting outputted. Anyone can tell me What’s wrong about it?

Answer 1

+connectionWithRequest:delegate: runs asynchronously. It looks like it’s not finishing the connection before returning, which is why you don’t see any data. Try +sendSynchronousRequest:returningResponse:error: instead, as this will block the thread until the connection finishes.

There’s no need for a HttpController/delegate when using +sendSynchronousRequest:returningResponse:error: either. Here’s how to do it:

int main(int argc, const char *argv[])
{
    NSURL           *url        = [NSURL URLWithString:@"http://www.yahoo.com/"];
    NSURLRequest    *request    = [NSURLRequest requestWithURL:url];
    NSURLResponse   *response   = nil;
    NSError         *error      = nil;

    // This blocks "this" thread until it's done.
    NSData          *data       = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

    if (!data)
    {
        NSLog(@"Error: %@", error);
    }
    else
    {
        NSString *dataString = [[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding] autorelease];
        NSLog(@"%@", dataString);
    }
}

If you don’t want to block the thread, then +connectionWithRequest:delegate: is the way to go. But you’ll have to write your code differently, and should read the docs.