CODEWITHSUNDEEP
objective-cdownloadasihttprequest
Aqueel
Aqueel

Reputation: 1246

ASIHttp Synchronous request is running delegate methods after returning

I am trying to download a file from a server. My code is following. In didFinishLaunchingWithOptions method, I create a new thread using detachNewThreadSelector which runs the following code. 

NSString *destPath = [self.home_dir_path stringByAppendingPathComponent:[NSString stringWithFormat:@"_%@",content_data_file_name]];
[ContentBO downloadFile:destPath  content_name:content_data_file_name];
if([self updatesAvailable]){
    //update content
}else{
    //launch app
}

My code for downloadFile is:

@try{
    NSString *url = [NSString stringWithFormat:@"%@/%@",ServerURL,content_name];
    NSLog(@"downloading URL is: %@",url);
    self.request = [ASIHTTPRequest requestWithURL:[NSURL URLWithString:[url stringByAddingPercentEscapesUsingEncoding:NSASCIIStringEncoding]]];
    [self.request setRequestMethod:@"GET"];
    [self.request setDownloadDestinationPath:destFilePath]; 
    NSLog(@"destination path is: %@",destFilePath);
    [self.request setTimeOutSeconds:30];

    [self.request setDelegate:self];
    [self.request startSynchronous];

    NSError *error = [self.request error];
    NSData *receivedData = nil;

    if (!error) {
        isSuccess = YES;
        self.responseStr = [request responseString];
        receivedData = [NSData dataWithData:[self.request responseData]];
    }
    else {
        isSuccess = NO;
        NSLog(@"The following error occurred: %@", error);
    }
}@catch(NSException *e){
    NSLog(@"exception occured.");
}

What my understanding about synchronous call is that this is a blocking call and control should not go below

[ContentBO downloadFile:destPath  content_name:content_data_file_name];

until control is out of requestFinished method of ASIHTTPRequestDelegate. In my case what happening is that the control is simultaneously executing code in requestFinished and below

[ContentBO downloadFile:destPath  content_name:content_data_file_name];

But I don't want the control to go below [ContentBO downloadFile...] before coming out of requestFinished method.

Upvotes: 3

Views: 443

Answers (2)

Jamal Zafar
Jamal Zafar

Reputation: 2189

In one of my projects the app had to do heavy server side data syncing. In that process one operation should had start after the successful execution of it's previous process and I was using ASIHttp synchronous requests in that. I was facing the same issue you mentioned, so to tackle it I used NSCondiiton. All it requires that you lock the thread after you call: [self.request startSynchronous];. When the requests delegate method is called after the exection of the request, issue a signal command, and the next line of the code after the thread lock statement will be executed. Here is a rough example:

//declare a pointer to NSCondition in header file: 
    NSCondition *threadlock;


-(id) init 
{
      threadlock = [[NSCondition alloc] init];  //release it in dealloc
}


-(void)downLoadFile 
{
  [thread lock];

  //your request code

  [self.request setDidFinishSelector:@selector(downLoadFileRequestDone:)];  
  [self.request setDidFailSelector:@selector(downLoadFileRequestWentWrong:)];
  [self.request startSynchronous];
  [thread wait];
  //the lines here will be executed after you issue a signal command in the request delegate method
  [thread unlock];
}

-(void) downLoadFileRequestDone:(ASIHTTPRequest *)request
 {
  [thread lock];
  //perform desire functionality
  //when you are done call:
  [thread signal];
  [thread unlock];
}

It worked perfect for me... hope it will help.

Upvotes: 0

JosephH
JosephH

Reputation: 37495

The requestFinished delegate call is run on the main thread asynchronously, and your code is not running on the main thread, so it is expected that both would run at the same time.

However, as you are using synchronous requests why not remove the contents of requestFinished and put the code after the 'startSyncronous' line? You are guaranteed the request has finished when startSynchronous returns.

Upvotes: 1

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