setbackground loading with do while loop

Question

i am working on an application where i check for url using following code.

-(void)exists
{
    NSString *strImg = @"some url";


    NSURL *aImgUrl = [NSURL URLWithString:strImg];

    NSMutableURLRequest *imgRequest = [NSMutableURLRequest requestWithURL:strImg];
    [imgRequest setHTTPMethod:@"HEAD"];

    imgConnection = [NSURLConnection connectionWithRequest:imgRequest delegate:self];
}

This is what i do when i get response.

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{

    if ([(NSHTTPURLResponse *)response statusCode] == 200)
    {
        // url exists
        appDel.isExists = TRUE;
        temp = FALSE;
        [self loadData];
        NSLog(@"%ld",(long)[(NSHTTPURLResponse *)response statusCode]);
    }
    else if([(NSHTTPURLResponse*)response statusCode] == 404)
    {
        //url does not exists
        appDel.isExists = FALSE;
        temp = TRUE;
        [self loadData];
        NSLog(@"%ld",(long)[(NSHTTPURLResponse *)response statusCode]);
    }
}

This is my load data code

-(void)loadData
{


    result = FALSE;

    isReqSent = FALSE;

    do
    {
        if (appDel.isExists == TRUE)
        { 
            NSURL *aTxtUrl = [NSURL URLWithString:apiText];
            NSURL *aImgUrl = [NSURL URLWithString:apiImage];

            NSURLRequest *imgRequest = [NSURLRequest requestWithURL:aImgUrl];
            NSURLRequest *txtRequest = [NSURLRequest requestWithURL:aTxtUrl];

           [NSURLConnection sendAsynchronousRequest:txtRequest queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError)
             {
                 if (data)
                 {
                         NSString *strTxt = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
                         [lblTime setText:strTxt];
                          [policyImgWebView loadRequest:imgRequest];

                         result = TRUE;                     
                 }

             }];

        }

        if (result)
        {
            appDel.isExists = TRUE;
        }
        else
        {
            if(!isReqSent)
            {
                NSString *soapMessage = @"my soap message";

                NSString *soapAction = @"my soap url";


                [objWebServiceParser xmlParsing:soapMessage :soapAction :Number];
                isReqSent = TRUE;
            }

            }
        if (temp)
        {
            dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
                [self backgroundProcess];
            });
        }

    } while (result == FALSE);

This is my background Process

-(void)backgroundProcess
{

    NSString *strImg = @"some url";

    NSURL *aImgUrl = [NSURL URLWithString:apiImage];

    NSMutableURLRequest *imgRequest = [NSMutableURLRequest requestWithURL:aImgUrl];
    [imgRequest setHTTPMethod:@"HEAD"];

    imgConnection = [NSURLConnection connectionWithRequest:imgRequest delegate:self];

}

i do not know where i am doing wrong, can any one guide me?

i want background process to keep running until it gets data, when data received appdel.isExists gets true & gets on main thread to update ui.

I tried GCD & performSelectorInTheBackground but i am not getting it right & i get NSThread fail error 35.

It worked with NSURLSessionDownloadTask but still looking for better option.

Yes when i process to background i do not get response in NSURLConnection Delegate Methods. — Jaymin Raval
– Jaymin Raval, Commented Feb 25, 2014 at 13:39
yes @AkshitZaveri but in background (keep checking until url is valid, as soon as it`s valid load it) — Jaymin Raval
– Jaymin Raval, Commented Feb 27, 2014 at 5:05

Kapil Choubisa · Accepted Answer · 2014-02-26 09:06:53Z

2

Don't call NSURLConnection in background. As NSURLConnection will work automatically. As you are not sending asynchronous request it will work in background and won't hang your main thread. In your load data remove dispatch. You have:

if (temp)
    {
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0), ^{
            [self backgroundProcess];
        });
    }

make it:

if (temp)
    {
        [self backgroundProcess];
    }

You don't need to use dispatch.

answered Feb 26, 2014 at 9:06

Kapil Choubisa

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2 Comments

Jaymin Raval Over a year ago

then do while loop consumes lots of memory

Kapil Choubisa Over a year ago

Memory and Perform task in background doesn't have any relation. Memory is a total different thing. Are you using ARC?

Akshit Zaveri · Accepted Answer · 2014-02-28 03:21:56Z

To load the image in your UIImageView from server, you can use below frameworks.

SDWebImage

You get completionBlock, progressBlock & many more properties that you can use to update your UI. It will notify you in blocks, then you can update whatever you want on UI.

Sample:

It's as simple as this code to just load image if the imageURL is valid (It's your case)

UIImageView *imageView;
[imageView setImageWithURL:[NSURL URLWithString:YOUR_URL]];

And it's also have rich methods like below

UIImageView *imageView;
[imageView setImageWithURL:[NSURL URLWithString:YOUR_URL] 
           placeholderImage:[UIImage imageNamed:@"placeholder.png"]
           completed:^(UIImage *image, NSError *error, SDImageCacheType cacheType) 
           {
               // in "image" you'll get the downloaded image from the URL
               ... completion code here ...

           }];

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