ios - Asynchronous loading of images? -


how can load images asynchronously? i'm doing (borrowed open source code loading image thumbnail):

- (uiimage*)thumbnaillistview:(thumbnaillistview*)thumbnaillistview                  imageatindex:(nsinteger)index {     nsurl* url = [nsurl urlwithstring:[recommendedarray objectatindex:index]] ;  //  [[cell grid_image] setimage:[uiimage imagewithdata:[nsdata datawithcontentsofurl:url]]];    nsstring *docpath = [nssearchpathfordirectoriesindomains(nsdocumentdirectory, nsuserdomainmask, yes) objectatindex:0]; bool isimageloaded = yes; uiimage *bookimage = [uiimage imagewithcontentsoffile:[nsstring stringwithformat:@"%@/%@", docpath, [[recommendedarray objectatindex:index] lastpathcomponent]]];  if(bookimage == nil)     isimageloaded = no;  if(!isimageloaded){     uiimage *thumbnailimage =[uiimage imagenamed:@"app-icon-144x144.png"];} else{     uiimage *thumbnailimage = [uiimage imagewithdata:[nsdata datawithcontentsofurl:[nsurl urlwithstring:[nsstring stringwithformat:@"%@",[recommendedarray objectatindex:index]]]]];       return thumbnailimage;  }    }

i tried adding following method, it's producing error nsurl:

dispatch_queue_t imageloadqueue = dispatch_queue_create("com.g.load", null);  dispatch_async(imageloadqueue, ^{     //wait 5 seconds...     usleep(1000000);      nsarray *docpath = [nssearchpathfordirectoriesindomains(nsdocumentdirectory, nsuserdomainmask, yes) objectatindex:0];          for(int k=0; k < [images count];k++){         nslog(@"loading %d image", k);         nsstring *imgurl = [images objectatindex:k];         nsdata *imgdata = [[nsdata alloc] initwithcontentsofurl:[nsurl urlwithstring:imgurl]];         [imgdata writetofile:[nsstring stringwithformat:@"%@/%@", docpath, [imgurl lastpathcomponent]] atomically:yes];     }      [[self collectionview] reloaddata];     nslog(@"done images"); });

error

[nsurl length]: unrecognized selector sent instance 0x12ea7240 2013-04-18 11:18:35.456 assamkart[3084:14d03] *** terminating app due uncaught exception 'nsinvalidargumentexception', reason: '-[nsurl length]: unrecognized selector sent instance 0x12ea7240'

inside method-> 

- (uiimage*)thumbnaillistview:(thumbnaillistview*)thumbnaillistview                      imageatindex:(nsinteger)index

use this->

nsurlconnection *ansurlconnection= [[nsurlconnection alloc]initwithrequest:<#(nsurlrequest *)#> delegate:<#(id)#> startimmediately:<#(bool)#>];

and inside delegate

- (void)connectiondidfinishloading:(nsurlconnection *)connection; image data , implement logic , here u shall call again the

- (uiimage*)thumbnaillistview:(thumbnaillistview*)thumbnaillistview                      imageatindex:(nsinteger)index

method recursively till recommendedarray exhausted.


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