ios - How to edit a UITableViewCell in a completion block from a method called inside the delegate method cellForRowAtIndexPath: -

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in uitableview delegate method cellforrowatindexpath:(nsindexpath *)indexpath, want set image cell imageview. if image not available, download , set asynchronously in complete block. problem because cells reusable, maybe when completion block called, cell may not exist anymore. how can update cell when completion block called? or way ok?

- (uitableviewcell *)tableview:(uitableview *)tableview cellforrowatindexpath:(nsindexpath *)indexpath {     friendtableviewcell *cell = [self.tableview dequeuereusablecellwithidentifier:@"friend cell"];      friend *friend = self.friends[indexpath.row];      if (friend.picture) {         cell.userprofileimageview.image = [uiimage imagewithdata:picturedata];     } else {         cell.userprofileimageview.image = nil;          nsurl *pictureurl = [nsurl urlwithstring:[nsstring stringwithformat:@"https://graph.facebook.com/%@/picture?type=normal&return_ssl_res", friend.facebookid]];          nsurlrequest *urlrequest = [nsurlrequest requestwithurl:pictureurl];          // run network request asynchronously         [nsurlconnection sendasynchronousrequest:urlrequest                                            queue:[nsoperationqueue mainqueue]                                completionhandler:^(nsurlresponse *response, nsdata *data, nserror *connectionerror) {              if (connectionerror == nil && data != nil) {                  friend.picture = data;                  friendtableviewcell *celltoupdate = (friendtableviewcell *)[self.tableview cellforrowatindexpath:indexpath];                  celltoupdate.userprofileimageview.image = [uiimage imagewithdata:data];              }          }];     }      return cell; }

in completion handler ask table reload affected row. data model has picture, update correctly. protects against cells being off screen result in noop(). when scroll picture in data model.

so like:

[nsurlconnection sendasynchronousrequest:urlrequest                                            queue:[nsoperationqueue mainqueue]                                completionhandler:^(nsurlresponse *response, nsdata *data, nserror *connectionerror) {              if (connectionerror == nil && data != nil) {                  friend.picture = data;                  self.tableview reloadrowsatindexpaths:@[indexpath]                                       withrowanimation:uitableviewrowanimationnone]              }          }];

if decide run asynchronous request in non main thread, need schedule row reload on main thread.


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