ios - App crashes with 'NSRangeException' when library is empty -

i using code latest photo cameraroll:

- (void) getthelatestphoto{         alassetslibrary *cameraroll = [[alassetslibrary alloc] init];         [cameraroll enumerategroupswithtypes:alassetsgroupsavedphotos usingblock:^(alassetsgroup *images, bool *stop) {             [images setassetsfilter:[alassetsfilter allphotos]];             [images enumerateassetsatindexes:[nsindexset indexsetwithindex:[images numberofassets] - 1] options:0 usingblock:^(alasset *result, nsuinteger index, bool *stop)              {                  if (result) {                       alassetrepresentation *rep = [result defaultrepresentation];                      self.sharingimage = [uiimage imagewithcgimage:[rep fullscreenimage]];                  }              }];         }                                 failureblock: ^(nserror *error) {                                     nslog(@"an error occured: %@",error);                                 }];     } 

as is, if library cameraroll empty, app crash error:

terminating app due uncaught exception 'nsrangeexception', reason: 'indexset count or lastindex must not exceed -numberofassets' 

i understand indexset higher numberofassets due this:

[images enumerateassetsatindexes:[nsindexset indexsetwithindex:[images numberofassets] - 1] 

at point question "where put condition allow me check if assets zero?"

if cameraroll has more zero, let code continue, if count zero, handle issue way oppose let crash:

uialertview *alert = [[uialertview alloc]initwithtitle:@"" message:@"sorry, there no photo in camera roll" delegate:nil cancelbuttontitle:@"ok" otherbuttontitles:nil, nil]; [alert show]; 

thanks help!

add if([images numberofassets]>0) before enumerateassetsatindexes line , continue code...

or if([images numberofassets]<=0)

uialertview *alert = [[uialertview alloc]initwithtitle:@"" message:@"sorry, there no photo in camera roll" delegate:nil cancelbuttontitle:@"ok" otherbuttontitles:nil, nil]; [alert show];