ios - Optimizing an array of UIImages -

so i'm building app user takes pictures of themselves, saves them camera roll, , i'm saving references asset urls display them in app. @ first model seemed work fine, took more , more pictures started receiving memory warnings , crashed. there better way approach this?

this how load saved photos @ launch of app (which freezes app 10 seconds depending on how many being loaded):

- (void) loadphotosarray {     _photos = [[nsmutablearray alloc] init];      nsdata* data = [[nsuserdefaults standarduserdefaults] objectforkey: @"savedimages"];     if (data)     {         nsarray* storedurls = [[nsarray alloc] initwitharray: [nskeyedunarchiver unarchiveobjectwithdata: data]];          // reverse array         nsarray* urls = [[storedurls reverseobjectenumerator] allobjects];          (nsurl* asseturl in urls)         {             // block handle image handling success             alassetslibraryassetforurlresultblock resultblock = ^(alasset *myasset)             {                 alassetrepresentation *rep = [myasset defaultrepresentation];                 cgimageref iref = [rep fullresolutionimage];                 if (iref) {                     uiimage* tempimage = [uiimage imagewithcgimage:iref];                     uiimage* image = [[uiimage alloc] initwithcgimage: tempimage.cgimage scale: 1.0 orientation: uiimageorientationright];                      // set image in imageview                     [_photos addobject: image];                     [[nsnotificationcenter defaultcenter] postnotificationname: @"photoschanged" object: self];                 }             };              // handles failure of getting image             alassetslibraryaccessfailureblock failureblock  = ^(nserror *myerror)             {                 nslog(@"can't image - %@",[myerror localizeddescription]);             };              // load image call appropriate block             alassetslibrary* assetslibrary = [[alassetslibrary alloc] init];             [assetslibrary assetforurl: asseturl                            resultblock: resultblock                           failureblock: failureblock];         }     }     else     {         nslog(@"photo storage empty");     } } 

and saving photos:

- (void) addimagetophotos: (uiimage*)image {     // store image @ front of array     nsmutablearray* temp = [[nsmutablearray alloc] initwithobjects: image, nil];      // load rest of images onto temp array     (uiimage* image in _photos)     {         [temp addobject: image];     }      _photos = nil;     _photos = [[nsmutablearray alloc] initwitharray: temp];  //    [self.photos addobject: image];     [[nsnotificationcenter defaultcenter] postnotificationname: @"photoschanged" object: self.photos];      // save cache     alassetslibrary* library = [[alassetslibrary alloc] init];     [library saveimage: image toalbum: @kalbumename withcompletionblock:^(nserror *error) {         if (error)         {             nslog(@"error saving");         }      }];  } 

i think have 2 methods optimize problem.

1. u should save image name string instead of saving uiimage object, when need display image, use pagination display image according saved image name string.

2. u should use multi-thread deal long time task, recommend u use gcd load image name string.