objective c - iOS - NSFileManager file not exist -

i hosting in-app purchase content apple. have managed download contents , right want save in device.

[[nsfilemanager defaultmanager] removeitematpath:dstpath error:nil]; [[nsfilemanager defaultmanager] copyitematpath:srcpath topath:dstpath error:nil]; 

this code above how move content downloaded desired location.

it seems work fine , when try display content works. when stop , run app again files not exist.

what missing?

my code:

- (void)processdownload:(skdownload *)download {     nsstring *path = [download.contenturl path];      path = [path stringbyappendingpathcomponent:@"contents"];      nsfilemanager *filemanager = [nsfilemanager defaultmanager];     nserror *error;     nsarray *files = [filemanager contentsofdirectoryatpath:path error:&error];      nsmutablearray *stickersdownloadedarray = [[nsmutablearray alloc] init];      (nsstring *file in files)     {         nsstring *fullpathsrc = [path stringbyappendingpathcomponent:file];          nsstring *filename = [fullpathsrc lastpathcomponent];         nsstring *fullpathdst = [[nssearchpathfordirectoriesindomains(nsdocumentdirectory, nsuserdomainmask, yes) objectatindex:0] stringbyappendingpathcomponent:[nsstring stringwithformat:@"/%@", filename]];          [filemanager removeitematpath:fullpathdst error:nil];         [filemanager moveitematpath:fullpathsrc topath:fullpathdst error:nil];          nslog(@"fullpathdst: %@", fullpathdst);         nslog(@"file: %@", file);         nslog(@"key: %@", download.transaction.payment.productidentifier);          [stickersdownloadedarray addobject:fullpathdst];     }      [[nsuserdefaults standarduserdefaults] setobject:stickersdownloadedarray                                               forkey:download.transaction.payment.productidentifier];     [[nsuserdefaults standarduserdefaults] synchronize]; } 

an example of fullpathdst is

/var/mobile/containers/data/application/e921add6-b022-4da2-8416-627db44e679a/documents/real4_12@2x.png 

an app's sandbox changes @ different times. must never store full paths files. store relative path.

in case, store path relative documents folder. when reload relative path when app starts up, recalculate full path again.