ios - NSSortDescriptor - Sort descriptor based on another array -


i hava core data application. , want fetch 1 kind of object, user. user have property userid.

i have array userids, [1, 4, 3, 5]. , create nssortdescriptor sorts userobjects based on order of userids in array.

is possible, , how should that?

update

i have tried following.

  1. i added transformable property user object, store user ids array.

  2. i have tried following sort descriptor:

    sortdescriptor = [[nssortdescriptor alloc] initwithkey:@"userid" ascending:yes     comparator:^nscomparisonresult(id obj1, id obj2) {     nsuinteger idx1 = [self.user.followingids indexofobject:[obj1 valueforkey:@"userid"]];     nsuinteger idx2 = [self.user.followingids indexofobject:[obj2 valueforkey:@"userid"]];     return idx1 - idx2; }];

and i'm getting following error:

serious application error.  exception caught during core data change processing.   bug within observer of nsmanagedobjectcontextobjectsdidchangenotification.   [<__nscfnumber 0xa337400> valueforundefinedkey:]: class not key value coding-compliant  key userid. userinfo {     nstargetobjectuserinfokey = 2502;     nsunknownuserinfokey = userid; } *** terminating app due uncaught exception 'nsunknownkeyexception', reason:    '[<__nscfnumber 0xa337400> valueforundefinedkey:]: class not key value coding-   compliant key userid.'

update 2

would add relationship followers between user objects. ideas how relationship should look? see attached image. correct?

enter image description here

this can not done sort descriptor, have apply custom comparator function after fetching results:

nsarray *userids = ...; // e.g. @[@1, @4, @3, @5] nsarray *results = ...; // result of fetch request nsarray *sorted = [results sortedarrayusingcomparator:^nscomparisonresult(id obj1, id obj2) {     nsuinteger idx1 = [userids indexofobject:[obj1 valueforkey:@"userid"]];     nsuinteger idx2 = [userids indexofobject:[obj2 valueforkey:@"userid"]];     return idx1 - idx2; }];

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