objective c - NSPredicate to check if attribute of object exits, if it does, get it -

i'm not sure of possible, if is, surely help.

i have nsarray of nsdictionaries.

each dictionary has keys (obviously).

dict{   title: wbccount  cat: lab } dict{  title: hbm  cat: lab  sex: male } dict{  title: hbf  cat: lab  sex: female } dict{   title: pc_count   cat: cbc   sex: female } 

i wanted filter array dictionaries have cat = 'lab' , if sex key present in dictionary object, 1 male.

in short, cannot put

predicatewithformate:%@" cat = lab , ( if sex key present, sex = male"; 

this me array of wbc, hbm.

i don't know if possible, condition within predicate, life saver if how objects sent via web api.

any other way of achiving goal if not great.

while in subject of core data, should simple: want have attribute of entity able store either nsdate or nsnumber or nsstring. there easy way out?

the trick here in nsdictionary, non-present key returns nil:

nsarray *dictionaries = @[     @{ @"title": @"t1",  @"cat":   @"lab",   @"sex":   @"male"   },     @{ @"title": @"t2",  @"cat":   @"c2"                         },     @{ @"title": @"t3",  @"cat":   @"lab",   @"sex":   @"female" },     @{ @"title": @"t4",  @"cat":   @"lab"                        } ];                      nspredicate *pred = [nspredicate predicatewithformat:@"(sex == nil or sex = 'male') , cat = 'lab'" ];  nsarray *result = [dictionaries filteredarrayusingpredicate:pred];