ios - Show only part of coreData array -

i've tableview should display objects of coredata-entity if 1 of entity-attribute equal string.

there's entity called buy , 1 of it's attribute string called position

and in code tableviewcontroller is:

@property (strong) nsmutablearray *buy;  - (nsmanagedobjectcontext *)managedobjectcontext {     nsmanagedobjectcontext *context = nil;     id delegate = [[uiapplication sharedapplication] delegate];     if ([delegate performselector:@selector(managedobjectcontext)]) {         context = [delegate managedobjectcontext];     }     return context; }      - (void)viewdidappear:(bool)animated     {         [super viewdidappear:animated];             nsmanagedobjectcontext *managedobjectcontext = [self managedobjectcontext];         nsfetchrequest *fetchrequest = [[nsfetchrequest alloc] initwithentityname:@"buy"];             self.buy= [[managedobjectcontext executefetchrequest:fetchrequest error:nil] mutablecopy];            [self.tableview reloaddata];     } 

and try display objects of buy contain position string equal "a". don't how write if-condition.

thanks answers in advance.

do following :-

nsstring *str="a"; nspredicate *predicate=[nspredicate predicatewithformat:@"position == %@",str];  

so, viewdidappear function becomes :-

- (void)viewdidappear:(bool)animated     {         [super viewdidappear:animated];             nsmanagedobjectcontext *managedobjectcontext = [self managedobjectcontext];         nsstring *str="a";         nspredicate *predicate=[nspredicate predicatewithformat:@"position == %@",str];          nsfetchrequest *fetchrequest = [[nsfetchrequest alloc] initwithentityname:@"buy"];         [fetchrequest setpredicate : predicate ];             self.buy= [[managedobjectcontext executefetchrequest:fetchrequest error:nil] mutablecopy];            [self.tableview reloaddata];     }