iphone - NSDictionary Error Handling -

i creating application don't know how handle error when there no value given entry in nsdictionary. here code have currently:

   nsdictionary *entry = [self entries][indexpath.row];     nsdictionary *text = [self entries][indexpath.row];     nsstring *user = entry[@"user"][@"full_name"];     nsstring *caption = text[@"caption"][@"text"];      if (caption != nil && entry != [nsnull null] && text != nil && caption != [nsnull null]) {         rnblurmodalview *modal = [[rnblurmodalview alloc] initwithviewcontroller:self title:user message:caption];         [modal show];     } 

here error response receive when tap on cell without caption:

2013-08-08 02:36:57.871 floadt[5566:c07] -[nsnull objectforkeyedsubscript:]: unrecognized selector sent instance 0x310b678 2013-08-08 02:36:57.872 floadt[5566:c07] *** terminating app due uncaught exception 'nsinvalidargumentexception', reason: '-[nsnull objectforkeyedsubscript:]: unrecognized selector sent instance 0x310b678' *** first throw call stack: (0x2fda012 0x260be7e 0x30654bd 0x2fc9bbc 0x2fc994e 0x5606b 0x1c7a42f 0x1c8c182 0x1c8c394 0x261f705 0x188693c 0x18869ac 0x261f705 0x188693c 0x18869ac 0x1a401d3 0x2fa2afe 0x2fa2a3d 0x2f807c2 0x2f7ff44 0x2f7fe1b 0x2bb77e3 0x2bb7668 0x1778ffc 0x2d2d 0x2c55) libc++abi.dylib: terminate called throwing exception 

not clear why entry , text same thing. typo causing issues:

nsdictionary *entry = [self entries][indexpath.row]; nsdictionary *text = [self entries][indexpath.row]; 

then, should use isequal equality checks (even if prevent getting bad habits) , check obtained values (you don't check user):

if (![user isequal:[nsnull null]] && ![caption isequal:[nsnull null]]) { 

your current checks redundant - need check things before use them, not afterwards. checking entry , text must done earlier. check user , caption.