ios - How can I pass the value of picker to select my Entity -

i learning core data creating expenses tracker app. have 2 entities , category , transaction. category can hold many transactions , model created correctly.

i have picker selecting category addtransactionviewcontroller. use following code save transaction when save button pressed

 _savedtransaction.type = [_pickercategories objectatindex:[_picker selectedrowincomponent:0]];  _savedtransaction.timestamp = [nsdate date];  _savedtransaction.amount = transactionamount.text  _savedtransaction.category = _transactioncategory; 

i sure doing stupid save because _savedtransaction.categoryis returning null when log it. other parameters log correctly, transaction saved... how can store transactioncategory value set picker?

you have pass value of picker view category

_savedtransaction.category = [_pickercategories objectatindex:[_picker selectedrowincomponent:0]];