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我的數據模型有如下關係:核心數據 - 保存關係的技巧?
[Account] -|------o< [Transaction]
作爲實現:
// in Account.h
@property (nonatomic, retain) NSSet *transactions;
// in Transaction.h
@property (nonatomic, retain) Account *account;
現在,我已經成功地創建了一個帳戶並將其插入到核心數據。我的問題是,如何向帳戶添加起始餘額?這顯然只是賬戶上的一項交易,但在數據模型中,以下兩種方式足以實現連接(即連接newAccount.transactions
以及newTransaction.account
)?
// we need to insert a new account
Account *newAccount = [NSEntityDescription insertNewObjectForEntityForName:[Account entityName] inManagedObjectContext:self.managedObjectContext];
// . . . configure newAccount
NSNumber *startingBalance = @([self.startingBalanceTextField.text floatValue]);
NSError *error;
// save the new account
[self.managedObjectContext save:&error];
if(!error)
{
Transaction *newTransaction = [NSEntityDescription insertNewObjectForEntityForName:[Transaction entityName] inManagedObjectContext:self.managedObjectContext];
// . . . configure newTransaction
// is this sufficient & proper? Will this add newTransaction to newAccount.transactions as well?
newTransaction.account = newAccount;
// save the starting balance
[self.managedObjectContext save:&error];
}