iPhone - 核心數據中獲取數據

Question

我設計了這樣一個數據結構：

employee 
. department 
. building 
. sector 
> number (this is a relationship to employeeData) 



employeeData 
. name 
. position 
. salary 
> number (this is a relationship to employee) 

這樣一來，將有每名僱員只有一個EmployeeData工作項。

我有所有實體的類。

現在，我該如何獲取匹配特定號碼的每個員工，然後獲取與員工相對應的employeeData？

我需要的是這個

「找到EmployeeData工作的employee.number = X」

感謝

Answer 1

事情是這樣的：

NSManagedObjectContext * context = [[NSApp delegate] managedObjectContext]; 
NSManagedObjectModel * model = [[NSApp delegate] managedObjectModel]; 
NSDictionary   * entities = [model entitiesByName]; 
NSEntityDescription * entity = [entities valueForKey:@"Employee"]; 

NSPredicate * predicate; 
predicate = [NSPredicate predicateWithFormat:@"number = %@", number]; 


NSFetchRequest * fetch = [[NSFetchRequest alloc] init]; 
[fetch setEntity: entity]; 
[fetch setPredicate: predicate]; 


NSArray * results = [context executeFetchRequest:fetch error:nil]; 
[fetch release]; 

Employee *emp = [results objectAtIndex:0]; 
EmployeeData *data = [emp data]; 

請記住，數據關係是自動如果關係是在覈心數據模型中定義的，則提取到期。這是提取和修改，以適應以下問題：http://www.cocoadevcentral.com/articles/000086.php