core data model的讀寫

1. 新增一行資料至table
ex:
假設model的類別為Person

Person *person = [NSEntityDescription    

   insertNewObjectForEntityForName:@"Person" 

   inManagedObjectContext:self.managedObjectContext];

if(person != nil)

{

        person.age = [NSNumber numberWithInt:1];

        person.name = @"peter";

        

        NSError *saveError = nil;

        if([self.managedObjectContext save:&saveError] == YES)

        {

            NSLog(@"save new rocord successfully");

        }

}

說明:

利用insertNewObjectForEntityForName:inManagedObjectContext: method新增資料。不過這只是暫時的，若要真的將資料存入database，需呼叫NSManagedObjectContext物件的save: method

2. 從table讀取資料

ex:

假設model的類別為Person

NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] 

    init];

NSEntityDescription *entity = [NSEntityDescription  

    entityForName:@"Person" 

    inManagedObjectContext:self.managedObjectContext];

[fetchRequest setEntity:entity];

NSError *error = nil;

NSArray *personArray = [self.managedObjectContext 

    executeFetchRequest:fetchRequest error:&error];

for(Person *person in personArray)

{

   NSLog(@"name %@", person.name);

}

說明:

(1)利用NSFetchRequest物件設定尋找的條件

(2)運用NSManagedObjectContext物件的executeFetchRequest:error: 

   method尋找符合條件的資料。