CoreData使用基础教程

//创建管理对象模型
    objectModel = [NSManagedObjectModel mergedModelFromBundles:nil];
    
    // 创建持久化数据存储协调器
    coordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:objectModel];
    
    // 添加数据存储
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    // 创建一个SQLite数据库作为数据存储
    NSString *documentsDir = [paths objectAtIndex:0];
    NSString *filePath = [documentsDir stringByAppendingPathComponent:@"datastore.sqlite"];
    NSURL *databaseURL = [NSURL fileURLWithPath:filePath];
    
    NSError *error = nil;
    [coordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:databaseURL options:nil error:&error];
    
    // 创建托管对象上下文
    objectCOntext= [[NSManagedObjectContext alloc] init];
    [objectContext setPersistentStoreCoordinator:coordinator];

NSString* newName = nameField.text;
    NSString* newPhOne= phoneField.text;
    NSString* newPostcode = postcodeField.text;
    
    ContactData *newCOntact= (ContactData *)[NSEntityDescription insertNewObjectForEntityForName:@"ContactData" inManagedObjectContext:objectContext];
    newContact.customerName = newName;
    newContact.phoneNumber = newPhone;
    newContact.postCode = newPostcode;
    
    NSError* error;
    
    if ([objectContext save:&error])
    {
        [self fetchExistingContactData];
        [tableofcontacts reloadData];
    }

 NSFetchRequest* fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription* entityDescription = [NSEntityDescription entityForName:@"ContactData"
                                                         inManagedObjectContext:objectContext];
    [fetchRequest setEntity:entityDescription];
    
    NSError* error;
    existingContacts = [objectContext executeFetchRequest:fetchRequest error:&error];