Ios 如何基于双向关系从核心数据中提取数据？

在我的示例应用程序中，我有两个实体，分别称为Accounts和Customer

对于这些实体，我创建了两个NSManagedObject子类

imgur.com/zmt1N.png

现在确切地说，我不知道它是否正确，我必须保存到这些核心数据实体并检索详细信息，如“帐户表中有三个以上帐户的客户””

期待一点详细的解释。提前感谢

使用NSPredicate

-(void)fetchCoreDAta
{


    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];

    NSFetchRequest *fetchRequest1 = [[NSFetchRequest alloc] init];

    NSEntityDescription *entity = [NSEntityDescription entityForName:@"Customer" inManagedObjectContext:self.managedObjectContext];

    NSEntityDescription *entityAccounts = [NSEntityDescription entityForName:@"Accounts" inManagedObjectContext:self.managedObjectContext];

    [fetchRequest setEntity:entity];

    [fetchRequest1 setEntity:entityAccounts];

  //  [fetchRequest1 setEntity:entity];


#pragma mark - using predicates for fetching customer name who having three accounts

    NSPredicate *predicate =[NSPredicate predicateWithFormat:@"cust_relation.@count == 4"];
  //  NSPredicate *predicate1 =   [NSPredicate predicateWithFormat:@"ANY account_relation.name LIKE[c] 'Vijeesh'"];

       NSPredicate *predicate1 =   [NSPredicate predicateWithFormat:@"ANY account_relation.name like 'Vijeesh'"];


    NSString *value1 =@"Ansal";
    NSString *value2 =@"Vijeesh";



  //  NSPredicate *predicate2 = [NSPredicate predicateWithFormat:@"(name == %@) AND (SUBQUERY(subs, $x, $x.numbervalue == %@ or $x.numbervalue == %@).@count > 0)", @"Yeswant", value1, value2] ;

   [fetchRequest setPredicate:predicate];

   [fetchRequest1 setPredicate:predicate1];



    NSError *error = nil;


    NSArray *result = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error];


    NSArray *resultAccounts = [self.managedObjectContext executeFetchRequest:fetchRequest1 error:&error];

    if (error)
    {
        NSLog(@"Unable to execute fetch request.");
        NSLog(@"%@, %@", error, error.localizedDescription);

    }
    else
    {
        NSLog(@"%@", result);
        NSLog(@"accounts:%@",resultAccounts);

        NSMutableArray * userNAmeArray = [result valueForKey:@"name"];

        NSMutableArray * accountsnumberArray = [resultAccounts valueForKey:@"accountNumber"];

        NSLog(@"names:%@",userNAmeArray);
        NSLog(@"acnums:%@",accountsnumberArray);


    }
     }

一个简单的示例，使用不区分大小写的字符串“搜索”名称：

NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"customer"];

request.predicate = [NSPredicate predicateWithFormat:@"name LIKE[c] %@", @"Amazon"];

NSArray *matches = [self.managedObjectContext executeFetchRequest:request error:nil];

根据上面链接的NSPredicate类别参考：

您可以为关系创建谓词，例如：

group.name，如“work*”

所有年龄>12岁的儿童

任何年龄超过12岁的儿童

---

这就是我期望做的。谢谢你的帮助

-(void)savingDummyDatas
{

    NSManagedObjectContext *context = [self managedObjectContext];
    NSEntityDescription *entityDesc = [NSEntityDescription entityForName:@"Customer" inManagedObjectContext:context];
        NSFetchRequest *request = [[NSFetchRequest alloc] init];
    [request setEntity:entityDesc];
    NSError *error;
    NSArray *objects = [context executeFetchRequest:request error:&error];

//execution starting time
    NSDate *methodStart = [NSDate date];
// 
    if ([objects count] == 0)
    {

#pragma mark - Entity Insertion With Relation

//for (int i=1; i<=100000; i++) {
        //1

        Customer *custObj1 = [NSEntityDescription insertNewObjectForEntityForName:@"Customer" inManagedObjectContext:context];
        custObj1.name = @"Yeswant";
        // add accoutns for customer

        Accounts *acObj1 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj1.accountNumber = @"001";

        [custObj1 addCust_relationObject:acObj1];

        Accounts *acObj2 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj2.accountNumber = @"002";
        [custObj1 addCust_relationObject:acObj2];

        Accounts *acObj3 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj3.accountNumber =@"003";
        [custObj1 addCust_relationObject:acObj3];

        Accounts *acObj4 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj4.accountNumber =@"004";
        [custObj1 addCust_relationObject:acObj4];

    //2

        Customer *custObj2 = [NSEntityDescription insertNewObjectForEntityForName:@"Customer" inManagedObjectContext:context];
        custObj2.name= @"Bharath";
        // add accoutns for customer

        Accounts *acObj01 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj01.accountNumber = @"010";
        [custObj2 addCust_relationObject:acObj01];

        Accounts *acObj02 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj02.accountNumber = @"011";
        [custObj2 addCust_relationObject:acObj02];

        Accounts *acObj03 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj03.accountNumber =@"101";
        [custObj2 addCust_relationObject:acObj03];

//3
        Customer *custObj3 = [NSEntityDescription insertNewObjectForEntityForName:@"Customer" inManagedObjectContext:context];
        custObj3.name = @"Ansal";
        // add accoutns for customer

        Accounts *acObj001 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj001.accountNumber = @"001";

        [custObj3 addCust_relationObject:acObj001];

        Accounts *acObj002 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj002.accountNumber = @"002";
        [custObj3 addCust_relationObject:acObj002];

        Accounts *acObj003 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj003.accountNumber =@"003";
        [custObj3 addCust_relationObject:acObj003];

        Accounts *acObj004 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj004.accountNumber =@"004";
        [custObj3 addCust_relationObject:acObj004];


    //4

        Customer *custObj4 = [NSEntityDescription insertNewObjectForEntityForName:@"Customer" inManagedObjectContext:context];
        custObj4.name = @"Vijeesh";
        // add accoutrns for customer

        Accounts *acObj0001 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj0001.accountNumber = @"010";
        [custObj4 addCust_relationObject:acObj0001];

        Accounts *acObj0002 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj0002.accountNumber = @"011";
        [custObj4 addCust_relationObject:acObj0002];

        Accounts *acObj0003 = [NSEntityDescription insertNewObjectForEntityForName:@"Accounts" inManagedObjectContext:context];
        acObj0003.accountNumber =@"101";
        [custObj4 addCust_relationObject:acObj0003];
[context save:nil];



   }

---

是的，我们可以用它。但是我将如何与这两个表关联（我在创建表时创建了关系，但我不知道这些实体是如何相互关联的）。比如一个人在下一个账户实体中拥有两个以上的账户。插入值时是否也要执行任何特定操作？我必须从第一个实体获取客户，该客户拥有三个或更多帐户，然后从下一个实体获取帐户