核心数据和反身关系实体

Question

好的，我建立了一个反身关系实体（在我之前发布的{SO问题] 1的帮助下。

我相信我的设置正确：

我有一个实体小组成员。我与自己建立了多对多的关系。

然后我添加一个实体并创建一个“子”实体并将其设置为关系：

GroupMember *groupMember = [NSEntityDescription insertNewObjectForEntityForName:@"GroupMember" inManagedObjectContext:context];
groupMember.name = @"Ted";

GroupMember *subGroupMember = [NSEntityDescription insertNewObjectForEntityForName:@"GroupMember" inManagedObjectContext:context];
subGroupMember.name = @"sub member bill";

[groupMember addSub_member_relObject:subGroupMember];

然后我为任何GroupMember实体发出获取请求，以查看是否已设置关系。我得到的是：

fetch objects: (
    "<GroupMember: 0x83cf280> (entity: GroupMember; id: 0x98686b0 <x-coredata://D9082F84-03D9-408D-B0DA-5C75C1B905AB/GroupMember/p1> ; data: {\n    \"member_rel\" =     (\n    );\n    name = Ted;\n    \"sub_member_rel\" =     (\n        \"0x989f390 <x-coredata://D9082F84-03D9-408D-B0DA-5C75C1B905AB/GroupMember/p2>\"\n    );\n})",
    "<GroupMember: 0x83cf4a0> (entity: GroupMember; id: 0x989f390 <x-coredata://D9082F84-03D9-408D-B0DA-5C75C1B905AB/GroupMember/p2> ; data: {\n    \"member_rel\" =     (\n        \"0x98686b0 <x-coredata://D9082F84-03D9-408D-B0DA-5C75C1B905AB/GroupMember/p1>\"\n    );\n    name = \"sub member bill\";\n    \"sub_member_rel\" =     (\n    );\n})"
)
2012-12-13 12:08:45.352 [9539:14003] name: Ted
2012-12-13 12:08:45.355 [9539:14003] set: Relationship 'sub_member_rel' on managed object (0x83cf280) <GroupMember: 0x83cf280> (entity: GroupMember; id: 0x98686b0 <x-coredata://D9082F84-03D9-408D-B0DA-5C75C1B905AB/GroupMember/p1> ; data: {
    "member_rel" =     (
    );
    name = Ted;
    "sub_member_rel" =     (
        "0x989f390 <x-coredata://D9082F84-03D9-408D-B0DA-5C75C1B905AB/GroupMember/p2>"
    );
}) with objects {(
    <GroupMember: 0x83cf4a0> (entity: GroupMember; id: 0x989f390 <x-coredata://D9082F84-03D9-408D-B0DA-5C75C1B905AB/GroupMember/p2> ; data: {
    "member_rel" =     (
        "0x98686b0 <x-coredata://D9082F84-03D9-408D-B0DA-5C75C1B905AB/GroupMember/p1>"
    );
    name = "sub member bill";
    "sub_member_rel" =     (
    );
})
)}

A）我不太明白如何阅读此输出。什么是“有对象”部分？是那个有关系的实体？ “子成员账单”是否正确设置为子成员关系？

B）当我试图回到groupMember.Sub_member_rel时，我得到一个NSSet。如何迭代这些对象以获取子成员名称（以在表格视图中显示）？

Answer 1

A）打印NSManagedObject或其关系的输出通常是冗长且有些复杂。在您的情况下，首先打印关系所属的对象。然后是“with objects”部分，它由特定关系中的对象组成。

B）在To-Many关系中，关系类型始终为NSSet。与NSArray一样，您可以像这样迭代NSSet：

for (GroupMember *subGroupMember in groupMember.sub_member_rel) {
    // Do something with managedObject
}