coredata故障消息

Question

我正在将托管记录的内容打印到文件中。 我有一个主要实体，例如MyAppEntity，还有几个相关的实体（人，地方等）。

我正在从文件中看到以下输出：

/Users/david/Library/Application Support/iPhone Simulator/5.1/Applications/C9ACA218-F2D6-4623-8CAF-5FE763D10FC8/Documents/
 MyApp-0001 12.01.25 
 Summary goes here... 
 Nothing here yet. 
 Relationship 'people' on managed object (0x79eaf7f0) <NSManagedObject: 0x79eaf7f0> (entity: MyAppEntity; id: 0x79eae950 <x-coredata:/B86C9CA8-EDE4-452C-BA56-FEF50B4F0FF9/MyAppEntity/p1> ; data: {
    audioName = 00010125121910;
    audioNo = 0;
    date = nil;
    MyApp = "MyApp-0001 12.01.25";
    interpret = "Nothing here yet.";
    keyword =     (
    );
    order = 0;
    people =     (
        "0x79ee42f0 <x-coredata:/B86C9CA8-EDE4-452C-BA56-FEF50B4F0FF9/PeopleEntity/p1>",
        "0x79ee4300 <x-coredata:/B86C9CA8-EDE4-452C-BA56-FEF50B4F0FF9/PeopleEntity/p2>"
    );
    place =     (
        "0x79ee6970 <x-coredata:/B86C9CA8-EDE4-452C-BA56-FEF50B4F0FF9/PlaceEntity/p2>",
        "0x79ee6960 <x-coredata:/B86C9CA8-EDE4-452C-BA56-FEF50B4F0FF9/PlaceEntity/p1>"
    );
    recurring = 0;
    summary = "Summary goes here...";
    symbol =     (
    );
    type =     (
    );
}) with objects {(
    <NSManagedObject: 0x79ee47e0> (entity: PeopleEntity; id: 0x79ee42f0 <x-coredata:/B86C9CA8-EDE4-452C-BA56-FEF50B4F0FF9/PeopleEntity/p1> ; data: {
    definition = nil;
    name = me;
    order = 0;
    people = "<relationship fault: 0x79ef5ce0 'people'>";
}),
    <NSManagedObject: 0x79ee4a70> (entity: PeopleEntity; id: 0x79ee4300 <x-coredata:/B86C9CA8-EDE4-452C-BA56-FEF50B4F0FF9/PeopleEntity/p2> ; data: {
    definition = nil;
    name = you;
    order = 1;
    people = "<relationship fault: 0x79e60840 'people'>";
})
)} 

我有两个问题...首先，故障消息是什么意思？ 第二，如何检索诸如people.name或place.name ..的值？

我可以发布数据模型图，但是它基本上看起来像这样：

MyAppEntity：属性：标题日期详细信息与人，地点等的关系。

PeopleEntity：属性：名称说明订单关系：people

PlaceEntity：属性：名称说明订单关系：place

关系是多对多的。 这是因为一个任务可以有很多人，而同一个人可以从事多个任务。

---

感谢Gerry和Marcus Zarra在另一篇文章中 。 我终于明白了。如果可以帮助别人，这是我的代码：

NSManagedObjectContext *context = [self managedObjectContext];  
    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init];
    NSEntityDescription *mainEntity = [NSEntityDescription entityForName:@"MainEntity" inManagedObjectContext:context];

    [fetchRequest setEntity:mains]; 
    NSError *error = nil;   
    NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&error];


    NSLog(@"Record Count is: %i", [fetchedObjects count]);

    // THIS ACTUALLY WORKS.....

     for (MainEntity *mains in fetchedObjects) {
     NSLog(@"Main: %@", mains.name);
         NSSet *peopleSet = [mains valueForKey:@"people"];   
         for (id person in peopleSet) {
             NSLog(@"name = %@", [person valueForKey:@"name"]);
         }
         NSSet *keywordSet = [mains valueForKey:@"keyword"];     
         for (id keyWord in keywordSet) {
             NSLog(@"Keyword = %@", [keyWord valueForKey:@"word"]);
         }
         NSSet *placeSet = [mains valueForKey:@"place"];     
         for (id places in placeSet) {
             NSLog(@"Place = %@", [places valueForKey:@"name"]);
         }
         NSSet *symbolSet = [mains valueForKey:@"symbol"];   
         for (id symbols in symbolSet) {
             NSLog(@"Symbol = %@", [symbols valueForKey:@"symbolName"]);
         }
         NSSet *typeSet = [mains valueForKey:@"type"];   
         for (id types in typeSet) {
             NSLog(@"Type = %@", [types valueForKey:@"typeName"]);
         }
     }

    if (!fetchedObjects || error) {
        NSLog(@"[ERROR] COREDATA: Fetch request raised an error - '%@'", [error description]);
        return;
    }

Answer 1

使用故障，以便仅在需要时才可以加载数据。 当您访问该关系时，它将被加载。 请参阅《 核心数据编程指南》中的“ 故障和唯一性 ” 。

访问多对多关系后，您将获得一个集合。 您可以枚举集合并访问各个受管对象上的属性。 例如（假设appObject是MyAppEntity的实例）：

for (id person in [appObject valueForKey:@"people"]) {
    NSLog(@"name = %@", [person valueForKey:@"name"]);
}