coredata故障信息

Question

我正在將託管記錄的內容打印到文件中。我有一個主要實體，比如MyAppEntity和幾個相關的實體（人員，地點等）。

我看到從該文件的輸出：

/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'>"; 
}) 
)} 

我有兩個問題。首先，什麼故障信息是什麼意思？第二，我如何檢索說people.name或place.name ..的值？

我可以張貼數據模型圖，但它基本上是這樣的：

MyAppEntity：屬性： 標題 日期 詳細 關係的人，地點等

PeopleEntity：屬性： 名稱 說明 訂購 關係：人

PlaceEntity：屬性： 名稱 說明 訂購 關係：地方

的關係是多對多。這是因爲一個任務可以有很多人，同一個人可以完成多項任務。

---

感謝Gerry和Marcus Zarra的另一個post。我終於得到它。如果它可以幫助別人，這是我的代碼：使用

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

故障，使數據可以僅在需要時纔會被載入。當你訪問關係時，它將被加載。請參閱Core Data Programming Guide中的Faulting and Uniquing。

一旦您訪問多對多關係，您將有一個集合。您可以枚舉集合並訪問各個管理對象上的屬性。例如（假設appObject是MyAppEntity的一個實例）：

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