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，比如MyAppEntity和几个相关实体（人物，地方等）。

我在文件中看到了这个输出：

/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，故障信息是什么意思？第二，如何检索say people.name或place.name ..？

的值

我可以发布数据模型图，但它基本上是这样的：

MyAppEntity：属性：标题日期细节关系人，地点等

PeopleEntity：属性：名称描述订购关系：人

PlaceEntity：属性：名称描述订购关系：地点

关系是多对多的。这是因为一个任务可以有很多人，同一个人可以处理多个任务。

感谢Gerry和另一位post的Marcus Zarra。我终于明白了..如果它对别人有帮助，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

使用了故障，因此只有在需要时才能加载数据。当您访问该关系时，它将被加载。请参阅Faulting and Uniquing中的Core Data Programming Guide。

一旦您访问了多对多关系，您将拥有一套。您可以枚举集合并访问各个受管对象的属性。例如（假设appObject是MyAppEntity的一个实例）：

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

coredata故障消息

1 个答案: