Core data 永久的NSManagedObjectd不是那么永久吗？
我在处理CoreData中的对象ID时遇到问题。为了方便起见，我使用MagicalRecord，它有3个上下文：一个专用队列工作上下文、一个UI的主队列上下文和工作上下文的父上下文，以及一个作为主上下文父上下文的专用队列保存上下文 我的目标是在工作上下文中创建一个对象，保存到持久性存储，将其objectID URL保存到NSUserDefaults，然后能够稍后使用objectID提取该MO。然而，我发现在保存对象的永久ID之后，它正在发生变化 在下面的控制台输出中，您可以看到，在我请求永久ID后，我返回的值是“F474F6EE-A225-456B-92EF-AB1407336F15/CDBaseCount/p1”，但稍后当我列出CD中的所有对象时，唯一的对象ID是“F474F6EE-A225-456B-92EF-AB1407336F15/CDBaseCount/p2”。p1对p2，发生了什么 代码： 控制台输出：Core data 永久的NSManagedObjectd不是那么永久吗？,core-data,nsmanagedobject,magicalrecord,Core Data,Nsmanagedobject,Magicalrecord,我在处理CoreData中的对象ID时遇到问题。为了方便起见，我使用MagicalRecord，它有3个上下文：一个专用队列工作上下文、一个UI的主队列上下文和工作上下文的父上下文，以及一个作为主上下文父上下文的专用队列保存上下文 我的目标是在工作上下文中创建一个对象，保存到持久性存储，将其objectID URL保存到NSUserDefaults，然后能够稍后使用objectID提取该MO。然而，我发现在保存对象的永久ID之后，它正在发生变化 在下面的控制台输出中，您可以看到，在我请求永久ID
> +[NSManagedObjectContext(MagicalRecord) MR_contextWithStoreCoordinator:](0xa7c9b0) -> Created <NSManagedObjectContext: 0x83522a0>: Context *** MAIN THREAD ***
> count: 0
> all accounts = (
> )
> -[NSManagedObjectContext(MagicalSaves) MR_saveWithErrorCallback:](0x8353de0) -> Saving <NSManagedObjectContext: 0x8353de0>: Context *** MAIN THREAD ***
> -[NSManagedObjectContext(MagicalSaves) MR_saveWithErrorCallback:](0x8195450) -> Saving <NSManagedObjectContext: 0x8195450>: *** DEFAULT *** Context *** MAIN THREAD ***
> -[NSManagedObjectContext(MagicalSaves) MR_saveWithErrorCallback:](0x83522a0) -> Saving <NSManagedObjectContext: 0x83522a0>: *** BACKGROUND SAVE *** Context *** MAIN THREAD ***
> temp a.objectID = 0x8187ee0 <x-coredata:///CDBaseAccount/tF392AC6A-3539-4F39-AC53-35F9E5B3C9322>
> perm a.objectID = 0x8355800 <x-coredata://F474F6EE-A225-456B-92EF-AB1407336F15/CDBaseAccount/p2>
> count: 1
> all accounts = (
"<CDBaseAccount: 0x844ca60> (entity: CDBaseAccount; id: 0x844a4c0 <x-coredata://F474F6EE-A225-456B-92EF-AB1407336F15/CDBaseAccount/p1> ; data: <fault>)"
)
> existing object error: Error Domain=NSCocoaErrorDomain Code=133000 "The operation couldn’t be completed. (Cocoa error 133000.)" UserInfo=0x864d8c0 {NSAffectedObjectsErrorKey=(
"<CDBaseAccount: 0x864b8c0> (entity: CDBaseAccount; id: 0x86405c0 <x-coredata://F474F6EE-A225-456B-92EF-AB1407336F15/CDBaseAccount/p2> ; data: <fault>)"
)}
+[NSManagedObjectContext（MagicalRecord）MR_contextWithStoreCoordinator:（0xa7c9b0）->已创建：上下文***主线程***
>计数：0
>所有帐户=(
> )
>-[NSManagedObjectContext（MagicalSaves）MR_saveWithErrorCallback:]（0x8353de0）->保存：上下文***主线程***
>-[NSManagedObjectContext（MagicalSaves）MR_saveWithErrorCallback:（0x8195450）->保存：**默认***上下文***主线程***
>-[NSManagedObjectContext（MagicalSaves）MR_saveWithErrorCallback:（0x83522a0）->保存：**后台保存***上下文***主线程***
>临时a.objectID=0x8187ee0
>perm a.objectID=0x8355800
>计数：1
>所有帐户=(
“（实体：CDBaseCount；id:0x844a4c0；数据：）”
)
>现有对象错误：错误域=NSCOCAERRORDOMAIN代码=133000“该操作无法完成。（Cocoa错误133000。）”用户信息=0x864d8c0{NSACTIVEDOBJECTSERRORKEY=(
“（实体：CDBaseCount；id:0x86405c0；数据：）”
)}
简而言之，不要这样做：）
-objectID
在应用程序启动之间不可靠。在以下条件下，保证其唯一性和可靠性：
在应用程序的单个生命周期内
以其原始对象形式（不是URL或NSString形式）
将-objectID
视为永久唯一标识符存储在持久性存储区之外会经常失败。核心数据在对象的生命周期内多次更改-objectID
的基本细节
如果你需要一个外部可靠的唯一，那么你需要自己创建一个。我通常建议将[[NSProcessInfo processInfo]globallyUniqueString]
添加到任何需要外部引用的唯一实体<代码>-awakeFromInsert
是一个很好的地方。这可能是因为您使用的是嵌套上下文
#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
static NSArray *fetchAllPersons(NSManagedObjectContext *moc);
static NSManagedObjectModel *managedObjectModel();
static NSManagedObjectContext *createManagedObjectContext();
static NSURL *desktopDirectoryURL(void);
static void testObjectID(void);
int main(int argc, const char * argv[])
{
@autoreleasepool {
dispatch_async(dispatch_get_global_queue(0, 0), ^{
testObjectID();
});
}
dispatch_main();
return 0;
}
static void testObjectID(void)
{
NSManagedObjectContext *c = createManagedObjectContext();
[c performBlock:^{
NSArray *all = fetchAllPersons(c);
NSLog(@"count: %lu", all.count);
NSLog(@"all accounts = %@", all);
NSManagedObject *a = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:c];
[a setValue:@"foo" forKey:@"name"];
NSLog(@"temp a.objectID = %@", a.objectID);
NSError *error = nil;
NSCAssert([c obtainPermanentIDsForObjects:@[a] error:&error], @"perm id error: %@", error);
NSLog(@"perm a.objectID = %@", a.objectID);
NSCAssert([c save:&error], @"Save failed: %@", error);
NSURL *u = a.objectID.URIRepresentation;
dispatch_async(dispatch_get_global_queue(0, 0), ^{
NSManagedObjectContext *d = createManagedObjectContext();
NSArray *all = fetchAllPersons(c);
NSLog(@"count: %lu", all.count);
NSLog(@"all accounts = %@", all);
NSManagedObjectID *i = [d.persistentStoreCoordinator managedObjectIDForURIRepresentation:u];
NSError *objWithIdError = nil;
NSManagedObject *o = [d existingObjectWithID:i error:&objWithIdError];
NSCAssert(o != nil, @"existing object error: %@", objWithIdError);
NSLog(@"o = %@", o);
NSLog(@"o.objectID = %@", o.objectID);
});
}];
}
static NSArray *fetchAllPersons(NSManagedObjectContext *moc)
{
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
NSError *error = nil;
NSArray *result = [moc executeFetchRequest:request error:&error];
NSCAssert(result != nil, @"Fetch failed: %@", error);
return result;
}
static NSManagedObjectModel *managedObjectModel()
{
static NSManagedObjectModel *mom = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
NSEntityDescription *personEntity = [[NSEntityDescription alloc] init];
[personEntity setName:@"Person"];
NSAttributeDescription *nameAttribute = [[NSAttributeDescription alloc] init];
[nameAttribute setName:@"name"];
[nameAttribute setAttributeType:NSStringAttributeType];
[personEntity setProperties:@[nameAttribute]];
mom = [[NSManagedObjectModel alloc] init];
[mom setEntities:@[personEntity]];
});
return mom;
}
static NSManagedObjectContext *createManagedObjectContext()
{
static NSPersistentStoreCoordinator *coordinator;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
coordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: managedObjectModel()];
NSString *STORE_TYPE = NSSQLiteStoreType;
NSString *STORE_FILENAME = @"foobar.db";
NSError *error;
NSURL *url = [desktopDirectoryURL() URLByAppendingPathComponent:STORE_FILENAME];
NSPersistentStore *newStore = [coordinator addPersistentStoreWithType:STORE_TYPE
configuration:nil URL:url options:nil
error:&error];
if (newStore == nil) {
NSLog(@"Store Configuration Failure\n%@",
([error localizedDescription] != nil) ?
[error localizedDescription] : @"Unknown Error");
}
});
NSManagedObjectContext *moc = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
[moc setPersistentStoreCoordinator:coordinator];
return moc;
}
static NSURL *desktopDirectoryURL(void)
{
static NSURL *URL;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
NSFileManager *fileManager = [[NSFileManager alloc] init];
NSError *error;
URL = [fileManager URLForDirectory:NSDesktopDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:YES error:&error];
NSCAssert(URL != nil, @"Could not access Desktop directory: %@", [error localizedDescription]);
});
return URL;
}
#导入
#进口
静态NSArray*fetchAllPersons（NSManagedObjectContext*moc）；
静态NSManagedObjectModel*managedObjectModel（）；
静态NSManagedObjectContext*createManagedObjectContext（）；
静态NSURL*desktopDirectoryURL（无效）；
静态void testObjectID（void）；
int main（int argc，const char*argv[]
{
@自动释放池{
调度异步（调度获取全局队列（0,0）^{
testObjectID（）；
});
}
调度_main（）；
返回0；
}
静态void testObjectID（void）
{
NSManagedObjectContext*c=createManagedObjectContext（）；
[c性能块：^{
NSArray*all=fetchAllPersons（c）；
NSLog（@“计数：%lu”，全部.count）；
NSLog（@“所有帐户=%@”，全部）；
NSManagedObject*a=[NSEntityDescription insertNewObjectForEntityForName:@“Person”在ManagedObject上下文中：c]；
[a setValue:@“foo”forKey:@“name”]；
NSLog（@“temp a.objectID=%@”，a.objectID）；
n错误*错误=nil；
NSCAssert（[c获取永久对象：@[a]错误：&错误]，@“perm id error:%@”，错误）；
NSLog（@“perm a.objectID=%@”，a.objectID）；
NSCAssert（[c保存：&错误]，@“保存失败：%@”，错误）；
NSURL*u=a.objectID.Uri表示法；
调度异步（调度获取全局队列（0,0）^{
NSManagedObjectContext*d=createManagedObjectContext（）；
NSArray*all=fetchAllPersons（c）；
NSLog（@“计数：%lu”，全部.count）；
NSLog（@“所有帐户=%@”，全部）；
NSManagedObjectID*i=[d.persistentStoreCoordinator ManagedObjectdForUriRepresentation:u]；
n错误*objWithIdError=nil；
NSManagedObject*o=[d个ID为：i的现有对象错误：&objWithIdError]；
NSCAssert（o！=nil，@“现有对象错误：%@”，objWithIdError）；
NSLog（@“o=%@”，o）；
NSLog（@“o.objectID=%@”，o.objectID）；
});
}];
}
静态NSArray*fetchAllPersons（NSManagedObjectContext*moc）
{
NSFetchRequest*request=[NSFetchRequest fetchRequestWithEntityName:@“Person”]；
n错误*错误=nil；
NSArray*结果=[moc executeFetchRequest:请求错误：&错误]；
NSCAssert（结果！=nil，@“获取失败：%@”，错误）；
返回结果；
}
静态NSManagedObjectModel*managedObjectModel（）
{
静态NSManagedObjectModel*mom=nil；
静态调度一次；
一次发送（一次发送）^{
NSEntityDescription*personEntity=[[NSEntityDescription alloc]init]；
[personEntity集合名：@“Person”]；
NSAttributedDescription*nameAttribute=[[NSAttributedDescription alloc]init]；
[名称属性集合名称：@“名称”]；
[nameAttribute setAttributeType:NSStringAttributeType]；
[personEntity setProperties:@[nameAttribute]；
mom=[[NSManagedObjectModel alloc]init]；
[mom setEntities:@[personEntity]]；
});
返回妈妈；
}
静态NSManagedObjectContext*createManagedObjectContext（）
{
静态NSPersistentStoreCoordinator*协调器；
静态调度一次；
调度
#import <Foundation/Foundation.h>
#import <CoreData/CoreData.h>
static NSArray *fetchAllPersons(NSManagedObjectContext *moc);
static NSManagedObjectModel *managedObjectModel();
static NSManagedObjectContext *createManagedObjectContext();
static NSURL *desktopDirectoryURL(void);
static void testObjectID(void);
int main(int argc, const char * argv[])
{
@autoreleasepool {
dispatch_async(dispatch_get_global_queue(0, 0), ^{
testObjectID();
});
}
dispatch_main();
return 0;
}
static void testObjectID(void)
{
NSManagedObjectContext *c = createManagedObjectContext();
[c performBlock:^{
NSArray *all = fetchAllPersons(c);
NSLog(@"count: %lu", all.count);
NSLog(@"all accounts = %@", all);
NSManagedObject *a = [NSEntityDescription insertNewObjectForEntityForName:@"Person" inManagedObjectContext:c];
[a setValue:@"foo" forKey:@"name"];
NSLog(@"temp a.objectID = %@", a.objectID);
NSError *error = nil;
NSCAssert([c obtainPermanentIDsForObjects:@[a] error:&error], @"perm id error: %@", error);
NSLog(@"perm a.objectID = %@", a.objectID);
NSCAssert([c save:&error], @"Save failed: %@", error);
NSURL *u = a.objectID.URIRepresentation;
dispatch_async(dispatch_get_global_queue(0, 0), ^{
NSManagedObjectContext *d = createManagedObjectContext();
NSArray *all = fetchAllPersons(c);
NSLog(@"count: %lu", all.count);
NSLog(@"all accounts = %@", all);
NSManagedObjectID *i = [d.persistentStoreCoordinator managedObjectIDForURIRepresentation:u];
NSError *objWithIdError = nil;
NSManagedObject *o = [d existingObjectWithID:i error:&objWithIdError];
NSCAssert(o != nil, @"existing object error: %@", objWithIdError);
NSLog(@"o = %@", o);
NSLog(@"o.objectID = %@", o.objectID);
});
}];
}
static NSArray *fetchAllPersons(NSManagedObjectContext *moc)
{
NSFetchRequest *request = [NSFetchRequest fetchRequestWithEntityName:@"Person"];
NSError *error = nil;
NSArray *result = [moc executeFetchRequest:request error:&error];
NSCAssert(result != nil, @"Fetch failed: %@", error);
return result;
}
static NSManagedObjectModel *managedObjectModel()
{
static NSManagedObjectModel *mom = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
NSEntityDescription *personEntity = [[NSEntityDescription alloc] init];
[personEntity setName:@"Person"];
NSAttributeDescription *nameAttribute = [[NSAttributeDescription alloc] init];
[nameAttribute setName:@"name"];
[nameAttribute setAttributeType:NSStringAttributeType];
[personEntity setProperties:@[nameAttribute]];
mom = [[NSManagedObjectModel alloc] init];
[mom setEntities:@[personEntity]];
});
return mom;
}
static NSManagedObjectContext *createManagedObjectContext()
{
static NSPersistentStoreCoordinator *coordinator;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
coordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel: managedObjectModel()];
NSString *STORE_TYPE = NSSQLiteStoreType;
NSString *STORE_FILENAME = @"foobar.db";
NSError *error;
NSURL *url = [desktopDirectoryURL() URLByAppendingPathComponent:STORE_FILENAME];
NSPersistentStore *newStore = [coordinator addPersistentStoreWithType:STORE_TYPE
configuration:nil URL:url options:nil
error:&error];
if (newStore == nil) {
NSLog(@"Store Configuration Failure\n%@",
([error localizedDescription] != nil) ?
[error localizedDescription] : @"Unknown Error");
}
});
NSManagedObjectContext *moc = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType];
[moc setPersistentStoreCoordinator:coordinator];
return moc;
}
static NSURL *desktopDirectoryURL(void)
{
static NSURL *URL;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
NSFileManager *fileManager = [[NSFileManager alloc] init];
NSError *error;
URL = [fileManager URLForDirectory:NSDesktopDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:YES error:&error];
NSCAssert(URL != nil, @"Could not access Desktop directory: %@", [error localizedDescription]);
});
return URL;
}
count: 0
all accounts = (
)
temp a.objectID = 0x10180e640 <x-coredata:///Person/tB1D48677-0152-4DA9-8573-7C7532863B4E2>
perm a.objectID = 0x101901bb0 <x-coredata://275C90E5-2598-4DFA-BF4C-E60A336E8BE4/Person/p1>
count: 1
all accounts = (
"<NSManagedObject: 0x10180e5b0> (entity: Person; id: 0x101901bb0 <x-coredata://275C90E5-2598-4DFA-BF4C-E60A336E8BE4/Person/p1> ; data: {\n name = foo;\n})"
)
o = <NSManagedObject: 0x100416530> (entity: Person; id: 0x100415b60 <x-coredata://275C90E5-2598-4DFA-BF4C-E60A336E8BE4/Person/p1> ; data: {
name = foo;
})
o.objectID = 0x100415b60 <x-coredata://275C90E5-2598-4DFA-BF4C-E60A336E8BE4/Person/p1>