我是 Core Data 的新手,因此我不确定我是否犯了错误。我从 REST API 下载了一些数据,它成功地将JSON
响应保存到磁盘。我正在尝试处理数据并使用 Core Data 持久保存它。
NSLog(@"inserted objects: %@", [managedObjectContext insertedObjects]);
[managedObjectContext performBlockAndWait:^{
NSError *error = nil;
if (![managedObjectContext save:&error]) {
NSLog(@"Unable to save context for class %@", className);
} else {
NSLog(@"saved all records!");
}
}];
我已成功处理JSON
并将其添加到NSManagedObjectContext
. 在第一行中,它表明我已成功尝试插入 2 个对象。
inserted objects: {(
<User: 0xa259af0> (entity: User; id: 0xa259b70 <x-coredata:///User/t44BB97D0-C4B4-4BA6-BD25-13CEFDAE665F3> ; data: {
email = "vishnu@vishnuprem.com";
experience = "2013-07-20";
"first_name" = Vishnu;
id = 2;
"job_title" = Developer;
"last_name" = Prem;
location = "";
"phone_number" = "+6590091516";
"profile_pic" = "";
"thumbnail_profile_pic" = "";
"user_id" = 2;
}),
<User: 0xa25e460> (entity: User; id: 0xa25e4c0 <x-coredata:///User/t44BB97D0-C4B4-4BA6-BD25-13CEFDAE665F2> ; data: {
email = "sanchitbareja@gmail.com";
experience = "2013-07-20";
"first_name" = Sanchit;
id = 1;
"job_title" = Developer;
"last_name" = Bareja;
location = "";
"phone_number" = "+15106127328";
"profile_pic" = "";
"thumbnail_profile_pic" = "";
"user_id" = 1;
})
)}
当我尝试[managedObjectContext save:&error]
时,它成功并按预期打印出“保存的所有记录”。但是,当我转到我的应用程序.sqlite
文件并检查添加的对象时,我意识到它没有向数据库添加任何对象。
在应用程序重新启动时,我打印出数据库中已经存在的对象列表,它确认我还没有保存任何对象。
有谁知道发生了什么以及为什么我无法持久保存数据,即使看起来我已经成功创建了需要保存在核心数据模型中的“用户”对象。
编辑:
这是我创建的地方NSPersistentStoreCoordinator
// Returns the persistent store coordinator for the application.
// If the coordinator doesn't already exist, it is created and the application's store added to it.
- (NSPersistentStoreCoordinator *)persistentStoreCoordinator
{
if (_persistentStoreCoordinator != nil) {
return _persistentStoreCoordinator;
}
NSURL *storeURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:@"RTModel.sqlite"];
NSError *error = nil;
NSLog(@"Test 1");
_persistentStoreCoordinator = [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]];
NSLog(@"Test 2");
if (![_persistentStoreCoordinator addPersistentStoreWithType:NSSQLiteStoreType configuration:nil URL:storeURL options:nil error:&error]) {
/*
Replace this implementation with code to handle the error appropriately.
abort() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
Typical reasons for an error here include:
* The persistent store is not accessible;
* The schema for the persistent store is incompatible with current managed object model.
Check the error message to determine what the actual problem was.
If the persistent store is not accessible, there is typically something wrong with the file path. Often, a file URL is pointing into the application's resources directory instead of a writeable directory.
If you encounter schema incompatibility errors during development, you can reduce their frequency by:
* Simply deleting the existing store:
[[NSFileManager defaultManager] removeItemAtURL:storeURL error:nil]
* Performing automatic lightweight migration by passing the following dictionary as the options parameter:
[NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES], NSMigratePersistentStoresAutomaticallyOption, [NSNumber numberWithBool:YES], NSInferMappingModelAutomaticallyOption, nil];
Lightweight migration will only work for a limited set of schema changes; consult "Core Data Model Versioning and Data Migration Programming Guide" for details.
*/
NSLog(@"Unresolved error %@, %@", error, [error userInfo]);
abort();
}
return _persistentStoreCoordinator;
}
我有 3 个上下文。
masterManagedObjectContext
backgroundManagedObjectContext
newManagedObjectContext
master 是 background 和 new 的父级。当我查询这样的上下文时:
NSError *error = nil;
NSFetchRequest *request = [[NSFetchRequest alloc] initWithEntityName:@"User"];
[request setSortDescriptors:[NSArray arrayWithObject:
[NSSortDescriptor sortDescriptorWithKey:@"id" ascending:YES]]];
[request setReturnsObjectsAsFaults:NO];
NSArray *testArray = [[[RTCoreDataController sharedInstance] newManagedObjectContext] executeFetchRequest:request error:&error];
for (User *obj in testArray) {
NSLog(@"obj.id %@", obj.id);
}
NSLog(@"query records: %@",testArray);
master 和 background 都在 NSLog 中返回正确的 obj.id 并为@“query records”提供下面的输出
(
"<User: 0xa3811d0> (entity: User; id: 0xa381230 <x-coredata:///User/t92BCED2D-CD17-49CC-9EBA-DF8F52F06A002> ; data: {\n email = \"sanchitbareja@gmail.com\";\n experience = \"2013-07-20\";\n \"first_name\" = Sanchit;\n id = 1;\n \"job_title\" = Developer;\n \"last_name\" = Bareja;\n location = \"\";\n \"phone_number\" = \"+15106127328\";\n \"profile_pic\" = \"\";\n \"thumbnail_profile_pic\" = \"\";\n \"user_id\" = 1;\n})",
"<User: 0xa382170> (entity: User; id: 0xa3820b0 <x-coredata:///User/t92BCED2D-CD17-49CC-9EBA-DF8F52F06A003> ; data: {\n email = \"vishnu@vishnuprem.com\";\n experience = \"2013-07-20\";\n \"first_name\" = Vishnu;\n id = 2;\n \"job_title\" = Developer;\n \"last_name\" = Prem;\n location = \"\";\n \"phone_number\" = \"+6590091516\";\n \"profile_pic\" = \"\";\n \"thumbnail_profile_pic\" = \"\";\n \"user_id\" = 2;\n})"
)
但是“新”返回(null)
obj.id inNSLog
并返回以下内容@"query records"
:
(
"<User: 0xa2b08a0> (entity: User; id: 0x95aebe0 <x-coredata:///User/tBFCC6C5F-7D2C-4AA0-BA96-B806EE360A762> ; data: <fault>)",
"<User: 0xa2b0910> (entity: User; id: 0xa4b9780 <x-coredata:///User/tBFCC6C5F-7D2C-4AA0-BA96-B806EE360A763> ; data: <fault>)"
)