我正在尝试保留新实体：
- (void)updateStorageWithQuizzess:(NSArray *)quizzess completion:(void(^)(NSArray *quizzess, BOOL succes, NSError *error))completion {
NSMutableArray *mutableArray = [NSMutableArray array];
[Quiz MR_truncateAll];
[[NSManagedObjectContext MR_context] MR_saveWithBlock:^(NSManagedObjectContext *localContext) {
for (NSDictionary *dictionary in quizzess) {
Quiz *quiz = [Quiz MR_createEntity];
[quiz fromDictionary:dictionary];
[mutableArray addObject:quiz];
}
} completion:^(BOOL contextDidSave, NSError *error) {
BlockSafeRun(completion, mutableArray, contextDidSave, error);
}];
}
或像这样：
- (void)updateStorageWithQuizzess:(NSArray *)quizzess completion:(void(^)(NSArray *quizzess, BOOL succes, NSError *error))completion {
NSMutableArray *mutableArray = [NSMutableArray array];
[Quiz MR_truncateAll];
[MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {
for (NSDictionary *dictionary in quizzess) {
Quiz *quiz = [Quiz MR_createEntity];
[quiz fromDictionary:dictionary];
[mutableArray addObject:quiz];
}
} completion:^(BOOL contextDidSave, NSError *error) {
BlockSafeRun(completion, mutableArray, contextDidSave, error);
}];
}
但是在完成块中，我收到contextDidSave == NO，错误== nil。因此，我无法弄清楚出了什么问题。我犯了一些明显的错误吗？如何调试该问题？
//////
2015-06-17 20:39:27.061 HITO[6733:618953] Set root saving context: <NSManagedObjectContext: 0x16dbe070>
2015-06-17 20:39:27.062 HITO[6733:618953] Created new main queue context: <NSManagedObjectContext: 0x16e855b0>
2015-06-17 20:39:27.063 HITO[6733:618953] Set default context: <NSManagedObjectContext: 0x16e855b0>
2015-06-17 20:39:27.316 HITO[6733:618953] [HockeySDK] WARNING: Detecting crashes is NOT enabled due to running the app with a debugger attached.
2015-06-17 20:39:28.829 HITO[6733:618953] Created new private queue context: <NSManagedObjectContext: 0x16d57870>
2015-06-17 20:39:28.831 HITO[6733:619027] Created new private queue context: <NSManagedObjectContext: 0x16ea4ec0>
2015-06-17 20:39:28.841 HITO[6733:619027] NO CHANGES IN ** saveWithBlock:completion: ** CONTEXT - NOT SAVING
更新
以下来自MR的代码：
- (void) MR_saveWithOptions:(MRSaveOptions)saveOptions completion:(MRSaveCompletionHandler)completion;
{
__block BOOL hasChanges = NO;
if ([self concurrencyType] == NSConfinementConcurrencyType)
{
hasChanges = [self hasChanges];
}
else
{
[self performBlockAndWait:^{
hasChanges = [self hasChanges];
}];
}
if (!hasChanges)
{
MRLogVerbose(@"NO CHANGES IN ** %@ ** CONTEXT - NOT SAVING", [self MR_workingName]);
if (completion)
{
dispatch_async(dispatch_get_main_queue(), ^{
completion(NO, nil);
});
}
return;
}
因此，hasChanges返回NO。
您的对象在保存块中没有发生任何更改。我在这里看到两个问题。
MR_defaultContext需要在时创建新对象，localContext这是保存块的保存上下文。尝试这个：
- (void)updateStorageWithQuizzess:(NSArray *)quizzess completion:(void(^)(NSArray *quizzess, BOOL succes, NSError *error))completion {
NSMutableArray *mutableArray = [NSMutableArray array];
[MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {
for (NSDictionary *dictionary in quizzess) {
Quiz *quiz = [Quiz MR_createInContext:localContext];
[quiz fromDictionary:dictionary];
[mutableArray addObject:quiz];
}
} completion:^(BOOL contextDidSave, NSError *error) {
BlockSafeRun(completion, mutableArray, contextDidSave, error);
}];
}
[Quiz MR_truncateAll]只需将所有Quizobjectsdeleted属性设置为即可true。这意味着下次保存或处理上下文时，更改将被保存。
因此，当您创建新的保存上下文时，该上下文仍然具有那些对象。我不确定您的fromDictionary方法在做什么，但是如果它依赖数据库，那么它就不会拥有它。
您需要这样做：
- (void)updateStorageWithQuizzess:(NSArray *)quizzess completion:(void(^)(NSArray *quizzess, BOOL succes, NSError *error))completion {
NSMutableArray *mutableArray = [NSMutableArray array];
[MagicalRecord saveWithBlock:^(NSManagedObjectContext *localContext) {
[Quiz MR_truncateAllInContext:localContext];
[localContext processPendingChanges];
for (NSDictionary *dictionary in quizzess) {
Quiz *quiz = [Quiz MR_createInContext:localContext];
[quiz fromDictionary:dictionary];
[mutableArray addObject:quiz];
}
} completion:^(BOOL contextDidSave, NSError *error) {
BlockSafeRun(completion, mutableArray, contextDidSave, error);
}];
}
这样，您将在保存上下文中删除对象。您还必须记住调用processPendingChanges保存上下文从上下文中删除对象，而不仅仅是将它们标记为要删除。
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我来说两句