核心数据:save和fetch的并发冲突
Core data: concurency conflict between save and fetch
这两个函数调用似乎有冲突:
MagicalRecord.save({ (localContext) in
let items = NewsItem.staleNewsItems(in: localContext)
if ((items?.count)! > 0){
items?.forEach({ (item) in
if let object = item as? NSManagedObject {
object.mr_deleteEntity(in: localContext)
}
})
}
})
和
- (void) buildAndFetchFRCsInContext:(NSManagedObjectContext*)context {
self.newsItemsFRC = [self buildFetchResultsControllerForClass:[NewsItem class] sortedBy:@"id" withPredicate:nil inContext:context];
[context performBlock:^{
__unused NSDate* start = [NSDate date];
NSError* error;
[self.newsItemsFRC performFetch:&error]; // this line crashes
[self calculateAndBroadcastCounts];
}];
}
这个保存调用线程安全吗?如果是这样,是什么导致这两个函数相互崩溃?
问题是我在创建它们的上下文之外修改新闻项。因此,为了解决这个问题,我不得不将代码移至主线程。我从使用神奇的记录保存切换到只使用 performBlockAndWait,它保证在调用线程上 运行:
private static func cleanUpNewsItems() -> Void {
let context = NSManagedObjectContext.mr_()
context.performAndWait {
var itemsToDelete = [NSManagedObject]()
if let items = NewsItem.staleNewsItems(in: context) {
items.forEach({ (item) in
itemsToDelete.append(item as! NSManagedObject)
})
}
for item in itemsToDelete {
context.delete(item)
}
do {
try context.save()
} catch let error as NSError {
print("Error While Deleting Note: \(error.userInfo)")
}
}
}
这两个函数调用似乎有冲突:
MagicalRecord.save({ (localContext) in
let items = NewsItem.staleNewsItems(in: localContext)
if ((items?.count)! > 0){
items?.forEach({ (item) in
if let object = item as? NSManagedObject {
object.mr_deleteEntity(in: localContext)
}
})
}
})
和
- (void) buildAndFetchFRCsInContext:(NSManagedObjectContext*)context {
self.newsItemsFRC = [self buildFetchResultsControllerForClass:[NewsItem class] sortedBy:@"id" withPredicate:nil inContext:context];
[context performBlock:^{
__unused NSDate* start = [NSDate date];
NSError* error;
[self.newsItemsFRC performFetch:&error]; // this line crashes
[self calculateAndBroadcastCounts];
}];
}
这个保存调用线程安全吗?如果是这样,是什么导致这两个函数相互崩溃?
问题是我在创建它们的上下文之外修改新闻项。因此,为了解决这个问题,我不得不将代码移至主线程。我从使用神奇的记录保存切换到只使用 performBlockAndWait,它保证在调用线程上 运行:
private static func cleanUpNewsItems() -> Void {
let context = NSManagedObjectContext.mr_()
context.performAndWait {
var itemsToDelete = [NSManagedObject]()
if let items = NewsItem.staleNewsItems(in: context) {
items.forEach({ (item) in
itemsToDelete.append(item as! NSManagedObject)
})
}
for item in itemsToDelete {
context.delete(item)
}
do {
try context.save()
} catch let error as NSError {
print("Error While Deleting Note: \(error.userInfo)")
}
}
}