As the title says, the question is, if a NSManagedObjectContext with concurrency type NSPrivateQueueConcurrencyType is serial or concurrent.
More specifically, if I call
[managedObjectContext performBlock:^{
}];
with a long running task, will other calls to that context with performBlock be blocked until the first one finished?
It is serial queue from Apple docs.
Or you can simply try to run this code and see the result. The numbers will be printed serially.
let privateMOC = NSManagedObjectContext(concurrencyType: .privateQueueConcurrencyType)
privateMOC.perform {
for i in 0...8000 {
if i.isMultiple(of: 3000) {
print("1")
}
}
}
privateMOC.perform {
for i in 0...8000 {
if i.isMultiple(of: 3000) {
print("2")
}
}
}
It's a serial queue. You code will be performed serially when you call performBlock and performBlockAndWait if you specify NSPrivateQueueConcurrencyType.
Apple doesn't pick the word PrivateQueue randomly, Private Queue = Serial Queue in Apple's documents. See here for the Serial Queue description
Serial queues (also known as private dispatch queues) execute one task at a time in the order in which they are added to the queue.
Also, I have double checked that in debugging. Please see the last thread in the below screenshot:
I have tested that all tasks will be executed in sequence, but It may be executed in a different thread
backgroundContext.perform {
print("perform------:\(self.number)", Thread.current)
self.number += 1
}
