Do you have to manually specify that your DispatchQueue is serial?-CodePudding

I know that you can create a concurrent queue by doing the following:

let queue = DispatchQueue(label: "My Awesome Queue", attributes: .concurrent)

But I don't see an alternative enum for creating serial queues, something like:

let queue = DispatchQueue(label: "My Awesome Queue", attributes: .serial)

The only other possible option seems to be .initiallyInactive, am I missing something?

How do I specify in Swift that I want a serial queue?

Note that I am using the above queues like this:

queue.async {
    // do task 1
}

queue.async {
    // do task 2
}

// expect task 1 to start
// expect task 1 to finish
// expect task 2 to start
// expect task 2 to finish

CodePudding user response：

let queue = DispatchQueue(label: "My Awesome Queue", attributes: .concurrent)

When you use DispatchQueue with .concurrent attribute. It will execute in a concurrent manner.

let queue = DispatchQueue(label: "My Awesome Queue")

But if this attribute is not present, the queue schedules tasks serially in first-in, first-out (FIFO) order. Check the documentation here for more details.

Btw : .initiallyInactive attribute is use to prevent the queue from scheduling blocks until you call its activate() method.

CodePudding user response：

Serial is the default. It isn't available as an option since if it was, you could specify both [.serial, .concurrent] which wouldn't make much sense. See here for more info.