CODEWITHSUNDEEP
iosswiftmultithreadingsprite-kitgrand-central-dispatch
Pop Flamingo
Pop Flamingo

Reputation: 2191

Is SKNode thread safe?

On an iOS game I am making with Swift, I am listening to touch events, reading the userDataproperty of some SKNode, and updating the texture property of some other SKSpriteNode that are part of the scene, but to avoid any lag during the user interaction, I dispatch this update code asynchronously on the main queue, is it a good idea ?

By the way, some general question about thread safety : is there a risk only when you are writing data, or is there also a risk when reading data ?

Thank you.

Upvotes: 2

Views: 275

Answers (1)

kelin
kelin

Reputation: 12001

As current documentation on SKNode says in getting started section:

Ensure Node Access on the Main Thread

So, the answer for the question in the title

Is SKNode thread safe?

is - NO. SKNode isn't thread safe, it should be modified only from the main thread.

But the answer for the second question:

I dispatch this update code asynchronously on the main queue, is it a good idea?

will be YES. It's exactly what you expected to do.

As for the last question: risk is possible when reading data. If you read a constant like let version = 3, there will be no risk. But take a look at this example:

var bigLazyObject: BigObject?

func getBigLazyObject() -> BigObject {
    if let existingObject = bigLazyObject {
        return existingObject
    } else {
        let newObject = BigObject()
        bigLazyObject = newObject
        return newObject
    }
}

It demonstrates an unwanted creation of the second BigObject instance, which can occure if getBigLazyObject() will be called in 2 threads simultaneously. There is a chance that both threads will fall in the else branch of the if statement before bigLazyObject is actually created. This kind of problem should be solved when creating thread-safe singletons. In Swift they are thread-safe buy default, but in Objective-C people usually use dispatch_once() block.

Upvotes: 1

Related Questions