Swift - Is dispatching to the main queue enough to make a var thread safe?

Question

When it comes to synchronization solutions, I know there are a lot of stuff I can use in order to make a var thread safe. But my question is this:

Since the main queue is serial, is dispatching to it enough to make a var safe for async reading/writing operations?

Let's say I have an Int array:

var myArr: [Int] = []

Whenever I need to update it i use the main queue:

let newVal = 123

dispatch_async(dispatch_get_main_queue(), { () -> Void in
    myArr.append(newVal)
})

And whenever I need to read from it:

dispatch_async(dispatch_get_main_queue(), { () -> Void in
    println(myArr.count)
})

Will that be enough to make myArr thread safe?

Answer 1

Yes, that is enough. As long as you read and write from the same serial queue you are safe.