Better way of using "self." in background thread?

Question

After adding DispatchQueue.global(qos: .background).async {} to a single function of my code (Xcode 10, Swift 5), the scrollbar looks like this:

These are more than 40 calls to vars and other funcs that need a "self.".

Fixing this isn't hard (Editor > Fix All Issues) but it reduces readability a lot.

I'm aware that it's possible to create new copies of/references to these vars and using them instead of the ones outside but then there'll be a lot of new copies/references.

Is there a third way of fixing this that helps with readability but doesn't change the initial code (too much)?

Answer 1

You can create a nested function or another method to put the code you want to execute in, then pass that nested function or method into DispatchQueue.main.async.

Here's an example with a nested function:

Original code:

class Foo {
    var a = 0
    var b = 0
    var c = 0

    func f() {
        a = 1
        b = 1
        c = 1
    }
}

Doing it asynchronously:

class Foo {
    var a = 0
    var b = 0
    var c = 0

    func f() {
        func doAsync() {
            a = 1
            b = 1
            c = 1
        }
        DispatchQueue.global(qos: .background).async(execute: doAsync)
    }
}

As you can see, you don't need to add any selfs.