具有本地引用的结构与具有本地引用的类？ 迅捷的表现

Question

As far as I know if a struct contains more than one reference as property stored, it's (2*reference) more expensive to allocate it than a class. Is it the same case in local variables?

struct ViewNavigationRouter {

    private let firstViewController : UIViewController

    init(firstViewController: UIViewController) {
        self.firstViewController = firstViewController
    }

    func navigate(from: UIViewController) {

        let viewController1 : UIViewController = xxx
        let viewController2 : UIViewController = xxx
        let viewController3 : UIViewController = xxx
    }
}



class ViewNavigationRouter {

    private let firstViewController : UIViewController

    init(firstViewController: UIViewController) {
        self.firstViewController = firstViewController
    }

    func navigate(from: UIViewController) {

        let viewController1 : UIViewController = xxx
        let viewController2 : UIViewController = xxx
        let viewController3 : UIViewController = xxx
    }
}

Thanks in advance :)

Answer 1

It seems, it is the same in this case as all the members in struct ViewNavigationRouter and in class ViewNavigationRouter are - instances of classes (firstViewController : UIViewController). I do not see more wide context of this, but it looks like this here.

I suggest you to read this https://developer.apple.com/library/prerelease/content/documentation/Swift/Conceptual/Swift_Programming_Language/ClassesAndStructures.html many times, specially focusing to parts Structures and Enumerations Are Value Types and Classes Are Reference Types.

The most important difference is related to that what happends when you copy the content identifier is "pointing to". I suggest you further reading:

https://developer.apple.com/library/prerelease/content/documentation/Swift/Conceptual/Swift_Programming_Language/AutomaticReferenceCounting.htm and to tak a look to examples. Than you will see that difference is not about memory performance, but on the way how ARC clears memory.