CODEWITHSUNDEEP
swiftfunctionclosuresautomatic-ref-counting
Won
Won

Reputation: 1226

capture list for function in swift

When use closure we can avoid strong reference cycle by using weak or unowned for capture list.

I know that the function is also a named closure. So I guess function also capture values from the context.

How can I avoid strong reference cycle for function?

Codes below

class Person {
    var name: String?

    func printInfo() {
        print(self.name ?? "nil")
    }

    deinit {
         print("\(self.name ?? "") is deinitialized.")
    }
}

var p1: Person? = Person()
p1?.name = "Person1"

var printFunction = p1?.printInfo
p1 = nil

Not print any message

...
p1 = nil
printFunction = nil

print Person1 is deinitialized.

Does anyone have a solution to this case? In closure case we have weak, unowned capture list.

Upvotes: 1

Views: 744

Answers (1)

flowGlen
flowGlen

Reputation: 687

You can replace the method with a closure.

class Person {
    var name: String?

    lazy var printInfo = { [unowned self] in
        print(self.name ?? "nil")
    }

    deinit {
        print("\(self.name ?? "") is deinitialized.")
    }
}


var p1: Person? = Person()
p1?.name = "Person1"

var printFunction = p1?.printInfo

p1 = nil

This code print - Person1 is deinitialized.

lazy ensures that the access to the property will occur exactly after the initialization of the instance, so the self will definitely exist and we can use the self in the closure body. if you need more information read about ARC - https://docs.swift.org/swift-book/LanguageGuide/AutomaticReferenceCounting.html

Upvotes: 1

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