Capture List

CaptureList.swift

import UIKit

final class Increment {
    
    // MARK: - Properties
    
    private var number: Int = 0
    
    // MARK: - This will cause memory leak
//    lazy var incrementNumber: (Int) -> Void = { value in
//        self.number += value
//        print(self.number)
//    }
    
    // MARK: - If I instantiate increment(), then I immediately call increment with a three, the program will crash, because when the stored property has returned, the object (increment instance) can be deallocated, nothing else is referring to it.

//    lazy var incrementNumber: (Int) -> Void = { [unowned self] value in
//        self.number += value
//        print(self.number)
//    }

    // MARK: - This will not cause memory leak

    lazy var incrementNumber: (Int) -> Void = { [weak self] value in
        guard let self = self else { print("Sorry I am did disappear") ; return }
        self.number += value
        print(self.number)
    }
    
    deinit {
        print(#function)
    }
}

// MARK: - Test

do {
    let increment = Increment().incrementNumber(3)
}

/*
 deinit
 Sorry I am did disappear
*/

do {
    let increment = Increment()
    increment.incrementNumber(3)
}

/*
 3
 deinit
*/