Escaping内のキャプチャ挙動確認用 via Playground

EscapingExams.swift

import UIKit

import UIKit

class HogeClass {
    let text = "weak"
    func print(handler: @escaping (String) -> Void) {
        DispatchQueue.main.asyncAfter(deadline: .now() + 1) { [weak self] in
            handler(self?.text ?? "")
        }
    }

    deinit {
        Swift.print("Bye, \(text)")
    }
}

var hoge: HogeClass? = .init()
hoge?.print(handler: { print("Hello, \($0)") })
hoge = nil

class HogeClass2 {
    let text = "strong"
    func print(handler: @escaping (String) -> Void) {
        DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
            handler(self.text)
        }
    }

    deinit {
        Swift.print("Bye, \(text)")
    }
}

var hoge2: HogeClass2? = .init()
hoge2?.print(handler: { print("Hello, \($0)") })
hoge2 = nil

class HogeClass3 {
    let text = "captured"
    func print(handler: @escaping (String) -> Void) {
        let txt = text
        DispatchQueue.main.asyncAfter(deadline: .now() + 1) {
            handler(txt)
        }
    }

    deinit {
        Swift.print("Bye, \(text)")
    }
}

var hoge3: HogeClass3? = .init()
hoge3?.print(handler: { print("Hello, \($0)") })
hoge3 = nil


//
// Results
//
// Bye, weak
// Bye, captured
// Hello,       <- weak but already released object.
// Hello, strong
// Bye, strong
// Hello, captured
//