Weak self

class DoTaskClass {
    
    let identifier: String
    
    init(identifier: String) {
        self.identifier = identifier
    }
    
    func getTask() -> (() -> ()) {
        return { [weak self] in
            withUnsafePointer(to: &self) {
                print("Optional self \(self) has address: \($0)")
            }
            
            if var this = self {
                print("DoTaskClass::getTask identifier \(this.identifier)")
                withUnsafePointer(to: &this) {
                    print("Optional self \(this) has address: \($0)")
                }
            }
            print("\n")
        }
    }
    
    deinit {
        print(" \(identifier) ☠️ \n")
    }
    
}

do {
    print("_______________ Case 1 _______________")
    func replace(_ p: UnsafeMutablePointer<DoTaskClass>) {
        var pointer = p
        //    print("before \(pointer.pointee.identifier)") //This will couse a crash EXC_BAD_ACCESS if pointer.pointee is nil
        pointer.pointee = DoTaskClass(identifier: "---2---")
        print("after \(pointer.pointee.identifier)\n")
    }
    
    var taskHolder: DoTaskClass? = DoTaskClass(identifier: "___1___")
    
    let task = taskHolder!.getTask()
    task()
    
    var pointer = UnsafeMutablePointer(&taskHolder!)
    taskHolder = nil
    
    task()
    replace(pointer)
    task()
}

do {
    print("_______________ Case 2 _______________")
    func replace(_ p: UnsafeMutablePointer<DoTaskClass>) {
        var pointer = p
        //    print("before \(pointer.pointee.identifier)") //This will couse a crash EXC_BAD_ACCESS if pointer.pointee is nil
        pointer.pointee = DoTaskClass(identifier: "---2---")
        print("after \(pointer.pointee.identifier)\n")
    }
    
    var taskHolder: DoTaskClass? = DoTaskClass(identifier: "___1___")
    
    let task = taskHolder!.getTask()
    task()
    
    var pointer = UnsafeMutablePointer(&taskHolder!)

    replace(pointer)
    task()
}