weak.swift

// MARK: - weak reference
weak var weakCustomer1stRef: Customer? = nil
weak var weakCustomer2stRef: Customer? = nil

weakCustomer1stRef = Customer(udid: "weak 1", name: "Jacob")
/*
 print: weak 1 initialized
 print: weak 1 deinitialized
 */

/*
 That is deallocated right after initialization because haven't any strong reference.
 weakCustomer1stRef is nil
 */

var strongCustomerRef: Customer? = Customer(udid: "strong 1", name: "Klo")
/*
 strong 1 initialized
 */
weakCustomer1stRef = strongCustomerRef
weakCustomer2stRef = weakCustomer1stRef

print("weak 1st: \(String(describing: weakCustomer1stRef))")
print("weak 2nd: \(String(describing: weakCustomer2stRef))")
/*
 Both weak references are not nil
 */

strongCustomerRef = nil
/*
 print: strong 1 deinitialized
 */
print("weak 1st: \(String(describing: weakCustomer1stRef))")
print("weak 2nd: \(String(describing: weakCustomer2stRef))")
/*
 strongCustomerRef is setup to nil
 Both weak references will be setup to nil at runtime
 */