ARC + Retain Cycle
理解程式是如何管控記憶體並且正確地操作物件,可以避免記憶體的浪費。
課程文件
如何找Retain Cycle
方法一:使用 deinit,確認物件是否被消滅
/// 人物
class People {
let name: String = "John"
var macbook: Macbook? = nil
deinit {
print("\(name) deinit.")
}
}
/// 筆電
class Macbook {
let name: String = "Macbook"
var owner: People? = nil
deinit {
print("\(name) deinit.")
}
}
方法二:使用 Xcode 的 Debug Memory Graphic

如何解決Retain Cycle
情境一: 兩個類別互相擁有,加上weak即可!!!
/// 人物
class People {
let name: String = "John"
var macbook: Macbook? = nil
deinit {
print("\(name) deinit.")
}
}
/// 筆電
class Macbook {
let name: String = "Macbook"
weak var owner: People? = nil // <----- 必須加上weak才可以被釋放
deinit {
print("\(name) deinit.")
}
}
情境二:Delegate和Protocol,加上weak即可!!!
protocol DataManagerDelegate: AnyObject {
func didGetData()
}
class DataManager{
weak var delegate: DataManagerDelegate? // <----- 必須加上weak才可以被釋放
func getData(){
delegate?.didGetData()
}
}
class ViewContorller: UIViewController{
private var dataManager = DataManager()
override func viewDidLoad() {
super.viewDidLoad()
dataManager.delegate = self
dataManager.getData()
}
}
extension ViewContorller: DataManagerDelegate{
func didGetData(){ ... }
}
情境三:被擁有的Closure,定義時請使用weak self即可!!!
class MemberManager{
var didChangeMember: ((String) -> Void)?
func changeMember(){
didChangeMember?("更換會員")
}
}
class TestClosure2ViewController: UIViewController {
var label = UILabel()
let memberManager = MemberManager()
override func viewDidLoad() {
super.viewDidLoad()
memberManager.didChangeMember = {
[weak self] value in // <----- Closure被Hold著,必須加上weak才可以被釋放
guard let self = self else { return }
self.label.text = value
}
memberManager.changeMember()
}
deinit {
print("TestClosure2 deinit.")
}
}
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