swift 关闭保留周期

Posted 2021-05-19

class HTMLElement {
    let name: String
    let text: String
    
    // 參考self的closure造成 記憶體無法釋放的retain cycle
    lazy var asHTML: () -> String = {
        return "<\(self.name)>\(self.text)</\(self.name)>"
    }

    init(name: String, text: String) {
        self.name = name
        self.text = text
    }
    
    deinit {
         print("HTMLElement \(name) is bring deallocated")
    }
}
var paragraph: HTMLElement? = HTMLElement(name: "p", text: "some smaple paragraph body text")

paragraph?.asHTML()
paragraph = nil // 因為retain cycle 而無法釋放所以不會執行 deinit