Swift 懶加載

1.常見懶加載方法

class ViewController: UIViewController {
    
    lazy var label: UILabel = {
        let label = UILabel(frame: .zero)
        label.translatesAutoresizingMaskIntoConstraints = false
        label.textColor = .black
        label.font = UIFont.systemFont(ofSize: 16, weight: .bold)
        return label
    }()
}

 

2.懶加載使用weak  還是 unowned？

[weak self]  in

還是用
[unowned self]  in

如果你能保證在使用過程中引用對象不會為nil，用unowned 。如果不能，那么就用weak

 

3.工廠方法 + 懶加載

是

class ViewController: UIViewController {
    
    lazy var label: UILabel = self.createCustomLabel()

    private func createCustomLabel() -> UILabel {
        print("被調用")
        let label = UILabel(frame: .zero)
        label.translatesAutoresizingMaskIntoConstraints = false
        label.textColor = .black
        label.font = UIFont.systemFont(ofSize: 16, weight: .bold)
        return label
    }
}

 

4.如果希望在多處使用，使用靜態工廠 + 懶加載

class ViewController: UIViewController {
    
    lazy var label: UILabel = UILabel.createCustomLabel()
}

extension UILabel {

    static func createCustomLabel() -> UILabel {
        let label = UILabel(frame: .zero)
        label.translatesAutoresizingMaskIntoConstraints = false
        label.textColor = .black
        label.font = UIFont.systemFont(ofSize: 16, weight: .bold)
        return label
    }
}