ios - 获取顶部约束的引用

Question

我正在尝试获取与安全区域 - 顶部关联的给定 View 的 topConstraint(例如:附加)的引用。

我创建了一个工作正常的函数，但逻辑上不可靠。

func getSafeAreaTopConstraint(view: UIView, in targetView: UIView) -> NSLayoutConstraint? {
    let constraints = targetView.constraints.filter({ $0.firstItem as? UIView == view || $0.secondItem as? UIView == view })
    return constraints.filter({ $0.firstAttribute == .top || $0.secondAttribute == .top }).first
}

我想创建一个比较如下的函数

func getSafeAreaTopConstraint(view: UIView, in targetView: UIView) -> NSLayoutConstraint? {
    let constraints = targetView.constraints.filter({ ($0.firstItem as? UIView == view && $0.secondItem == SafeArea.Top) || ($0.secondItem as? UIView == view && $0.firstItem == SafeArea.Top) })
    return constraints.filter({ $0.firstAttribute == .top || $0.secondAttribute == .top }).first
}

如何比较 firstItem 或 secondItem 是否为 Safe Area.Top？

Answer 1

您通过访问constraints字段所做的事情并不安全。推荐的方法是为约束创建 IBOutlet