如何设置UILayoutPriority？

Question

我尝试创建对约束的引用，然后设置布局优先级，但这会使应用程序崩溃

let topTrasactionConstraint = transactionsTableviewContainer.topAnchor.constraint(equalTo: buttonsStackContainerView.bottomAnchor, constant: 6)


    NSLayoutConstraint.activate([
            topTrasactionConstraint,
            transactionsTableviewContainer.centerXAnchor.constraint(equalTo: contentView.centerXAnchor),
            transactionsTableviewContainer.widthAnchor.constraint(equalTo: contentView.safeAreaLayoutGuide.widthAnchor, constant: -20),
            transactionsTableviewContainer.heightAnchor.constraint(equalToConstant: 500)
            ])


topTrasactionConstraint.priority = UILayoutPriority.init(999)

Answer 1

我发现我正在打电话

topTrasactionConstraint.priority = UILayoutPriority.init(999)

在此之前NSLayoutConstraint.activate
这导致我的应用程序崩溃