ios - 更新约束不适用于 UITableView snapkit

Question

当我尝试在创建约束后立即更新 snapkit 约束时，我得到一个Updated constraint could not find existing matching constraint to update 错误。我使用的代码如下:

let directionList = UITableView()
directionList.delegate = self
directionList.dataSource = self
directionList.tag = DIRECTIONS_TABLE_TAG
self.view.addSubview(directionList)
directionList.snp.makeConstraints{ (make) -> Void in
    make.width.equalToSuperview()
    make.top.equalTo(self.view.snp.bottom)
    make.left.equalToSuperview()
    make.right.equalToSuperview()
    make.bottom.equalToSuperview().offset(-20)
}

directionList.snp.updateConstraints { (make) -> Void in
   make.top.equalTo(self.topDarkBlue.snp.bottom)
}

Answer 1

documentation表示 updateConstraints 仅用于更新现有约束的常量。

Alternative if you are only updating the constant value of the constraint you can use the method snp.updateConstraints instead of snp.makeConstraints

您没有更新常量；您正在尝试将约束分配给新的 anchor 。

我认为你应该做的是引用顶部约束:

var topConstraint: Constraint? = nil
...
topConstraint = make.top.equalTo(self.view.snp.bottom)

稍后移除顶部约束:

topConstraint.uninstall()

然后使用另一个 block 来制作新的约束。

directionList.snp.makeConstraints{ (make) -> Void in
   make.top.equalTo(self.topDarkBlue.snp.bottom)
}