如何以编程方式将约束添加到 UISegmentedControl

Question

这是我的 UISegmentedControl 代码：

   employeeSegmentedControl = UISegmentedControl(items: items)
    employeeSegmentedControl.selectedSegmentIndex = 0
    employeeSegmentedControl.backgroundColor = UIColor(red: 41/255, green: 128/255, blue: 185/255, alpha: 1.0)
    employeeSegmentedControl.tintColor = UIColor.whiteColor()
    employeeSegmentedControl.addTarget(self, action: Selector("indexChanged:"), forControlEvents: .ValueChanged)
    self.view.addSubview(employeeSegmentedControl)

    employeeSegmentedControl.setTranslatesAutoresizingMaskIntoConstraints(false)
    self.view.addConstraint(NSLayoutConstraint(item: employeeSegmentedControl, attribute: .Width, relatedBy: .Equal, toItem: self.view, attribute: .Width, multiplier: 1.0, constant: 0.0))
    self.view.addConstraint(NSLayoutConstraint(item: employeeSegmentedControl, attribute: .Height, relatedBy: .Equal, toItem: self.searchController.searchBar, attribute: .Height, multiplier: 1.0, constant: 0.0))
    self.view.addConstraint(NSLayoutConstraint(item: employeeSegmentedControl, attribute: .CenterX, relatedBy: .Equal, toItem: self.view, attribute: .CenterX, multiplier: 1.0, constant: 0.0))
    self.view.addConstraint(NSLayoutConstraint(item: employeeSegmentedControl, attribute: .CenterY, relatedBy: .Equal, toItem: self.searchController.searchBar, attribute: .CenterY, multiplier: 1.2, constant: 0.0))

如您所见，我正在向 UISegmentedControl 添加约束，但我的应用程序崩溃了。这是我的错误信息：

2015-09-03 18:50:52.241 Employee Keeper[14424:11105086] * 由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“* +[NSLayoutConstraint constraintWithItem:attribute:relatedBy :toItem:attribute:multiplier:constant:]: 乘数 0 或 nil 第二项与第一个属性的位置一起创建一个非法的位置约束等于一个常量。位置属性必须成对指定' *** 首先抛出调用栈：

我做错了什么？

Answer 1

我认为这是因为设置约束时您的 self.searchController.searchBar 为零