Ios 视图约束-拟合子视图

我正在向视图添加一个子视图，希望它填充视图的高度和宽度。我在约束方面有困难。感谢您的帮助。这就是我目前拥有的：

    self.view.addSubview(self.mainView)

    var leftSideConstraint = NSLayoutConstraint(item: self.mainView, attribute: .Left, relatedBy: .Equal, toItem: self.view, attribute: .Left, multiplier: 1.0, constant: 0.0)
    var bottomConstraint = NSLayoutConstraint(item: self.mainView, attribute: .Bottom, relatedBy: .Equal, toItem: self.view, attribute: .Bottom, multiplier: 1.0, constant: 0.0)
    var widthConstraint = NSLayoutConstraint(item: self.mainView, attribute: .Width, relatedBy: .Equal, toItem: self.view, attribute: .Width, multiplier: 1.0, constant: 0.0)
    var heightConstraint = NSLayoutConstraint(item: self.mainView, attribute: .Height, relatedBy: .Equal, toItem: self.view, attribute: .Height, multiplier: 1.0, constant: 0.0)
    self.view.addConstraints([leftSideConstraint, bottomConstraint, widthConstraint, heightConstraint])

---

以下代码应该可以工作：

    let mainView = UIView() //Make sure your mainView is initialized
    mainView.backgroundColor = UIColor.blueColor() //For test purpose

    mainView.setTranslatesAutoresizingMaskIntoConstraints(false) //Don't forget this line
    view.addSubview(mainView)

    var leftSideConstraint = NSLayoutConstraint(item: mainView, attribute: .Left, relatedBy: .Equal, toItem: view, attribute: .Left, multiplier: 1.0, constant: 0.0)
    var bottomConstraint = NSLayoutConstraint(item: mainView, attribute: .Bottom, relatedBy: .Equal, toItem: view, attribute: .Bottom, multiplier: 1.0, constant: 0.0)
    var widthConstraint = NSLayoutConstraint(item: mainView, attribute: .Width, relatedBy: .Equal, toItem: view, attribute: .Width, multiplier: 1.0, constant: 0.0)
    var heightConstraint = NSLayoutConstraint(item: mainView, attribute: .Height, relatedBy: .Equal, toItem: view, attribute: .Height, multiplier: 1.0, constant: 0.0)
    view.addConstraints([leftSideConstraint, bottomConstraint, heightConstraint, widthConstraint])

也可以使用自动布局视觉格式语言：

    let mainView = UIView() //Make sure your mainView is initialized
    mainView.backgroundColor = UIColor.blueColor() //For test purpose

    mainView.setTranslatesAutoresizingMaskIntoConstraints(false) //Don't forget this line
    view.addSubview(mainView)

    var viewsDict = ["mainView" : mainView]

    var horizontalConstraints = NSLayoutConstraint.constraintsWithVisualFormat("H:|[mainView]|", options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDict)
    var verticalConstraints = NSLayoutConstraint.constraintsWithVisualFormat("V:|[mainView]|", options: NSLayoutFormatOptions(0), metrics: nil, views: viewsDict)
    view.addConstraints(horizontalConstraints)
    view.addConstraints(verticalConstraints)

---

Swift 5

下面是一种使用UIView扩展的优雅方法

extension UIView {
    func addConstrained(subview: UIView) {
        addSubview(subview)
        subview.translatesAutoresizingMaskIntoConstraints = false
        subview.topAnchor.constraint(equalTo: topAnchor).isActive = true
        subview.leadingAnchor.constraint(equalTo: leadingAnchor).isActive = true
        subview.trailingAnchor.constraint(equalTo: trailingAnchor).isActive = true
        subview.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
    }
}

然后在需要的任何位置添加子视图

yourContainerView.addConstrained(subview: yourSubview)

---

谢谢我错过了setTranslatesAutoresizingMaskIntoConstraints电话。