如果你想要填充你的超级视图，那么我建议快速的方法:

view.translatesAutoresizingMaskIntoConstraints = false
let attributes: [NSLayoutAttribute] = [.top, .bottom, .right, .left]
NSLayoutConstraint.activate(attributes.map {
    NSLayoutConstraint(item: view, attribute: $0, relatedBy: .equal, toItem: view.superview, attribute: $0, multiplier: 1, constant: 0)
})

否则，如果你需要非相等的约束检查NSLayoutAnchor作为iOS 9。使用NSLayoutConstraint直接读取通常要容易得多:

view.translatesAutoresizingMaskIntoConstraints = false
view.topAnchor.constraint(equalTo: view.superview!.topAnchor).isActive = true
view.bottomAnchor.constraint(equalTo: view.superview!.bottomAnchor).isActive = true
view.leadingAnchor.constraint(equalTo: view.superview!.leadingAnchor, constant: 10).isActive = true
view.trailingAnchor.constraint(equalTo: view.superview!.trailingAnchor, constant: 10).isActive = true

尝试这个优雅的UIView扩展约束。你可以简单地做约束:

 - firstView.coverWholeSuperview()
 - firstView.constraints(size: CGSize(width: 44, height: 44), centerX: view.centerXAnchor, centerY: view.centerXAnchor)
 - firstView.constraints(top: view.topAnchor, 
                         leading: secondView.leadingAnchor, 
                         bottom: view.bottomAnchor, 
                         trailing: secondView.trailingAnchor, 
                         padding: UIEdgeInsets(top: 12, left: 12, bottom: 12, right: 12))

这里是扩展，只需复制到您的项目。

extension UIView {
    /// Attaches all sides of the receiver to its parent view
    func coverWholeSuperview(margin: CGFloat = 0.0) {
        let view = superview
        layoutAttachTop(to: view, margin: margin)
        layoutAttachBottom(to: view, margin: margin)
        layoutAttachLeading(to: view, margin: margin)
        layoutAttachTrailing(to: view, margin: margin)

    }

    /// Attaches the top of the current view to the given view's top if it's a superview of the current view
    /// or to it's bottom if it's not (assuming this is then a sibling view).
    @discardableResult
    func layoutAttachTop(to: UIView? = nil, margin: CGFloat = 0.0) -> NSLayoutConstraint {

        let view: UIView? = to ?? superview
        let isSuperview = view == superview
        let constraint = NSLayoutConstraint(item: self, attribute: .top, relatedBy: .equal,
                                            toItem: view, attribute: isSuperview ? .top : .bottom, multiplier: 1.0,
                                            constant: margin)
        superview?.addConstraint(constraint)

        return constraint
    }

    /// Attaches the bottom of the current view to the given view
    @discardableResult
    func layoutAttachBottom(to: UIView? = nil, margin: CGFloat = 0.0, priority: UILayoutPriority? = nil) -> NSLayoutConstraint {

        let view: UIView? = to ?? superview
        let isSuperview = (view == superview) || false
        let constraint = NSLayoutConstraint(item: self, attribute: .bottom, relatedBy: .equal,
                                            toItem: view, attribute: isSuperview ? .bottom : .top, multiplier: 1.0,
                                            constant: -margin)
        if let priority = priority {
            constraint.priority = priority
        }
        superview?.addConstraint(constraint)

        return constraint
    }

    /// Attaches the leading edge of the current view to the given view
    @discardableResult
    func layoutAttachLeading(to: UIView? = nil, margin: CGFloat = 0.0) -> NSLayoutConstraint {

        let view: UIView? = to ?? superview
        let isSuperview = (view == superview) || false
        let constraint = NSLayoutConstraint(item: self, attribute: .leading, relatedBy: .equal,
                                            toItem: view, attribute: isSuperview ? .leading : .trailing, multiplier: 1.0,
                                            constant: margin)
        superview?.addConstraint(constraint)

        return constraint
    }

    /// Attaches the trailing edge of the current view to the given view
    @discardableResult
    func layoutAttachTrailing(to: UIView? = nil, margin: CGFloat = 0.0, priority: UILayoutPriority? = nil) -> NSLayoutConstraint {

        let view: UIView? = to ?? superview
        let isSuperview = (view == superview) || false
        let constraint = NSLayoutConstraint(item: self, attribute: .trailing, relatedBy: .equal,
                                            toItem: view, attribute: isSuperview ? .trailing : .leading, multiplier: 1.0,
                                            constant: -margin)
        if let priority = priority {
            constraint.priority = priority
        }
        superview?.addConstraint(constraint)

        return constraint
    }

    // For anchoring View
    struct AnchoredConstraints {
        var top, leading, bottom, trailing, width, height, centerX, centerY: NSLayoutConstraint?
    }

    @discardableResult
    func constraints(top: NSLayoutYAxisAnchor? = nil, leading: NSLayoutXAxisAnchor? = nil, bottom: NSLayoutYAxisAnchor? = nil,
                trailing: NSLayoutXAxisAnchor? = nil, padding: UIEdgeInsets = .zero, size: CGSize = .zero,
                centerX: NSLayoutXAxisAnchor? = nil, centerY: NSLayoutYAxisAnchor? = nil,
                centerXOffset: CGFloat = 0, centerYOffset: CGFloat = 0) -> AnchoredConstraints {

        translatesAutoresizingMaskIntoConstraints = false
        var anchoredConstraints = AnchoredConstraints()

        if let top = top {
            anchoredConstraints.top = topAnchor.constraint(equalTo: top, constant: padding.top)
        }

        if let leading = leading {
            anchoredConstraints.leading = leadingAnchor.constraint(equalTo: leading, constant: padding.left)
        }

        if let bottom = bottom {
            anchoredConstraints.bottom = bottomAnchor.constraint(equalTo: bottom, constant: -padding.bottom)
        }

        if let trailing = trailing {
            anchoredConstraints.trailing = trailingAnchor.constraint(equalTo: trailing, constant: -padding.right)
        }

        if size.width != 0 {
            anchoredConstraints.width = widthAnchor.constraint(equalToConstant: size.width)
        }

        if size.height != 0 {
            anchoredConstraints.height = heightAnchor.constraint(equalToConstant: size.height)
        }

        if let centerX = centerX {
            anchoredConstraints.centerX = centerXAnchor.constraint(equalTo: centerX, constant: centerXOffset)
        }

        if let centerY = centerY {
            anchoredConstraints.centerY = centerYAnchor.constraint(equalTo: centerY, constant: centerYOffset)
        }

        [anchoredConstraints.top, anchoredConstraints.leading, anchoredConstraints.bottom,
         anchoredConstraints.trailing, anchoredConstraints.width,
         anchoredConstraints.height, anchoredConstraints.centerX,
         anchoredConstraints.centerY].forEach { $0?.isActive = true }

        return anchoredConstraints
    }
}

它帮助我直观地学习，所以这是一个补充答案。

样板代码

override func viewDidLoad() {
    super.viewDidLoad()

    let myView = UIView()
    myView.backgroundColor = UIColor.blue
    myView.translatesAutoresizingMaskIntoConstraints = false
    view.addSubview(myView)

    // Add constraints code here
    // ...
}

下面的每个例子都是相互独立的。

引脚左边缘

myView。leading = leadingMargin + 20

方法1:锚式

let margins = view.layoutMarginsGuide
myView.leadingAnchor.constraint(equalTo: margins.leadingAnchor, constant: 20).isActive = true

除了leadingAnchor，还有trailingAnchor, topAnchor和bottomAnchor。

方法2:NSLayoutConstraint样式

NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.leading, relatedBy: NSLayoutRelation.equal, toItem: view, attribute: NSLayoutAttribute.leadingMargin, multiplier: 1.0, constant: 20.0).isActive = true

除了。leading，还有。tailed，。top，和。bottom。 除了。leadingmargin，还有。trailingmargin， . topmargin和.bottom margin。

设置宽度和高度

宽度= 200 高度= 100

方法1:锚式

myView.widthAnchor.constraint(equalToConstant: 200).isActive = true
myView.heightAnchor.constraint(equalToConstant: 100).isActive = true

方法2:NSLayoutConstraint样式

NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.width, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 200).isActive = true
NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 100).isActive = true

集装箱中心

myView。centerX = centerX myView。世纪=世纪

方法1:锚式

myView.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
myView.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

方法2:NSLayoutConstraint样式

NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.centerX, relatedBy: NSLayoutRelation.equal, toItem: view, attribute: NSLayoutAttribute.centerX, multiplier: 1, constant: 0).isActive = true
NSLayoutConstraint(item: myView, attribute: NSLayoutAttribute.centerY, relatedBy: NSLayoutRelation.equal, toItem: view, attribute: NSLayoutAttribute.centerY, multiplier: 1, constant: 0).isActive = true

笔记

锚的风格是首选的方法超过NSLayoutConstraint风格，但它只适用于iOS 9，所以如果你是支持iOS 8，那么你仍然应该使用NSLayoutConstraint风格。 上面的例子只显示了我们所关注的一两个约束条件。然而，为了在我的测试项目中正确地放置myView，我需要有四个约束。

进一步的阅读

以编程方式创建约束文档

    var xCenterConstraint : NSLayoutConstraint!
    var yCenterConstraint: NSLayoutConstraint!

 xCenterConstraint = NSLayoutConstraint(item: self.view, attribute: .CenterX, relatedBy: .Equal, toItem: (Your view NAme), attribute: .CenterX, multiplier: 1, constant: 0)
            self.view.addConstraint(xCenterConstraint)

 yCenterConstraint = NSLayoutConstraint(item: self.view, attribute: .CenterY, relatedBy: .Equal, toItem: (Your view Name), attribute: .CenterY, multiplier: 1, constant: 0)
            self.view.addConstraint(yCenterConstraint)

这是一种以编程方式添加约束的方法

override func viewDidLoad() {
            super.viewDidLoad()


let myLabel = UILabel()
        myLabel.labelFrameUpdate(label: myLabel, text: "Welcome User", font: UIFont(name: "times new roman", size: 40)!, textColor: UIColor.red, textAlignment: .center, numberOfLines: 0, borderWidth: 2.0, BorderColor: UIColor.red.cgColor)
        self.view.addSubview(myLabel)


         let myLabelhorizontalConstraint = NSLayoutConstraint(item: myLabel, attribute: NSLayoutAttribute.centerX, relatedBy: NSLayoutRelation.equal, toItem: self.view, attribute: NSLayoutAttribute.centerX, multiplier: 1, constant: 0)
        let myLabelverticalConstraint = NSLayoutConstraint(item: myLabel, attribute: NSLayoutAttribute.centerY, relatedBy: NSLayoutRelation.equal, toItem: self.view, attribute: NSLayoutAttribute.centerY, multiplier: 1, constant: 0)
        let mylabelLeading = NSLayoutConstraint(item: myLabel, attribute: NSLayoutAttribute.leading, relatedBy: NSLayoutRelation.equal, toItem: self.view, attribute: NSLayoutAttribute.leading, multiplier: 1, constant: 10)
        let mylabelTrailing = NSLayoutConstraint(item: myLabel, attribute: NSLayoutAttribute.trailing, relatedBy: NSLayoutRelation.equal, toItem: self.view, attribute: NSLayoutAttribute.trailing, multiplier: 1, constant: -10)
        let myLabelheightConstraint = NSLayoutConstraint(item: myLabel, attribute: NSLayoutAttribute.height, relatedBy: NSLayoutRelation.equal, toItem: nil, attribute: NSLayoutAttribute.notAnAttribute, multiplier: 1, constant: 50)
        NSLayoutConstraint.activate(\[myLabelhorizontalConstraint, myLabelverticalConstraint, myLabelheightConstraint,mylabelLeading,mylabelTrailing\])
}

extension UILabel
{
    func labelFrameUpdate(label:UILabel,text:String = "This is sample Label",font:UIFont = UIFont(name: "times new roman", size: 20)!,textColor:UIColor = UIColor.red,textAlignment:NSTextAlignment = .center,numberOfLines:Int = 0,borderWidth:CGFloat = 2.0,BorderColor:CGColor = UIColor.red.cgColor){
        label.translatesAutoresizingMaskIntoConstraints = false
        label.text = text
        label.font = font
        label.textColor = textColor
        label.textAlignment = textAlignment
        label.numberOfLines = numberOfLines
        label.layer.borderWidth = borderWidth
        label.layer.borderColor = UIColor.red.cgColor
    }
}

通过对图像施加约束来实现自动布局。使用NSLayoutConstraint。我们可以在所有设备上实现理想而漂亮的设计。请尝试下面的代码。

import UIKit

class ViewController: UIViewController {

override func viewDidLoad() {
super.viewDidLoad()

let myImageView:UIImageView = UIImageView()
myImageView.backgroundColor = UIColor.red
myImageView.image = UIImage(named:"sample_dog")!
myImageView.translatesAutoresizingMaskIntoConstraints = false
myImageView.layer.borderColor = UIColor.red.cgColor
myImageView.layer.borderWidth = 10
self.view.addSubview(myImageView)
        
view.removeConstraints(view.constraints)


view.addConstraint(NSLayoutConstraint(
item: myImageView,
attribute: .top,
relatedBy: .equal,
toItem: view,
attribute: .top,
multiplier: 1,
constant:100)
    
)

view.addConstraint(NSLayoutConstraint(
item: myImageView,
attribute: .centerX,
relatedBy: .equal,
toItem: view,
attribute: .centerX,
multiplier: 1,
constant:0)
)
    
view.addConstraint(NSLayoutConstraint(
item: myImageView,
attribute: .height,
relatedBy: .equal,
toItem: view,
attribute: .width,
multiplier: 0.5,
constant:40))
    
view.addConstraint(NSLayoutConstraint(
item: myImageView,
attribute: .width,
relatedBy: .equal,
toItem: view,
attribute: .width,
multiplier: 0.5,
constant:40))
    
}

override func didReceiveMemoryWarning() {
    super.didReceiveMemoryWarning()
}
}