如何添加具有约束的子视图以使子视图具有与其父视图相同的框架？

Question

在UIView我有一个方法presentView() ：

public func presentView() {

    UIApplication.sharedApplication().delegate?.window??.addSubview(self)

    let blurEffect = UIBlurEffect(style: .Light)
    let blurEffectView = UIVisualEffectView(effect: blurEffect)
    blurEffectView.backgroundColor = UIColor.yellowColor()
    addSubview(blurEffectView)

    let topConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Top, relatedBy: .Equal, toItem: self, attribute: .Bottom, multiplier: 1, constant: 0)
    let bottomConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Bottom, relatedBy: .Equal, toItem: self, attribute: .Top, multiplier: 1, constant: 0)
    let leadingConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Leading, relatedBy: .Equal, toItem: self, attribute: NSLayoutAttribute.Leading, multiplier: 1, constant: 0)
    let trailingConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Trailing, relatedBy: .Equal, toItem: self, attribute: NSLayoutAttribute.Trailing, multiplier: 1, constant: 0)

    self.addConstraints([topConstraint, bottomConstraint, leadingConstraint, trailingConstraint])

    print("newframe: \(blurEffectView.frame)")

}

但这是错误的，因为这是控制台上的输出：

newframe：（0.0，0.0，0.0，0.0）

结果是：

Answer 1

记住：

blurEffectView.translatesAutoresizingMaskIntoConstraints = false

接着：

let topConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Top, relatedBy: .Equal, toItem: self, attribute: .Top, multiplier: 1, constant: 0)
let bottomConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Bottom, relatedBy: .Equal, toItem: self, attribute: .Bottom, multiplier: 1, constant: 0)
let leadingConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Leading, relatedBy: .Equal, toItem: self, attribute: .Leading, multiplier: 1, constant: 0)
let trailingConstraint = NSLayoutConstraint(item: blurEffectView, attribute: .Trailing, relatedBy: .Equal, toItem: self, attribute: .Trailing, multiplier: 1, constant: 0)

addSubview(blurEffectView)
addConstraints([topConstraint, bottomConstraint, leadingConstraint, trailingConstraint])
layoutIfNeeded()