AutoLayout - VFL

 
        self.view.backgroundColor = UIColor.greenColor()
    
        let superView = UIView(frame: CGRect(x: 20, y: 100, width: 300, height: 400))
        superView.backgroundColor = UIColor.blueColor()
        self.view.addSubview(superView)
        
        let label_01 = UILabel()
        label_01.text = "label_01"
        label_01.backgroundColor = UIColor.redColor()
        superView.addSubview(label_01)
        
        let label_02 = UILabel()
        label_02.text = "label_02"
        label_02.backgroundColor = UIColor.grayColor()
        superView.addSubview(label_02)
        
        let label_03 = UILabel()
        label_03.text = "label_03"
        label_03.backgroundColor = UIColor.brownColor()
        superView.addSubview(label_03)
        
        let label_04 = UILabel()
        label_04.text = "label_04"
        label_04.backgroundColor = UIColor.cyanColor()
        superView.addSubview(label_04)

        
        label_01.translatesAutoresizingMaskIntoConstraints = false
        label_02.translatesAutoresizingMaskIntoConstraints = false
        label_03.translatesAutoresizingMaskIntoConstraints = false
        label_04.translatesAutoresizingMaskIntoConstraints = false

        
        //当屏宽大于两个按钮的宽度时，两个按钮的间隔的优先级会降低；
        //使用AlignAllLeft会提示Options mask required views to be aligned on a horizontal edge, which is not allowed for layout that is also horizontal.； 也就是说当我写水平方向时的布局时，其实只能使用水平相关的NSLayoutFormatOptions限定，否则会因为VFL语句解析出错；
        //设置了左右边距、间隔与宽度；则左右边距和宽度优先；
        let hVFL = "H:|-10-[label_01(60)]-40-[label_02]-30-|"
        let hCons = NSLayoutConstraint.constraintsWithVisualFormat(hVFL, options: NSLayoutFormatOptions.AlignAllTop, metrics: nil, views: ["label_01":label_01, "label_02":label_02])
        superView.addConstraints(hCons)
        
        let vVFL1 = "V:|-80-[label_01]"
        let vCons1 = NSLayoutConstraint.constraintsWithVisualFormat(vVFL1, options: NSLayoutFormatOptions.AlignAllTop, metrics: nil, views: ["label_01":label_01, "label_02":label_02])
        superView.addConstraints(vCons1)
        


        
        
        
        //水平方向如果指定了上边距与下边距 和高度  则以上边距和高度为优先；
        //水平方向只是简单居中
        let hVFL2 = "H:|-[label_03]-|"
        let hCons2 = NSLayoutConstraint.constraintsWithVisualFormat(hVFL2, options: NSLayoutFormatOptions.AlignAllCenterX, metrics: nil, views: ["label_03":label_03])
        superView.addConstraints(hCons2)
        
        
        let hVFL3 = "H:|-[label_04(==label_03)]-|"
        let hCons3 = NSLayoutConstraint.constraintsWithVisualFormat(hVFL3, options: NSLayoutFormatOptions.AlignAllCenterX, metrics: nil, views: ["label_03":label_03, "label_04":label_04])
        superView.addConstraints(hCons3)

        
        let vVFL3 = "V:|[label_03(>=60@900)]-50-[label_04(>=400@899)]-30@901-|"
        let vCons3 = NSLayoutConstraint.constraintsWithVisualFormat(vVFL3, options: NSLayoutFormatOptions.AlignAllLeft, metrics: nil, views: ["label_03":label_03, "label_04":label_04])
        superView.addConstraints(vCons3)