ios - 如何在 VFL 中编写 topLayoutGuide 约束

Question

我正在学习通过代码在 VFL 中编写约束

我已将 View 水平居中，如下所示:

let constraintY = NSLayoutConstraint.constraintsWithVisualFormat(
            "H:[superview]-(<=1)-[collaboratorView]",
            options: NSLayoutFormatOptions.AlignAllCenterY,
            metrics: nil,
            views: ["superview":self.assetsView, "collaboratorView":collaboratorView])

但我想知道如何将约束写入 topLayoutGuide 在 Storyboard中看起来像那样

我最终得到了这样的结果，但它不起作用;(

let bar = NSLayoutConstraint.constraintsWithVisualFormat(
            "V:|[collaboratorView]",
            options: [NSLayoutFormatOptions.AlignAllTop],
            metrics: nil,
            views: ["collaboratorView":self.collaboratorView])

Answer 1

您可以定义如下:

let views : [String : AnyObject] = ["collaboratorView": collaboratorView,
  "topLayoutGuide": topLayoutGuide,
  "bottomLayoutGuide": bottomLayoutGuide]

// 2
var allConstraints = [NSLayoutConstraint]()

// 3
let verticalConstraints = NSLayoutConstraint.constraintsWithVisualFormat(
  "V:[collaboratorView]-12-[topLayoutGuide]",
  options: [],
  metrics: nil,
  views: views)
allConstraints += verticalConstraints