如上圖，是一個十分簡單的佈局。 root view 上加了一個 button 和一個 webview。

不加識別符號的樣子

1. 檢視層級中沒有標識
   
   只有 UIView、WKWebView 之類，如果view很多，就很難分得清。

2. 約束沒有識別符號 

   只知道 uiview 和uibutton 中心對齊，不知道哪個view 和哪個 button。

3. autoLayout 日誌中沒有識別符號

   (lldb) po [0x7f8aaa50e6d0 _autolayoutTrace]
   
   •UIWindow:0x7f8aaa60a1b0
   |   •UIView:0x7f8aaa502c30
   |   |   *_UILayoutGuide:0x7f8aaa50d140
   |   |   *_UILayoutGuide:0x7f8aaa50d750
   |   |   *UIButton:0x7f8aaa50e6d0'click to send'
   |   |   |   UIButtonLabel:0x7f8aaa6073b0'click to send'
   |   |   *WKWebView:0x7f8aaa851000
   |   |   |   WKScrollView:0x7f8aaa853a00
   |   |   |   |   WKContentView:0x7f8aaa83c400
   |   |   |   |   |   UIView:0x7f8aaa706350
   |   |   |   |   |   |   UIView:0x7f8aaa7002e0
   |   |   |   |   |   |   |   WKCompositingView:0x7f8aaa712200
   |   |   |   |   |   |   |   |   WKCompositingView:0x7f8aaa60ec10
   |   |   |   |   |   |   |   |   |   WKCompositingView:0x7f8aaa60edf0
   |   |   |   |   |   |   |   |   |   |   WKCompositingView:0x7f8aaa60f1b0
   |   |   |   |   |   |   |   |   |   |   |   WKCompositingView:0x7f8aaa60efd0
   |   |   |   |   |   |   |   |   |   |   WKCompositingView:0x7f8aaa60e850
   |   |   |   |   |   |   |   |   |   WKCompositingView:0x7f8aaa60e670
   |   |   |   |   |   |   |   |   WKCompositingView:0x7f8aaa60ea30
   |   |   |   |   UIView:0x7f8aaa7066b0
   |   |   |   |   UIImageView:0x7f8aaa70ce00
   |   |   |   |   UIImageView:0x7f8aaa70cbd0
   
   Legend:
       * - is laid out with auto layout
       + - is laid out manually, but is represented in the layout engine because translatesAutoresizingMaskIntoConstraints = YES
       • - layout engine host
   
   (lldb) po [0x7f8aaa50e6d0 constraintsAffectingLayoutForAxis:0]
   <__NSArrayI 0x600000f3aa30>(
   <NSContentSizeLayoutConstraint:0x6000025ac2a0 UIButton:0x7f8aaa50e6d0'click to send'.width == 102 Hug:250 CompressionResistance:750   (active)>,
   <SnapKit.LayoutConstraint:
    
   [email protected]#26 UIButton:0x7f8aaa50e6d0.centerX == UIView:0x7f8aaa502c30.centerX>,
   <NSLayoutConstraint:0x600002289270 'UIView-Encapsulated-Layout-Width' UIView:0x7f8aaa502c30.width == 375   (active)>
   

   )

為約束增加識別符號

    button.snp.makeConstraints { (make) in
        make.centerX.equalToSuperview().labeled("mybutton centerX")
        make.top.equalToSuperview().offset(50).labeled("mybutton top")
    }

    webView.snp.makeConstraints({ (make) in
        make.leading.trailing.bottom.equalToSuperview().labeled("mywebview Edges")
        make.top.equalToSuperview().offset(200).labeled("mywebview Top")
    })
 

效果

檢視層級中，可以看到約束的識別符號了。 

選中約束之後，可以看到 Identifier了



layout日誌中，可以看到識別符號了 

為 view 設定 accessibilityIdentifier 屬性

view.accessibilityIdentifier = "rootView abi"
button.accessibilityIdentifier = "mybtn abi"
webView.accessibilityIdentifier = "mywebview abi"

效果

layout 日誌中可以看到 



但是 snapKit 約束的描述，設定的accessibilityIdentifier

增加 accessibilityLabel



在檢視層級中，可以看到

總結

• 設定約束的識別符號，無論是 SnapKit，還是系統原生的
• 設定 accessibilityIdentifier 屬性，在日誌中可以幫助定位問題
• 設定 accessibilityLabel 屬性，幫助檢視檢視成績