Notes

Debug

控制台打印视图层级结构

po [<view> recursiveDescription]

Not able to use debug view hierachy

• 问题

  UITextView 无法在视图 Debug 中显示

    Assertion failure in -[UITextView _firstBaselineOffsetFromTop]
  

• Solution

  • Link

    // It is an issue of UITextView.
    // Add a category of UITextView and add the lines below to the .m file.
    // Only import when debug mode.
  	
    - (void)_firstBaselineOffsetFromTop {
    }
  
    - (void)_baselineOffsetFromBottom {
    }
  
  

添加 Autolayout Breakpoints

问题

当视图的约束出现错误的时候，控制台在出错约束的最后会提示

Make a symbolic breakpoint at UIViewAlertForUnsatisfiableConstraints to catch this in the debugger.
The methods in the UIConstraintBasedLayoutDebugging category on UIView listed in <UIKit/UIView.h> may also be helpful.

---

添加 Autolayout 断点的方法

1. 按下 ⌘ + 7，转到 Show the Breakpoint navigator

2. 右下角添加 Symbolic Breakpoint…

   

3. 在弹出的对话框中填入配置

   Action 的 Debugger Command

   • 对于 Swift 项目，填入 expr -l objc++ -O -- [[UIWindow keyWindow] _autolayoutTrace]
   • 对于 Objective-C 项目，填入 po [[UIWindow keyWindow] _autolayoutTrace]

   

4. 在运行时，当遇到有异常的约束时，会自动停下，并可以实时改变控件的属性，如

    (lldb) expr ((UIView *)0x7f9ea3d43410).backgroundColor = [UIColor redColor]