是否可以在Swift属性上设置观察点? [英] Is it possible to set watchpoints on Swift properties?

问题描述

在Objective-C中，有时我会在LLDB中设置观察点，以让我知道实例变量何时更改.我也可以使用Swift属性来做到这一点吗?

In Objective-C, I would sometimes set watchpoints in LLDB to let me know when instance variables had changed. Can I do this with Swift properties too?

现在，我可以实现的唯一方法是:

Right now, the only way I can achieve this is:

• 在属性中添加didSet处理程序并在其中设置断点(但这需要停止程序并重新编译，这会破坏目的)
• 在[setPropertyName:]上添加符号断点，但这仅在该类恰好支持Objective-C桥接的情况下有效

• adding a didSet handler to the property and setting a breakpoint inside (but this requires stopping the program and recompiling, which kind of defeats the purpose)
• adding a symbolic breakpoint on [setPropertyName:] but this only works if the class happens to support Objective-C bridging

我还有其他选择吗?

推荐答案

答案比我想象的简单得多.最简单的方法是在属性声明上添加一个断点.每当读取或写入属性时，调试器都会中断.

The answer was much simpler than I imagined. The easiest way to do this is to simply add a breakpoint on the property declaration. The debugger will break whenever the property is either read or written.

如果像我一样，您只想在更改属性时中断并且忽略获取，请在属性声明上设置断点，然后进入LLDB控制台并键入"br list"以查看所有断点的列表:

If, like me, you want to break only when the property is changed and ignore fetches, set a breakpoint on the property declaration, then go into the LLDB console and type "br list" to see a list of all your breakpoints:

(lldb) br list
Current breakpoints:
1: file = '/Users/testuser/Desktop/TestFoo/Test.swift', line = 12, locations = 3, resolved = 3, hit count = 1

  1.1: where = TestFoo`TestFoo.Test.x.getter : Swift.Int + 12 at Test.swift:12, address = 0x00000001084cfefc, resolved, hit count = 1 
  1.2: where = TestFoo`TestFoo.Test.x.setter : Swift.Int + 16 at Test.swift:12, address = 0x00000001084cff80, resolved, hit count = 0 
  1.3: where = TestFoo`TestFoo.Test.x.materializeForSet : Swift.Int + 16 at Test.swift:12, address = 0x00000001084d00f0, resolved, hit count = 0 

如您所见，有一个主断点"1"和三个子断点.禁用getter的子断点:

As you can see, there's a master breakpoint "1" with three sub-breakpoints. Disable the sub-breakpoint for the getter:

(lldb) br disable 1.1
1 breakpoints disabled.

您已经准备就绪.仅当修改该属性时，调试器才会中断.

and you're all set. The debugger will break only when that property is modified.

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