the breakpoint will always be skipped. Your breakpoint condition can be any code that evaluates true or false. For example, if you only want the breakpoint to stop when running on the main thread, you could use[NSThread isMainThread] as your condition.
使用[NSThread isMainThread]可以判断是否运行在主进程。
可以不接触源码的情况下断点函数：
Symbolic Breakpoints
Symbolic breakpoints allow you to set breakpoints whenever specific selectors are sent messages. For example, here’s thesymbolicBreakpointAction: method in the demo app:
观察变量什么时候被修改
(lldb) watch set variable _button1ClickCount
Watchpoint created: Watchpoint 1: addr = 0x0b9a1ca4 size = 4 state = enabled type = w
declare @ 'MyStuff/MyStuff/BNRDetailViewController.m:52'
watchpoint spec = '_button1ClickCount'
new value: 10