Unrecognized selector sent to instance positioning

There are many reasons for unrecognized selector sent to instance, the method of the object being pre-release, the referenced instance does not exist, or the method is not implemented in the class, and so on. The console is simply a matter of telling you that this error occurred, followed by a heap of stack-related addresses.

At this time to quickly locate the bug, custom debug breakpoint is a better approach, because the better I have not thought of.

OK, the nonsense is less, the steps are as follows:
1. After selecting Debug->breakpoints->create symbolic Breakpoint Click on the menu bar of Xcode, a breakpoint is added and the edit box will pop up.

2. Fill in the symbol in the edit box -[nsobject(nsobject) doesnotrecognizeselector:] This method is signed, For the students who look at the Ben Boven side of the test, after copying the method signature to paste the time, found that the edit box in Xcode is missing, right click on the breakpoint just added, select Edit Breakpoint can.

3. Run the code and the breakpoint will stay where it caused the crash.

Unrecognized selector sent to instance positioning