objective-c - Xcode5 如何调试快速定位出错行

Question

、、、objectivec 2014-07-21 18:02:38.259 Sections[2962:70b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'must pass a class of kind UITableViewCell' *** First...

PHP中文网 · Answer

Add an exception breakpoint (Add Exception Breakpoint) in Xcode's Breakpoint Navigator, and then set the breakpoint condition to Exception: Object-C, so that it can break before the exception is thrown, and you can view the call stack at that time.

Note that it is best to turn on this breakpoint when the problematic code is about to be executed, otherwise it will continue to be disturbed by various exceptions.

PHP中文网 · Answer

Your project is called Sections, right?
This is where your exception is thrown:
4 Sections 0x000030eb -[BIDViewController searchDisplayController:didLoadSearchResultsTableView:] + 171
The code offset of the searchDisplayController method of the BIDViewController class is 171 (almost the 170 characters of this method, almost lines 2 and 3. Remember, 171 is not a line number or something).

About iOS exception analysis, it is really a headache at the beginning, because it does not directly tell the developer where the exception is thrown, and sometimes there is even no exception stack. Even if there is an exception stack, it is not easy to understand what it means. In particular, the code offset number is extremely misleading. There are usually many debugging methods, and it would take an entire night to cover them all. The Exception breakpoint answered by Huan Du is one, and of course there is also the log assertion print viewing method, symbolic breakpoint setting, and LLDB debugging tool. Personally, I still prefer the stack analysis method posted in your question. Basically, the problem can be determined based on the class name, method name and code offset.

Regarding the stack report, briefly introduce the meaning of its content:
For example:
4 Sections 0x000030eb -[BIDViewController searchDisplayController:didLoadSearchResultsTableView:] + 171
It includes a total of 5 parts: 4/Sections/0x000030eb/-[BIDView...ew:]/171
Part 1: The stack outputs the sequence number. The larger the sequence number, the earlier the code is called;
Part 2: The framework (library/project) to which the called method belongs. For example, Sections is your project;
Part 3: The memory address of the calling method, which is 0x000030eb
Part 4: Calling method name, this is very important, that is - [BIDViewController searchDisplayController:didLoadSearchResultsTableView:]
Part 5: The code offset after calling the method after compilation. Here again, it is not the line number, but the compiled code offset, but it is basically the same as the number of characters. You can use some text tools to count your methods. The character offset is a rough estimate of the wrong line, and the general error is within 3 to 5 lines.

Here is a little tip to prevent xcode from not printing stack logs:
Add @try@catch on the main method in main.m, like this:

#import 

#import "AppDelegate.h"

int main(int argc, char* argv[])
{
    @try {
        @autoreleasepool
        {
            return UIApplicationMain(argc, argv, nil, NSStringFromClass([AppDelegate class]));
        }
    }
    @catch (NSException* exception)
    {
        Log(@"Exception=%@
Stack Trace:%@", exception, [exception callStackSymbols]);
    }
}

But remember to delete the try catch package before publishing the app, dear~~~

大家讲道理 · Answer

[UITableView registerClass:forCellReuseIdentifier:] Something went wrong here!