This happens when Xcode’s indexing process fails for some reason. This can be a header file is missing to code highlighting (which can be different from the compiler in some cases) or in some cases a bad #define. The problem is that it fails silently so you cannot fix it.

After having this problem with a big project I stumbled onto the magic hint on Stack Overflow.  After you quit Xcode enter this into a shell:

defaults write com.apple.dt.Xcode IDEIndexingClangInvocationLogLevel 3

After this you should open the project and see messages like this:

Xcode: IDEIndexingClangInvocation: Failed to save PCH file: /Users/user/Library/Developer/Xcode/DerivedData/Project-drsrrgaenperjadmqslqfxyqcqyt/Index/PrecompiledHeaders/Some-Prefix-cgepzuvkwimbsvcmqrbbpeoyhdpz_ast/Some-Prefix.pch.pth

Looking through these messages will show you what goes on and might help you finding the problem.

For me it was just copying header files from a framework on the place the Clang parser was looking for them.

Here’s a little script you can run, that enables the remote Web Inspector via gdb (via @atnan).

Here’s to all the mobile devs!

Here’s how it’s done. In your Application Delegate add the following code:

+ (void)initialize;
{
    [NSClassFromString(@"WebView") performSelector:@selector(_enableRemoteInspector)];
}

With this you can direct your browser to http://localhost:9999 to open the web inspector.

Have fun!

You can symbolicate individual addresses from the crashlog in the terminal using a command named `atos` (if you’ve got the dSYM file for your build). Here’s an example:

atos -arch armv7 -o MyApp.app.dSYM/Contents/Resources/DWARF/MyApp 0x0000babe

This will output you the line of code related to this address. I.e.:

+[MyHappyClass fullOfFail] (in MyApp) + 429

Pro Tip: not entering the address when calling the atos command leaves you in STDIN mode. Here you can add multiple addresses without restarting the tool.

ssh [name of your mac].[mobile me username].members.mac.com

If you have a dot in your username you can escape it by prefixnig it with \\. So if your hostname would be Mainbrain and your mobileMe username is jon.doe the terminal command would look as following:

ssh mainbrain.jon\\.doe.members.mac.com

• In the Hardware menu, enable “Simulate Hardware Keyboard”.
• Hit the shift key three times in a row

Now all the animations are slowed down for debugging. Triple-hit Shift again to deactivate.

Here’s the story (you may skip this part): The issue was, that we added a method -setParameters: to NSMutableURLRequest which takes a dictionary and set’s it as query string or multipart form body depending on the HTTP Method used for sending the request. This method sadly conflicted with a category on the same class defined in a library called OAuthConsumer which doesn’t take a dictionary as argument but rather an array of key-value pairs. Both categories we’re linked to our application as static libraries.

The result was that our -setParameters: was called with an array although a dictionary was expected. We noticed the problem since NSArray is not responding to -allKeys. It could have gone would have not noticed the problem. Just imagine trying to debug a misbehavior when you’re looking at the wrong piece of code.

The quintessence, and what basically helped us finding the issue is a environment variable named OBJC_PRINT_REPLACED_METHODS. Similar to NSZombieEnabled you set it in the Arguments tab of your executable info as variable set to environment. Just like this:

fb -[_NSZombie init]
fb -[_NSZombie retainCount]
fb -[_NSZombie retain]
fb -[_NSZombie release]
fb -[_NSZombie autorelease]
fb -[_NSZombie methodSignatureForSelector:]
fb -[_NSZombie respondsToSelector:]
fb -[_NSZombie forwardInvocation:]
fb -[_NSZombie class]
fb -[_NSZombie dealloc]

But you should also know that this only works on NS classes. To have a similar effect on CoreFoundation classes use CFZombieLevel. The value of CFZombieLevel is defined by a bit array. See the following table. A good value is 5

Bit	Action
0	scribble deallocated CF memory
1	when scribbling deallocated CF memory, don't scribble object header (CFRuntimeBase)
4	never free memory used to hold CF objects
7	if set, scribble deallocations using bits 8..15, otherwise use 0xFC
8..15	if bit 7 is set, scribble deallocations using this value
16	scribble allocated CF memory
23	if set, scribble allocations using bits 24..31, otherwise use 0xCF
24..31	if bit 16 is set, scribble allocations using this value

• The framework needs to have @executable_path/../Frameworks as Installation Directory in it’s build settings.
• The app should include the following in its framework search path: “$(CONFIGURATION_BUILD_DIR)/$(CONTENTS_FOLDER_PATH)/Frameworks” (including the quotes!)
• Also make sure to have a Copy Frameworks build phase and that your famework is added to it.