Xcode “Use of undeclared identifier” errors, compi

问题:

I've got an incredibly annoying issue that is hampering my workflow. In my project I have "User of undeclared identifier" errors all over. They are all in reference to a single class, specifically a Theme class. I checked for any circular referencing with my imports, none. I'm really confused.

Here is a screenshot of the errors. I would post errors in the Build Log for more detail, but there aren't any. It builds and runs just fine...

I've tried cleaning, deleting the derived data... Any ideas?

回答1:

I was having the same problem and noticed that all of the undeclared identifiers were declared in files that were in my pch file.

With this in mind I deleted one of the #import lines from the pch file and recompiled which failed as expected. I then put the deleted line back in, recompiled and it compiled normally with all the false errors gone.

Hopefully this simple solution helps a few of you out if the above solutions don't.

回答2:

These kinds of errors are quite common with Xcode, unfortunately. It would be great if it would auto-refresh its error list all the time, but it doesn't always. When this happens, I strongly suggest that you restart Xcode, which will flush its error cache and hopefully solve your issues.

回答3:

How are you including this class? In most cases I just include the class explicitly in header and/or body - instead of the *.pch file. Then this error goes away in my case.

Also deleting the derived data workes once in a while. Did you change the location in preferences recently by any chance. I also got this error when I use a ramdisk for derived data and then go back to default. This is the most annoying case - since it causes this error to appear then in almost every file.

This error seems to happen more often in Xcode 4.4 than the prior versions.

回答4:

Have you included the library files correctly? Take a look at that. Sometimes ARC issues might occur if we don't include the correct file, or something's missing or not connecting UI.

回答5:

For me the issue was that I created UnityInterface.h/m file to handle the obj-c to c# interface. UnityInterface.h is already defined by Unity. I renamed my own UnityInterface to _UnityInterface and now everything works.

回答6:

Just posting this for anyone who might have this problem later and doesn't find any of these solutions to work: If you have any pragma marked #if statements that only execute if the program is in debug mode it will obviously cause anything declared inside of them to not be declared when you try to archive/export.

回答7:

I had the same problem. Closing and opening XCode didn't help.

I solved it by checking errors in other targets and fixing them (I had tons of errors in my unit testing target). Also I moved header links from h files to m files. But I'm pretty sure, that the first thing was critical.

回答8:

For others who experienced the same problem and tried all solution above with no result, perhaps you should try something like I did. I solved the problem simply by unplugging my iPhone USB cable from my Mac and then replugged again those cable. After that, rebuilt again and all undeclared identifier errors were gone.

回答9:

I had the same error. In my case, it was on this line of code:

- (void)playerItemDidReachEnd:(NSNotification *)notification {
      // some code
  }

My error message said:

Use of undeclared identifier 'playerItemDidReachEnd'

I tried added this line to the .h file:

- (void)playerItemDidReachEnd:(NSNotification *)notification;

I cleaned it, I re-booted my macbook, and I was still getting the error.

Finally, I decided to try to delete the line in the .h file. I then pasted it into a text file, and then copied and pasted it back in to the .h file.

Now I cleaned and VOILA' !!! no more errors. Go figure. This happens sometimes in VBA. Somehow there seems to be unseen formatting in a line of code. So I thought it might be happening with xCode. Cutting it out, pasting into a text file, cutting out of the text file, and pasting it back in right where it was - fixed it in my case.

---- UPDATE ----- The above was posted as my answer. Apologies, apparently there's something else wrong.

After cleaning - my ERRORS were gone. Now I tried to build and run my app. THE ERRORS CAME BACK! So this time I re-created the class files after cutting out all the text, and pasting it into a text file. I did it for both my .m and .h files. But now the errors are back again after trying to run. SORRY. I don't know how to delete this text altogether cuz it is not an answer.

Tried to build and run my app. THE ERRORS CAME BACK!

There was also an error msg that I was missing a bracket ( } ). Finally I looking at the method just before this method, and sure enought it was missing the ending bracket! That was it!

回答10:

Might be little late in answering.

I had this issue very recently. I fix this by updating my OS and then updating Xcode. I tried updating Xcode alone but did not happen because Xcode 9.4 requires OS High Sierra 10.13.*

Happy Updating :)