Undefined symbols for architecture x86_64 error on xcode

Question

I have a simple project, on my basic ViewController.m i'm trying to move to another UIViewController by doing:

@implementation ViewController

- (void)viewDidLoad {
[super viewDidLoad];
...
}

- (void)addAlarmBrick {
NewAlarmViewController *navc = [[NewAlarmViewController alloc] init];
[self presentViewController:navc animated:YES completion:nil];
}

I have the NewAlarmViewController on my project with the .m file listed in the target membership.

This is the full error message:

Undefined symbols for architecture x86_64:
"_OBJC_CLASS_$_NewAlarmViewController", referenced from:
 objc-class-ref in ViewController.o ld: symbol(s) not found for architecture x86_64
 clang: error: linker command failed with exit code 1 (use -v to see invocation)

what am i doing wrong over here?

EDIT:

Adding the settings for both files:

.m file:

.h file:

Answer 1

Well, It turns out the error was not adding the following to the relevant file:

@implementation NewAlarmViewController


@end

I don't know why the @implementation must be added, but it must be.

Answer 2

Maybe Xcode messed sth up. Did you already try removing NewAlarmViewController from the project and readding it again? -> Select .h and .m file, press delete, remove reference, and then drag them again into your project.

Also clean the build folder (cmd + alt + shift + k) and rebuild your project.

Answer 3

It sounds like you might have a library included in your project that is only compiled for ARM, and doesn't provide object code to run on the simulator. Did you include any third party libraries in your project? (Or is NewAlarmViewController from a third party library?)

Answer 4

Go to All settings, select your project and check for Architecture and compiler for c/c++/obj c under build options as shown in the screenshot.