Question

Actually I build and compile my project with no problem one month age, but today I open my project and go ahead modifying something, I find there is a problem and I don’t know why!

It looks like this.

I have a class(viewController.h/viewController.m)

in viewController.h, I declare two methods

-(void) a;

-(void) b;

in viewController.m, I implement them

-(void) a
{... b()\\invoke method b; ...}

-(void) b
{...\\do something}

but when I build the project, errors occur:

Undefined symbols for architecture i386: “_b”, referenced from:
-[ViewController a] in ViewController.o
(maybe you meant: dyld_stub_binding_helper) ld: symbol(s) not found for architecture i386 clang: error: linker command failed with
exit code 1 (use -v to see invocation)

How can I fix it?

Answer 1

Either use C functions:

viewController.h:

void a();
void b();

viewController.m:

void a() {
    b();
}
void b() {
    // do something
}

or, you can use Objective-C methods:

viewController.h:

- (void)a;
- (void)b;

viewController.m:

- (void)a {
    [self b];
}
- (void)b {
    // do something
}