How to load dylib or .a (static library) file using objective-C?

First off, this has precisely nothing to do with Xcode.

Now, you can't load static libraries dynamically, because a static library is just a collection of object files, which are not, by themselves, executable.

In order to load a dynamic library, use the dlopen() API:

void *handle = dlopen("/path/to/library.dylib", RTLD_LAZY);

To get a C function pointer:

int (*computeAnswer)(void) = dlsym(handle, "ComputeAnswer");
int answer = computeAnswer(); // 42

To get a C++ function pointer without extern "C" linkage (mangled name):

int (*mangledFunction)(void) = dlsym(handle, "i$mangledFunction_@v");

You can even hack yourself through the Objective-C naming convention of the linker compiler:

@class MyShinyClass;
Class cls = dlsym(handle, "OBJC_CLASS_$_MyShinyClass");

MyShinyClass *instance = [[cls alloc] init];

When you're done with the library, dispose of it:

dlclose(handle);