main.cpp

#include <cstdio>
#include "other.h"

int main() {
    Foo f = Foo::Make(1);
    f.print_me();

    return 0;
}

other.cpp

#include "other.h"
#include <cstdio>

Foo Foo::Make(int v) {
    return { v };
}

void Foo::print_me() {
    printf("Hello, I'm #%d\n", val);
}

other.h

struct Foo {
    static Foo Make(int);
    void print_me();
    int val;
};