Problems with user defined constructors in C++ - c++

Question

Im having issues with a class constructors that i define. my .cpp's and .h compile on there own but once i try to use them in a main and construct a class it throws errors.
ive read about how not properly defining a user created constructor may cause the same error but im positive that everything is correct.
joust.cpp
#include "joust.h"
2 //create class construct for knight class
3 //set his name stam and put him on a horse
4 knight::knight (string n) : equipped_wep(5,5,"Basic Blade"){
5 name = n;
6 stamina = 100;
7 mounted = true;
8 }
9
10 void knight::show_stats() {
11 if (stamina) {
12 cout << name << " is not exhausted (stamina="<< stamina<< ") and is moun ted" << endl;
13 } else {
14 cout << name << " has passed out from exhaustion" << endl;
15 }
16 }
17 void knight::show_wep() {
18 cout << name << " is using " << equipped_wep.display_wep() << endl;
19 }
20
21 void knight::equip_weapon(weapon wep) {
22 equipped_wep = wep;
joust.h
13 #ifndef JOUST_H
14 #define JOUST_H
15
16 #include <iostream>
17 #include <fstream>
18 #include <vector>
19
20 using namespace std;
21
22 class weapon {
23 public:
24 weapon(float = 1, float = 1, string = "base");
25 void set(float, float);
26 string display_wep();
27 private:
28 float effectivness;
29 float weight;
30 string name;
31 };
32
33 class knight {
34 public:
35 knight( string = "base");
36 void show_stats();
37 void show_wep();
38 void equip_weapon(weapon wep);
39 private:
40 weapon equipped_wep;
41 string name;
42 int stamina;
43 bool mounted;
44 };
45
46
47 #endif
test.cpp
#include "joust.h"
2
3 int main() {
4 //knight jim("Rob the Third");
5 //jim.show_stats();
6 weapon c(15,12,"jard");
7
8 return 0;
9 }
makefile
test: test.o joust.o
2 g++ -std=c++11 joust.o test.o -o test
3 test.o: test.cpp joust.h
4 g++ -std=c++11 test.cpp
5 joust.o: joust.cpp joust.h
6 g++ -std=c++11 -c joust.cpp
7 clean:
8 rm -f joust.o
It should of just created a weapon object bust instead threw this error
make
g++ -std=c++11 test.cpp
Undefined symbols for architecture x86_64:
"weapon::weapon(float, float, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >)", referenced from:
_main in test-501f47.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [test.o] Error 1

Answer 1

There are two problems that you have:
First you need to build all source file together, or to create object files from each source file that you then link together.
The second error is that you don't define (implement) the weapon constructor anywhere.
The first problem is solved by adding the -c flag when building the source files. The -c flags tells GCC to create object files (the files ending in .o). You have it when building the joust.cpp source file, but seem to have forgotten it for the test.cpp source file.
The second problem should be pretty obvious how to solve: Implement the constructor function.