Problem to init class, linker command fail

I try to code my own class like a ball example but I cannot manage to compile my simple code.
In parrallele I mange to compile the example with Particle, so I presume the probleme is not from my system or computer.

main.c

#include "ofMain.h"
#include "ofApp.h"

int main( ){
	ofSetupOpenGL(1024,768,OF_WINDOW);
	ofRunApp(new ofApp());
}

ofApp.cpp

#include "ofApp.h"

void ofApp::setup(){
}

ofApp.h

#pragma once
#include "ofMain.h"
#include "Body.h"

class ofApp : public ofBaseApp{
	public:
		Body mybody;
		void setup();
};

Body.cpp

#include "Body.h"

Body::Body() {
	return;
}

Body.h

#ifndef BODY_H
# define BODY_H

#include "ofMain.h"

class Body {
	public:
		Body();
}; 

#endif

Xcode failled to build and return this error :
05

After few hours to make nothing, I solved the problem and it’s not my code but my missing knowledge with Xcode… I must add the new files .h and .c in the Xcode folder is not automatic :frowning: