Common means of modeling: aggregation

polymerization

• explain ： Combination and aggregation , No C++ The grammar requirements of , It is a common means in application .
• demand ：
  Equip the computer with a sound system .

 
Cpu.h

#pragma once
#include <string>
using namespace std;

class Cpu{
    
public:
	Cpu(string brand = "Inter", string model = "i5");
	~Cpu();
private:
	string brand;	// brand 
	string model;	// model 
};

Cpu.cpp

#include "Cpu.h"
#include <iostream>

Cpu::Cpu(string brand, string model){
    
	this->brand = brand;
	this->model = model;
	cout << "Cpu  Start " << endl;
}

Cpu::~Cpu(){
    
	cout << "Cpu  end " << endl;
}

 
 
VoiceBox.h

#pragma once

class VoiceBox{
    
public:
	VoiceBox();
	~VoiceBox();
};

VoiceBox.cpp

#include "VoiceBox.h"
#include <iostream>

VoiceBox::VoiceBox(){
    
	std::cout << " Loudspeaker box   Start " << std::endl;
}

VoiceBox::~VoiceBox(){
    
	std::cout << " Loudspeaker box   end " << std::endl;
}

 
 
Computer.h

#pragma once
#include <string>
#include "Cpu.h"

using namespace std;

// Tell compiler , Yes  VoiceBox  This class 
class VoiceBox;

class Computer{
    
public:
	Computer(string cpuBrand, string cpuModel, int hardDisk = 256, int memory = 8);
	~Computer();
	void addVoiceBox(VoiceBox* box);
private:
	Cpu cpu;		//Cpu
	int hardDisk;	// Hard disk 
	int memory;		// Memory 
	VoiceBox* box;	// Speakers and computers are  " polymerization "  Relationship 
};

Computer.cpp

#include "Computer.h"
#include <iostream>

Computer::Computer(string cpuBrand, string cpuModel, 
	int hardDisk, int memory) : cpu(cpuBrand, cpuModel)
{
    
	// Use pointer mode 
	//this->cpu = new Cpu(cpuBrand, cpuModel);
	this->hardDisk = hardDisk;
	this->memory = memory;
	cout << " Computer   Start " << endl;
}

Computer::~Computer(){
    
	//delete cpu;
	cout << " Computer   end " << endl;
}

void Computer::addVoiceBox(VoiceBox* box){
    
	this->box = box;
}

 
 
main.cpp

#include "Computer.h"
#include "VoiceBox.h"
#include <Windows.h>

using namespace std;

void test(VoiceBox *box) {
    
	Computer computer(" Intel ", "i9 11900k", 512, 32);
	computer.addVoiceBox(box);
}

int main(void) {
    
	VoiceBox box;

	test(&box);

	system("pause");
	return 0;
}

• Aggregation is not a constituent relationship , Contained objects , It may also be contained by other objects .
  The owner , You don't have to be responsible for the life cycle of the object you own .

UML The combination in represents ：