c++类中如何对函数进行获取和更改

类中
set函数
和
get函数
的结合如何使数据进行查看和更改，请大致写出思路，谢谢帮助
#include
using namespace std;
class Box
{
public:

Box(float = 1, float = 1, float = 1);

virtual ~Box();

void Show();

private:
float length, width, height;
};

#include "Box.h"
using namespace std;

/*
Box::Box()
{
length = 1; width = 1; height = 1;
cout << "Box("<<length<<","<<width<<","<<height<<")";
cout << "is constructed!" << endl;
}

*/

Box::Box(float L,float W,float H)
{
length = L; width = W; height = H;
cout << "Box(" << length << "," << width << "," << height << ")";
cout << "is constructed!" << endl;
}

void Box::Show()
{
cout << "length:" << length << endl;
cout << "width:" << width << endl;
cout << "height:" << height << endl;
cout <<"tiji" << length*width*height << endl;
cout << "mianji" << (2*((length*width)+(width*height)+(length*height))) << endl;
}

Box::~Box()
{
cout << "Box(" << length << "," << width << "," << height << ")";
cout << "is constructed!" << endl;
}

#include
#include "Box.h"
using namespace std;

int main()
{
Box box1;
box1.Show();
box1.~Box();

Box box2(4,2,3);
box2.Show();


system("pause");

}

float Box::getLength(){
    return length;
}

float Box::getHeight(){
    return height;
}

float Box::getWidth(){
    return width;
}

void Box::setLength(float length){
    this->length = length;;
}

void Box::setHeight(float height){
    this->length = height;
}

void Box::setWidth(float width){
    this->length = width;
}

void Box::set(float length = 1, float width = 1, float height = 1){
    this->length = length;
    this->width = width;
    this->height = height;
}

这样应该没问题了

float Box::getLength(){
    return this->length;
}

float Box::getHeight(){
    return this->height;
}

float Box::getWidth(){
    return this->width;
}

void Box::setLength(float length){
    this->length = length;;
}

void Box::setHeight(float height){
    this->length = height;
}

void Box::setWidth(float width){
    this->length = width;
}

void Box::set(float length, float width, float height){
    this->length = length;
    this->width = width;
    this->height = height;
}

不好意思，一时粗心

float Box::getLength(){
    return this->length;
}

float Box::getHeight(){
    return this->height;
}

float Box::getWidth(){
    return this->width;
}

void Box::setLength(float length){
    this->length = length;;
}

void Box::setHeight(float height){
    this->height = height;
}

void Box::setWidth(float width){
    this->width = width;
}

void Box::set(float length, float width, float height){
    this->length = length;
    this->width = width;
    this->height = height;
}