24hs-2 面向对象程序设计-优快云博客

本文通过创建一个汽车类实例，详细介绍了C++面向对象编程中的类和对象概念。包括如何定义类、初始化成员变量及实现成员函数。演示了不同情况下汽车属性的输入、显示重量与最高速度的方法。

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面向对象程序设计OOP， Object-oriented Programming, 是使程序设计变得更加简单的一种编程方法。

2.1 理解类

C++使用类描述某种数据类型。类类似于C中的结构，但是不能向结构添加函数。

#include <iostream> using namespace std; class car { public: car(); void printdata(); void printweight(); void printtopspeed(); private: int length; int width; int horsepower; }; car::car() { //Read the length of the car from the keyboard cout << "Define the car's length!" << endl; cin >> this->length; //Read the width of the car from the kayboard cout << "Define the car's width!" << endl; cin >> this->width; //Read the car's horsepower from the keyboard cout << "Define the car's horsepower!" << endl; cin >> this->horsepower; } void car::printdata() { //Print out thar car's data cout << endl << "This is the car's data: " << endl; cout << "Length: " << this->length <<endl; cout << "Width: " << this->width << endl; cout << "Horse power: " << this->horsepower << endl; } void car::printweight() { //Print out the car's weight to the screen: cout << "Weight: " << (this->length * this->width * 100); } void car::printtopspeed() { //Print out the car's top speed to the screen if(this->horsepower <= 200) { cout << endl << "Top speed: " << (this->horsepower * 1.2) <<endl; } if(this->horsepower > 200) { cout << endl << "Top speed: " << (this->horsepower * 0.8) <<endl; } } int main(int argc, char *argv[]) { car a_car; a_car.printdata(); a_car.printweight(); a_car.printtopspeed(); system("PAUSE"); return EXIT_SUCCESS; }

在构造函数中使用动态内存分配方法手动分配内存：注意各个私有变量都定义成指针了，在使用的时候就是*this->length的形式。

#include <iostream> using namespace std; class car { public: car(); ~car(); void printdata(); void printweight(); void printtopspeed(); private: int *length; int *width; int *horsepower; }; car::car() { //Allocate memory dynamically for the data length = new int; width = new int; horsepower = new int; //Read the length of the car from the keyboard cout << "Define the car's length!" << endl; cin >> *this->length; //Read the width of the car from the kayboard cout << "Define the car's width!" << endl; cin >> *this->width; //Read the car's horsepower from the keyboard cout << "Define the car's horsepower!" << endl; cin >> *this->horsepower; } car::~car() { //This function will be called when to object is finished. //We free up memory with the delete keyboard. delete length; delete width; delete horsepower; } void car::printdata() { //Print out thar car's data cout << endl << "This is the car's data: " << endl; cout << "Length: " << *this->length <<endl; cout << "Width: " << *this->width << endl; cout << "Horse power: " << *this->horsepower << endl; } void car::printweight() { //Print out the car's weight to the screen: cout << "Weight: " << ((*this->length) * (*this->width) * 100); } void car::printtopspeed() { //Print out the car's top speed to the screen if(*this->horsepower <= 200) { cout << endl << "Top speed: " << ((*this->horsepower) * 1.2) <<endl; } if(*this->horsepower > 200) { cout << endl << "Top speed: " << ((*this->horsepower) * 0.8) <<endl; } } int main(int argc, char *argv[]) { car a_car; a_car.printdata(); a_car.printweight(); a_car.printtopspeed(); system("PAUSE"); return EXIT_SUCCESS; }