如何创建简单的OOP程序(分开主程序和头文件)

今天药忘吃喽~ 2022-08-06 07:12 90阅读 0赞

参考链接：[https://www3.ntu.edu.sg/home/ehchua/programming/cpp/cp3\_OOP.html][https_www3.ntu.edu.sg_home_ehchua_programming_cpp_cp3_OOP.html] 很适合C++新手创建OOP工程的一些例子和指导

我的编译环境： VS 2010

举一个例子：创建一个书的类和作者的类，每个类中包含相关成员变量和成员函数。具体有什么成员函数和变量，以下程序一看便知：

首先是头文件 - Author.h：

/* Header for the Author class (Author.h) */
    #ifndef AUTHOR_H
    #define AUTHOR_H
    
    #include <string>
    using namespace std;
    
    class Author
    {
    private:
    	string name;
    	string email;
    	char gender;
    public:
    	Author(string name, string email, char gender);
    	string getName() const;
    	string getEmail() const;
    	void setEmail(string email);
    	char getGendar() const;
    	void print() const;
    };
    
    #endif

然后创建 Author.cpp 实现各个成员函数：

#include <iostream>
    #include "Author.h"
    
    //using namespace std;	//可以省略，因为Author.h中包含了
    
    Author::Author(string name, string email, char gender)
    {
    	this->name = name;
    	setEmail(email);	// Call setter to check for valid email
    	if(gender == 'm' || gender == 'f')
    	{
    		this->gender = gender;
    	}
    	else
    	{
    		cout << "invalid gender! set to 'u'(unknown)" << endl;
    		this->gender = 'u';
    	}
    }
    
    string Author::getName() const
    {
    	return name;
    }
    
    string Author::getEmail() const
    {
    	return email;
    }
    
    void Author::setEmail(string email)
    {
    	// Check for valid email. Assume that a valid email contains
    	//  a '@' that is not the first nor last character.
    	size_t atIndex = email.find('@');
    	if(atIndex != string::npos && atIndex != 0 && atIndex != email.length() - 1)
    	{
    		this->email = email;
    	}
    	else
    	{
    		cout << "invalid email! set to empty string!" << endl;
    		this->email = "	";
    	}
    }
    
    char Author::getGendar() const
    {
    	return gender;
    }
    
    void Author::print() const
    {
    	cout << name << "(" << gender << ")" << email << endl;
    }

最后编写测试文件 test.cpp：

#include <iostream>
    #include "Author.h"
    
    //using namespace std;	//可以省略，因为Author.h中包含了
    
    int main()
    {
    	Author peter("Peter Jones","peter@somewhere.com",'m');
    	peter.print();
    	peter.setEmail("peter@xyz.com");
    	peter.print();
    	Author paul("Paul Jones","@somewhere.com",'n');
    	paul.setEmail("paul@");
    	paul.print();
    	cout << "Sucessfully!" << endl;
    
    	return 1;
    }

假设一本书只被一个作者编写，我们可以用类对象定义Book类的成员变量：

编写 Book.h ：

/* Header for the class Book (Book.h) */
    #ifndef BOOK_H
    #define BOOK_H
    
    #include <string>
    #include "Author.h"
    
    class Book
    {
    private:
    	string name;
    	Author author;
    	double price;
    	int qtyInStock;
    public:
    	Book(string name, Author author, double price, int qtyInStock = 0);
    	string getName() const;
    	Author getAuthor() const;	// Returns an instance of the class Author
    	double getPrice() const;
    	void setPrice(double price);
    	int getQtyInStock() const;
    	void setQtyInStock(int qtyInStock);
    	void print() const;
    	string getAuthorName() const;
    };
    
    #endif

再实现Book类的方法Book.cpp：

#include <iostream>
    #include "Book.h"
    
    Book::Book(string name, Author author, double price, int qtyInStock)
    	:name(name), author(author)
    {
    	setPrice(price);
    	setQtyInStock(qtyInStock);
    }
    
    string Book::getName() const
    {
    	return name;
    }
    
    double Book::getPrice() const
    {
    	return price;
    }
    
    Author Book::getAuthor() const
    {
    	return author;
    }
    
    void Book::setPrice(double price)
    {
    	if(price > 0)
    	{
    		this->price = price;
    	}
    	else
    	{
    		cout << "price should be positive! set to 0." << endl;
    		this->price = 0;
    	}
    }
    
    int Book::getQtyInStock() const
    {
    	return qtyInStock;
    }
    
    void Book::setQtyInStock(int qtyInStock)
    {
    	if(qtyInStock > 0)
    	{
    		this->qtyInStock = qtyInStock;
    	}
    	else
    	{
    		cout << "qtyInStock cannot be negative! Set to 0." << endl;
    		this->qtyInStock = 0;
    	}
    }
    
    void Book::print() const
    {
    	cout << "'" << name << "'by";
    	author.print();
    }
    
    // Return the author' name for this Book
    string Book::getAuthorName() const
    {
    	return author.getName();	// invoke the getName() on instance author
    }

最后进行测试。把下面的test.cpp换成上面的test.cpp，并且把Book.h和Book.cpp文件添加到原Author工程中，就可以了：

#include <iostream>
    #include "Book.h"
    
    int main()
    {
    	Author peter("Peter Jones","peter@somewhere.com",'m');
    	peter.print();
    
    	Book cppDummy("C++ for Dummies",peter,19.99);
    	cppDummy.setQtyInStock(88);
    
    	cout << cppDummy.getQtyInStock() << endl;
    	cout << cppDummy.getPrice() << endl;
    	cout << cppDummy.getAuthor().getName() << endl;
    	cout << cppDummy.getAuthor().getEmail() << endl;
    	cout << cppDummy.getAuthor().getGendar() << endl;
    	cout << cppDummy.getAuthorName() << endl;
    
    	Book moreCpp("More C++ for Dummies",peter,-199);
    	cout << moreCpp.getPrice() << endl;
    
    	return 1;
    }

虽然程序很简单，但是的确能帮助我很好的理解OOP编程。这也是C++最大的特色之一，勤加练习，我相信一定能有所成就。

[https_www3.ntu.edu.sg_home_ehchua_programming_cpp_cp3_OOP.html]: https://www3.ntu.edu.sg/home/ehchua/programming/cpp/cp3_OOP.html