对象数组打印空白字符串
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【中文标题】对象数组打印空白字符串【英文标题】:Array of objects prints blank string 【发布时间】:2020-05-14 11:53:04 【问题描述】:(问题已解决,解决方案已作为注释行添加到 main.cpp)
main.cpp 文件中描述了我遇到的问题。我已经检查了有关此的其他问题,但没有一个真正有帮助。
我正在尝试使用 C++ 创建一个控制台应用程序,您可以在其中将 BOOKS 添加到 LIBRARY。在 library 类中,有一个 displayInfo() 函数可以显示特定书籍的信息。它可以显示整数或双值信息而不会出现问题,但是当我尝试显示字符串类型的信息时它会出现问题。它只是打印空白。让我给你一些我的代码示例。
这是 Book.h
#ifndef BOOK_H
#define BOOK_H
#include <string>
class Book
friend class Library;
public:
void setName();
std::string getName();
private:
std::string nameOfBook;
;
#endif
Book.cpp
#include "Book.h"
#include <iostream>
#include <string>
using namespace std;
void Book::setName()
string nameOfBook;
cout << "Please enter the name of the book: ";
cin >> nameOfBook;
this->nameOfBook = nameOfBook;
string Book::getName()
return nameOfBook;
Library.h
#ifndef LIBRARY_H
#define LIBRARY_H
#include "Book.h"
#include <array>
class Library
private:
std::array <Book , 10> bookArray; // I have to use this
public:
void addBook();
void displayInfo();
;
#endif
Library.cpp
#include "Library.h"
#include "Book.h"
#include <iostream>
#include <string>
#include <array>
using namespace std;
void Library::addBook()
bookArray[0].setName();
void Library::displayInfo()
cout << "The book: " << bookArray[0].getName() << endl;
还有 main.cpp
#include <iostream>
#include "Book.h"
#include "Library.h"
#include <string>
#include <array>
using namespace std;
int main()
// The problem is solved
// Create the objects out of the loop
// Library obj1 <---- this solved it
while (true)
int number; // Ask user what to do
cout << "Press 1 to add a book\n"
<< "Press 2 to display info\n"
<< "Press 0 to quit\n";
cin >> number;
if (number == 1) // Add a book
Library obj1; // <------ THIS IS WRONG
obj1.addBook(); // Consider we named the book as 'Fly'
else if (number == 2)
Library obj1; // <------ THIS IS WRONG
obj1.displayInfo(); // ******* The output I'm expecting is The Book: Fly
// But instead, it only gives me The Book:
// I have 4 more strings like this in the main project and all of them have the same problem
else if (number == 0) // Everything else
break;
else
cout << "Wrong input\n";
continue;
编辑: 我用 VS Code 对此进行了编码,并在必要时用 MinGW (8.2.0) 对其进行了编译。
【问题讨论】:
【参考方案1】:您的代码中的一个问题是您有许多库类的实例,因此 addBook 登陆一个对象,而 displayInfo 登陆一个新对象(空的)
你必须:
int main()
Library obj1; // declare the lib in scope for all the cases
while (true)
int number; // Ask user what to do
cout << "Press 1 to add a book\n"
<< "Press 2 to display info\n"
<< "Press 0 to quit\n";
cin >> number;
if (number == 1) // Add a book
obj1.addBook(); // Consider we named the book as 'Fly'
else if (number == 2)
//Library obj1;
obj1.displayInfo(); // ******* The output I'm expecting is The Book: Fly
// But instead, it only gives me The Book:
// I have 4 more strings like this in the main project and all of them have the same problem
else if (number == 0) // Everything else
break;
else
cout << "Wrong input\n";
continue;
【讨论】:
【参考方案2】:你在循环的每次迭代中再次创建对象。因此覆盖已命名的旧对象。
【讨论】:
请在问题中添加解决问题的代码以上是关于对象数组打印空白字符串的主要内容,如果未能解决你的问题,请参考以下文章
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