Question

我的问题是我的GetTitle（）函数没有返回值。

我的班级书的代码已经完成，我仍在完成项目的main（）代码并正在测试特定部分。我正在使用用户输入来测试我的函数，看看它们是否有效。

我正在测试的函数是SetTitle（）和GetTitle（）。我运行代码时没有收到任何错误，但我的GetTitle（）函数没有返回值。我已经谷歌搜索并查找其他类似的堆栈溢流问题，只是不明白为什么会发生这种情况。

我运行代码并输入字符串“Test”时的示例：

 Enter the book title:
 Test
    If this is after the book title the test worked

应该输出的是：

Enter the book title: 
Test
Test   If this is after the book title the test worked

我的代码

#include <iostream>
#include <string>
#include <cstdio>
using namespace std;

class Book {
public:
    void SetTitle(string title_input);
    string GetTitle();
    void SetAuthor(string& author_input);
    string GetAuthor();
    void SetCopyRightYear(int copyright_year_input);
    int GetCopyRightYear();
    void PrintBook();

private:
    string title;
    string author;
    int copyright_year;
};

 void Book::SetTitle(string title_input) {
      string title = title_input;
   }
     string Book::GetTitle() {
         return title;
     }
     void Book::SetAuthor(string& author_input) {
         string author = author_input;
     }
     string Book::GetAuthor() {
         return author;
     }
     void Book::SetCopyRightYear(int copyright_year_input) {
         int copyright_year = copyright_year_input;
     }
     int Book::GetCopyRightYear() {
         return copyright_year;
     }
     void Book::PrintBook() {
         cout << "Title of Book: " << GetTitle() << endl;
         cout << "Author of Book: " << GetAuthor() << endl;
         cout << "Copyright Year: " << GetCopyRightYear() << endl;
     }


int main ()
{
    string title_input = "";
    string author_input = "";
    int copyright_year_input = 0;


    Book book1;
    Book book2;
    Book book3;
    Book book4;

    cout << "Enter the book title: " << endl;
    cin >> title_input;
    book1.SetTitle(title_input);
    cout << book1.GetTitle() << "   If this is after the book title the test worked!" << endl;
}

Answer 1

因为您在setter中创建了一个局部变量并设置了它的值。它与您的对象无关

string title = title_input;

没有设置方法属性的值。将其更改为

title = title_input;

Answer 2

在函数setTitle中，您正在创建一个隐藏实际标题varibale的局部变量标题，因此不要在它之前使用string。这种方式改变了每个setter函数。

#include <iostream>
#include <string>
#include <cstdio>
using namespace std;

class Book {
public:
    void SetTitle(string title_input);
    string GetTitle();
    void SetAuthor(string& author_input);
    string GetAuthor();
    void SetCopyRightYear(int copyright_year_input);
    int GetCopyRightYear();
    void PrintBook();

private:
    string title;
    string author;
    int copyright_year;
};

void Book::SetTitle(string title_input) {
      title = title_input;
}
 string Book::GetTitle() {
     return title;
 }
 void Book::SetAuthor(string& author_input) {
      author = author_input;
 }
 string Book::GetAuthor() {
     return author;
 }
 void Book::SetCopyRightYear(int copyright_year_input) {
      copyright_year = copyright_year_input;
 }
 int Book::GetCopyRightYear() {
     return copyright_year;
 }
 void Book::PrintBook() {
     cout << "Title of Book: " << GetTitle() << endl;
     cout << "Author of Book: " << GetAuthor() << endl;
     cout << "Copyright Year: " << GetCopyRightYear() << endl;
 }


int main ()
{
    string title_input = "";
    string author_input = "";
    int copyright_year_input = 0;


    Book book1;
    Book book2;
    Book book3;
    Book book4;

    cout << "Enter the book title: " << endl;
    cin >> title_input;
    book1.SetTitle(title_input);

    cout << book1.GetTitle() << "   If this is after the book title the test worked!" << endl;
}

Answer 3

仔细查看您的SetTitle()功能。您声明一个本地字符串变量，其名称与您的成员字符串变量完全相同。调用函数时，只设置局部变量，而不是成员变量。

类成员函数get不会返回值

3 个答案: