指向动态内存中结构中的变量时出现问题

Problem pointing to a variable in a structure in dynamic memory

本文关键字：问题 变量 结构 动态 内存      更新时间：2023-10-16

我似乎无法将值输入到我已经声明的结构中。我不确定这是语法错误还是逻辑错误。

我已经尝试更改语法，但总是以相同的错误告终。

struct Book{
string title;
Book* next;
};
Book bookName;
Book author;

Book* add_node(Book* in_root){
cout <<"Enter Book name n";
cin >> bookName.title;
cout << "Enter author name n";
cin >> author;
author = new Book();
Book -> Book.next = author;
}

在代码的这一部分中遇到错误：

cout << "Enter author name n";
cin >> author;
author = new Book();
Book -> Book.next = author;

首先，代码中有几个逻辑错误。

  • 绝对没有必要有两本书命名为bookName和author，除非我误解了它们的目的。
  • Book ->和Book.next是无效逻辑，因为您告诉它对数据类型进行操作Book，而不是类型Book的对象。

您可能想要的代码应如下所示：

#include <iostream>
#include <string>
using namespace std;
struct Book{
string title;
string author_name; // You potentially wanted this?
Book* next;
};
// This function assumes that `current_node->next` is `nullptr`
// The reasons for this is that making it handle such cases might be too difficult for you yet.
Book* add_node(Book* current_book){
if(current_book == nullptr){
cout << "Cannot link a new book to an non-existant book!n";
return nullptr;
}
Book* new_book = new Book();
cout <<"Enter the book namen";
cin >> new_book->title;
cout << "Enter the author namen";
cin >> new_book->author_name;
new_book->next = nullptr;
current_book->next = new_book;
return new_book;
}
int main(){
Book* book = new Book();
book->next = nullptr;
cout <<"Enter the name of the first bookn";
cin >> book->title;
cout << "Enter the name of the first book's authorn";
cin >> book->author_name;
add_node(add_node(book));
return 0;
}

我没有让函数在current_book->next != nullptr时处理情况的原因是因为它需要使用指向指针的指针。 如果你对它感兴趣，这里是：

Book* add_node_v2(Book* current_book){
if(current_book == nullptr){
cout << "Cannot link a new book to an non-existant book!n";
return nullptr;
}
Book* new_book = new Book();
cout <<"Enter the book namen";
cin >> new_book->title;
cout << "Enter the author namen";
cin >> new_book->author_name;
new_book->next = nullptr;
// Move to the last book in the chain
Book** ptr_to_next = &current_book->next;
while(*ptr_to_next != nullptr){
ptr_to_next = &(*ptr_to_next)->next; 
}
*ptr_to_next = new_book;
return new_book;
}

请记住，您最终将不得不delete链中的所有书籍。

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