Question

我在更改字符串数组的值时遇到问题。代码的要点是检查它的故事编号，然后更改字符串数组的值，然后通过forloop将它打印在choices函数中。

void CheckDecisions(std::string choices[], int num_choices, int story_number)
{
    //choices = new std::string[];
    const int num = 4;
    num_choices = num;

    if (story_number == 0)
    {
        std::string start_choices[num] = { "", "Home", "The Store", "Your friend Taylor's place" };
        choices = start_choices;
    }

    if (story_number == 1)
    {
        //std::string_choices[num_choices] = { "", "Hummana", "Hummana", "Yes!" };
    }
}

它不会更改字符串的值并仍然返回空。什么是正确的语法？

以下是整个代码：

#include <iostream>
#include <string>
#include <vector>


void CheckStoryArk(int choice, std::string story, int story_number)
{
    if (story_number == 0)
    {

        if (story == "Home")
        {
            printf("story is Home\n");
        }

        if (story == "The Store")
        {
            printf("Story is Store\n");
        }

        if (story == "Your friend Taylor's place")
        {
            printf("Story is Taylor\n");
        }
    }



    if (story_number == 1)
    {
        if (story == "whatever")
        {
            printf("something");
        }
    }



    if (story_number == 2)
    {
        printf("story number is 3\n");
    }

    if (story_number == 3)
    {
        printf("story number is the end\n");
    }
}



void CheckDecisions(std::string choices[], int num_choices, int story_number)
{
    //choices = new std::string[];
    const int num = 4;
    num_choices = num;

    if (story_number == 0)
    {
        std::string start_choices[num] = { "", "Home", "The Store", "Your friend Taylor's place" };
        choices = start_choices;
    }

    if (story_number == 1)
    {
        //std::string_choices[num_choices] = { "", "Hummana", "Hummana", "Yes!"      };
    }
}




//Prints out choices
void Choices(int num_choices, std::string choices[], int choice, std::string story, int story_number)
{
    CheckDecisions(choices, num_choices, story_number);

    for (int i = 1; i < num_choices; i++)
    {
        //printf("%d %s\n", i, choices[i]);
        std::cout << i << " " << choices[i] << "\n";
    }

    std::cin >> choice;
    if(choice >= num_choices)
    {
        printf("That's not a valid answer, dickbag!\n");
        std::cin >> choice;
    }

    story = choices[choice];

    CheckStoryArk(choice, story, story_number);
}


void Story(int story_number, const int num_choices, std::string choices[], int choice)
{
    printf("You're driving down the streets of Los Angeles, where are you going?\n");

    for (int i = 0; i < story_number; i++)
    {
        Choices(num_choices, choices, choice, choices[choice], i);      
    }
}

void main()
{
    const int num_choices = 4;
    int story_number = 4;
    int choice = 0;
    std::string choices[num_choices] = {};

    Story(story_number, num_choices, choices, choice);
}

Answer 1

这不是你的语法问题，而是你正在调用未定义的行为。

std::string start_choices[num] = { "", "Home", "The Store", "Your friend Taylor's place" };
choices = start_choices;

当您的函数存在时，start_choices数组将被销毁，因此将其分配给choices并尝试使用该函数访问它是未定义的。

而是将数据复制到choices数组中：

std::copy (std::begin(start_choices), std::end(start_choices), choices);

或者只是使用std::vector并完全避免头痛。

如何更改函数中的字符串数组

1 个答案: