如何释放动态struct数组的内存 [英] How to free memory of dynamic struct array

问题描述

作为从未处理释放内存等等的人，我得到了创建一个动态数组的结构和创建函数来添加或删除数组元素的任务。当删除我必须释放不再需要的内存。

As someone who never dealt with freeing memory and so on, I got the task to create a dynamic array of struct and create functions to add or delete array elements. When deleting I have to free the memory which is no longer necessary.

当删除3的数组的第二个元素时，我将第三个元素移动到第二位置，然后删除最后一个。当删除最后一个，我总是得到一个错误...有没有人可以找到一个解决方案给我？

when deleting the 2nd element of an array of the size of 3, I move the 3rd element to the 2nd position and then delete the last one. When deleting the last one, I always get an error... Is there anyone who can find an solution for me?

struct myFriend {
    myFriend() {
        number=0;
        hobbys = new char*[10];
    }
    int number;
    char* name;
    char** hobbys;
};
int main() {
    myFriend* friendList = new myFriend[10];

    myFriend* tempFriend = new myFriend;
    tempFriend->number=1;
    tempFriend->name = "ABC";

    myFriend* tempFriend2 = new myFriend;
    tempFriend2->number=2;
    tempFriend->name = "XYZ";

    myFriend* tempFriend3 = new myFriend;
    tempFriend3->number=3;
    tempFriend3->name = "123";

    friendList[0] = *tempFriend;
    friendList[1] = *tempFriend2;
    friendList[2] = *tempFriend3;

    friendList[1] = friendList[2]; //move 3rd element on 2nd position
    delete &(friendList[2]); //and delete 3rd element to free memory
}

推荐答案

我注意到两件事。 （1）你显然应该创建函数来添加或删除元素，但你还没有这样做，你只创建了一个函数。 （2）你正在通过使用一个也需要管理内存的结构，使你的工作比它需要的更加困难。我建议你使用一个更简单的结构。

Two things I noticed. (1) You are apparently supposed to "create functions to add or delete elements" but you haven't done that, you have only created one function. (2) You are making your work harder than it needs to be by using a struct that also needs to manage memory. I suggest you use a simpler struct.

你的任务实际上是一个简单的'vector'类，所以我建议你这样做。从一个空的结构开始。如果老师要求您使用 myFriend 结构作为书面语句，您可以在之后在之后添加它。我会假设你不允许做一个类，因为大多数教练犯了错误，直到最后。

Your assignment is, in effect, to make a simple 'vector' class, so I suggest that you do that. Start with a struct that is empty. If the teacher requires you to use the myFriend struct as written, you can add that in after you finish making your vector like functions. I'm going to assume that you aren't allowed to make a class yet because most instructors make the mistake of leaving that until last.

struct MyStruct {
    int value; // start with just one value here. Dealing with pointers is more advanced.
};

MyStruct* array;
int size;
int capacity;

void addMyStruct(MyStruct& value); // adds a MyStruct object to the end.
void removeMyStructAtPosition(int position); // removes the MyStruct object that is at 'position'

// I leave the functions for you to implement, it's your homework after all, but I give some clues below.

void addMyStruct(MyStruct& value) {
    // First check that there is enough capacity in your array to hold the new value. 
    // If not, then make a bigger array, and copy all the contents of the old array to the new one.
    // (The first time through, you will also have to create the array.)
    // Next assign the new value to array[size]; and increment size
}

void removeMyStructAtPosition(int position) {
    // If the position is at end (size - 1,) then simply decrement size.
    // Otherwise you have to push all the structs one to the left (array[i] = array[i + 1])
    // from position to the end of the array.
}

int main() {
    // test your new class here.
    // don't forget to delete or delete [] any memory that you newed.
}

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