箭头“->”从类调用函数时，分隔符崩溃 [英] the arrow '->' separator is crashing when calling function from class

问题描述

我正在为一个类工作，我正在使用类和类型类的指针来调用类中的某些函数，但是在代码块和Eclipse上崩溃了，我不知道$ b发生了什么$ b请注意，将x分配给y时会崩溃

I'm working on a project for class and I'm using classes and pointers of type class to call some functions in the class but it's crashing on Code Blocks and Eclipse and I don't know what is going on Note it crashes when assigning x with y

#include <iostream>

using namespace std;

class a{
private:
    int x;
public:
    void set_X(int y){
        x=y;
    }
};

int main()
{
    a *Ptr;
    Ptr->set_X(5);
}

推荐答案

a *Ptr;
Ptr->set_X(5);

您的 Ptr 没有指向任何东西。尝试在未初始化的指针上调用成员函数会导致未定义的行为。崩溃只是可能发生的或多或少的随机事件之一。

Your Ptr does not point to anything. Trying to invoke a member function on an uninitialised pointer results in undefined behaviour. Crashing is just one of the many more or less random things that can happen.

幸运的是，在您的示例中，无论如何您都不需要指针。您可以简单地写：

Luckily, in your example, you do not need a pointer anyway. You can simply write:

a my_a;
my_a.set_X(5);

指针通常指向动态分配的对象。如果这是您想要的，则必须使用 new 并相应地删除：

Pointers often point to dynamically allocated objects. If this is what you want, you must use new and delete accordingly:

a *Ptr = new a;
Ptr->set_X(5);
delete Ptr;

在现代C ++中， std :: unique_ptr 通常是一种更好的选择，因为您不必手动释放分配的内存，从而消除了许多潜在的编程错误：

In modern C++, std::unique_ptr is typically a superior alternative because you don't have to manually release the allocated memory, which removes a lot of potential programming errors:

auto Ptr = std::make_unique<a>();
Ptr->set_X(5);
// no delete necessary

这篇关于箭头“->”从类调用函数时，分隔符崩溃的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！