无法将值赋给类中的变量 [英] Can't assign a value to a variable inside a class

问题描述

#include <iostream>

using namespace std;

class Foo {

    int i;
    int * p = new int;
    *p = 5; // This doesn't worl
    // If I instead use  int * p = new int(5); it works.
};

为什么呢?我看到，这仅在类内部发生，如果我在主函数上编写了相同的代码，那么它应该可以工作.

Why that? I see that this only occurs inside a class, if I write the same code on the main function it should work.

推荐答案

此语法无效.您不能简单地在类定义中编写代码.相反，您可以编写一个函数，您的代码将在其中运行:

This syntax in invalid. You cannot simply write code inside a class definition. Instead, you can write a function and your code will work inside it:

class Foo {
public:
  void bar() {
    int * p = new int;
    *p = 5;
  }
};

int main(int argc, char ** argv) {
  Foo f;
  f.bar();
}

注意:您应该尽可能在单个语句中分配和初始化变量:

Note: You should prefer to allocate and initialize your variable in a single statement when possible:

int *p = new int(5);

代替:

int * p = new int;
*p = 5;

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