c++ 传递对象的私有(private)变量

Question

#include <stdio.h>

class HelloClass
{
    float t;
public:
    HelloClass(float x) : t(x) {};
    float Add(HelloClass a);
};

float HelloClass::Add(HelloClass b)
{
    return t + b.t; // How is b.t accessible here?
}

int main()
{
    HelloClass a(2), b(3);
    printf("hello %f\n", a.Add(b));
    return 0;
}

你好，上面的代码编译成功了。但我无法理解 b.t可以访问吗？有人可以对此有所了解吗？

Answer 1

这是预期的行为， private members可以被成员函数访问，即使它们来自其他实例。
(强调我的)

A private member of a class is only accessible to the members andfriends of that class, regardless of whether the members are on thesame or different instances:

class S {
  private:
    int n; // S::n is private
  public:
    S() : n(10) {}                    // this->n is accessible in S::S
    S(const S& other) : n(other.n) {} // other.n is accessible in S::S
};