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指针和引用

  1. 引用和指针都可以用来修改他们指向的对象内部状态
  2. 但是引用需要在声明的时候初始化，而且一旦指向某个对象，不会再改变；
  3. 对初始化的引用再次赋值，是对引用指向的对象进行赋值，引用本身始终指向最初的对象，它是那个对象的别名。
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#include <iostream>
void swapByPointer(int* a, int* b) {
    int temp = *a;
    *a = *b;
    *b = temp;
}
void swapByReference(int& a, int& b) {
    int temp = a;
    a = b;
    b = temp;
}
int main() {
    int x = 5;
    int y = 10;
    std::cout << "Before swapping: x = " << x << ", y = " << y << std::endl;
    // 使用指针交换变量的值
    swapByPointer(&x, &y);
    std::cout << "After swapping by pointer: x = " << x << ", y = " << y << std::endl;
    x = 5;
    y = 10;
    // 使用引用交换变量的值
    swapByReference(x, y);
    std::cout << "After swapping by reference: x = " << x << ", y = " << y << std::endl;
    return 0;
}

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#include <iostream>
using namespace std;
class Parent
{
public:
    virtual void v_test() { cout << "Parent::v_test" << endl; }
    int a = 0;
};
class Child : public Parent
{
public:
    void v_test() override { cout << "Child::v_test" << endl; }
};
int main()
{
    Parent parent;
    Child child;
    parent.a = 1;
    child.a = 2;
    Parent* p = &child;
    Parent& ref_parent = parent;
    cout << p->a << endl;
    cout << ref_parent.a << endl;
    // 对引用指向的对象进行赋值
    // 改变的是对象内部的值，a的值变了
    ref_parent = child;
    cout << ref_parent.a << endl;
    p->v_test();
    ref_parent.v_test();
    return 0;
}
输出 
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Child::v_test
Parent::v_test