#include <iostream>
#include <string>
#include <vector>
class Student {
public:
    std::string name;
    int age;
    Student(std::string n, int a) : name(n), age(a) {}
    // 拷貝構(gòu)造函數(shù)（用于演示傳值時(shí)的拷貝行為）
    Student(const Student& other) : name(other.name), age(other.age) {
        std::cout << "?? [拷貝構(gòu)造函數(shù)被調(diào)用]" << std::endl;
    }
};
// --- 1. 傳值 ---
// 這里的 s 是 originalStudent 的副本
void modifyByValue(Student s) {
    s.name = "Modified_Value";
    s.age = 99;
    std::cout << "函數(shù)內(nèi)(值): " << s.name << ", " << s.age << std::endl;
}
// --- 2. 傳引用 (非常用) ---
// 這里的 s 是 originalStudent 的別名
void modifyByReference(Student& s) {
    s.name = "Modified_Reference";
    s.age = 88;
    std::cout << "函數(shù)內(nèi)(引用): " << s.name << ", " << s.age << std::endl;
}
// --- 3. 常量引用 (最佳實(shí)踐) ---
// 既避免了拷貝，又防止了修改
void printStudent(const Student& s) {
    // s.name = "Error"; // 編譯錯(cuò)誤：不能修改 const 對象
    std::cout << "函數(shù)內(nèi)(只讀): " << s.name << ", " << s.age << std::endl;
}
int main() {
    Student originalStudent("Alice", 20);
    std::cout << "原始數(shù)據(jù): " << originalStudent.name << ", " << originalStudent.age << std::endl;
    std::cout << "--- 調(diào)用傳值函數(shù) ---" << std::endl;
    modifyByValue(originalStudent); 
    // originalStudent 未被修改，但觸發(fā)了拷貝構(gòu)造
    std::cout << "調(diào)用后: " << originalStudent.name << ", " << originalStudent.age << std::endl << std::endl;
    std::cout << "--- 調(diào)用傳引用函數(shù) ---" << std::endl;
    modifyByReference(originalStudent);
    // originalStudent 被修改了
    std::cout << "調(diào)用后: " << originalStudent.name << ", " << originalStudent.age << std::endl;
    return 0;
}

class Animal { public: virtual void speak() { cout << "..." << endl; } };
class Dog : public Animal { public: void speak() { cout << "Woof!" << endl; } };
void makeSound(Animal a) { a.speak(); } // 錯(cuò)誤：傳值會(huì)導(dǎo)致切片，Dog 變成 Animal
void makeSound(Animal& a) { a.speak(); } // 正確：傳引用保留多態(tài)性