c++详细讲解构造函数的拷贝流程

#include <iOStream>
#include <string>
using namespace std;
void func(string str){
    cout<<str<<endl;
}
int main(){
    string s1 = "Http:www.biancheng.net";
    string s2(s1);
    string s3 = s1;
    string s4 = s1 + " " + s2;
    func(s1);
    cout<<s1<<endl<<s2<<endl<<s3<<endl<<s4<<endl;
    return 0;
}

#include <iostream>
#include <string>
using namespace std;
class Student{
public:
    Student(string name = "", int age = 0, float score = 0.0f);  //普通构造函数
    Student(const Student &stu);  //拷贝构造函数（声明）
public:
    void display();
private:
    string m_name;
    int m_age;
    float m_score;
};
Student::Student(string name, int age, float score): m_name(name), m_age(age), m_score(score){ }
//拷贝构造函数（定义）
Student::Student(const Student &stu){
    this->m_name = stu.m_name;
    this->m_age = stu.m_age;
    this->m_score = stu.m_score;
    cout<<"Copy constructor was called."<<endl;
}
void Student::display(){
    cout<<m_name<<"的年龄是"<<m_age<<"，成绩是"<<m_score<<endl;
}
int main(){
   const Student stu1("小明", 16, 90.5);
    Student stu2 = stu1;  //调用拷贝构造函数
    Student stu3(stu1);  //调用拷贝构造函数
    stu1.display();
    stu2.display();
    stu3.display();
    return 0;
}

class Base{
public:
    Base(): m_a(0), m_b(0){ }
    Base(int a, int b): m_a(a), m_b(b){ }
private:
    int m_a;
    int m_b;
};
int main(){
    int a = 10;
    int b = a;  //拷贝
    Base obj1(10, 20);
    Base obj2 = obj1;  //拷贝
    return 0;
}

#include <iostream>
#include <cstdlib>
using namespace std;
//变长数组类
class Array{
public:
    Array(int len);
    Array(const Array &arr);  //拷贝构造函数
    ~Array();
public:
    int operator[](int i) const { return m_p[i]; }  //获取元素（读取）
    int &operator[](int i){ return m_p[i]; }  //获取元素（写入）
    int length() const { return m_len; }
private:
    int m_len;
    int *m_p;
};
Array::Array(int len): m_len(len){
    m_p = (int*)calloc( len, sizeof(int) );
}
Array::Array(const Array &arr){  //拷贝构造函数
    this->m_len = arr.m_len;
    this->m_p = (int*)calloc( this->m_len, sizeof(int) );
    memcpy( this->m_p, arr.m_p, m_len * sizeof(int) );
}
Array::~Array(){ free(m_p); }
//打印数组元素
void printArray(const Array &arr){
    int len = arr.length();
    for(int i=0; i<len; i++){
        if(i == len-1){
            cout<<arr[i]<<endl;
        }else{
            cout<<arr[i]<<", ";
        }
    }
}
int main(){
    Array arr1(10);
    for(int i=0; i<10; i++){
        arr1[i] = i;
    }
    Array arr2 = arr1;
    arr2[5] = 100;
    arr2[3] = 29;
    printArray(arr1);
    printArray(arr2);
    return 0;
}

#include <iostream>
#include <ctime>
#include <windows.h>  //在linux和Mac下要换成 unistd.h 头文件
using namespace std;
class Base{
public:
    Base(int a = 0, int b = 0);
    Base(const Base &obj);  //拷贝构造函数
public:
    int getCount() const { return m_count; }
    time_t getTime() const { return m_time; }
private:
    int m_a;
    int m_b;
    time_t m_time;  //对象创建时间
    static int m_count;  //创建过的对象的数目
};
int Base::m_count = 0;
Base::Base(int a, int b): m_a(a), m_b(b){
    m_count++;
    m_time = time((time_t*)NULL);
}
Base::Base(const Base &obj){  //拷贝构造函数
    this->m_a = obj.m_a;
    this->m_b = obj.m_b;
    this->m_count++;
    this->m_time = time((time_t*)NULL);
}
int main(){
    Base obj1(10, 20);
    cout<<"obj1: count = "<<obj1.getCount()<<", time = "<<obj1.getTime()<<endl;
    Sleep(3000);  //在Linux和Mac下要写作 sleep(3);
    Base obj2 = obj1;
    cout<<"obj2: count = "<<obj2.getCount()<<", time = "<<obj2.getTime()<<endl;
    return 0;
}