C++中调用复制(拷贝)函数的三种情况总结

int main(){
Point p1(1,2);
Point p2=p1;   //这两种都会调用复制构造函数
Point p3(p1);
return 0;
}

void fun(Point p){ //p 作为了形参
 
cout<<p.height<<endl;
 
}

void fun2(){
Point p1(1,3);
return p1;
}
 
//或者还有返回*this的形式
 
void fun3(){
Point p2(5,8);
x+=4;
y+=6;
return *this;
}

int main(){
MyString s1;
MyString s2("Hello");
MyString s3(s2);
 
s1.printString();
s2.printString();
s3.printString();
 
cout<<s1.getSize()<<" "<<s2.getSize()<<" "<<s3.getSize()<<endl;
 
MyString s4("HiChina"); 
 
s2.stringCopy(s4);
s2.printString();
 
s3.stringCat(s4);
s3.printString(); 
 
return 0;
}

//不包括主函数main部分
#include<bits/stdc++.h>
using namespace std;
class MyString{
 char *sptr;
 int size;
public:
 MyString(){
  size=0;
  sptr=new char[1];
  sptr[0]='\0';
  cout<<"Object Constructed. No Memory Allocated."<<endl;
 }
 MyString(char* s){//s是指针 
    size=strlen(s);
    sptr=new char[size+1];
    sptr[size]='\0';
    strcpy(sptr,s);
    cout<<"Object Constructed. "<<size+1<<" Bytes Allocated."<<endl;
 }
 MyString(const MyString&s){//此处s是对象 
  size=s.size;
  sptr=new char[size+1];
  strcpy(sptr,s.sptr);
  cout<<"Object Constructed. "<<size+1<<" Bytes Allocated."<<endl;
 }
 ~MyString(){
  if(sptr[0]=='\0'){cout<<"Object Destructed. No Memory Freed."<<endl;}
  else{
   cout<<"Object Destructed. "<<size+1<<" Bytes Freed."<<endl;
  }
  delete[]sptr;
 }
 void printString(){
  if(!size){cout<<"No Memory Allocated In This Object."<<endl;}
  else  cout<<sptr<<endl;
 }
 int getSize(){
     return size;
 }
void stringCopy(MyString&s){
  cout<<"String Copy, "<<s.size+1<<" Bytes Reallocated And "<<size+1<<" Bytes Freed."<<endl;
  size=s.size;
  sptr=new char[size+1];
  strcpy(sptr,s.sptr);
  sptr[s.size]='\0'; //没有return *this 
 }
 void stringCat(MyString&p){
  char *p1=new char [size+p.size+1];
  size=size+p.size;
  cout<<"String Connection, "<<size+1<<" Bytes Reallocated And "<<p.size-1<<" Bytes Freed."<<endl;
  strcpy(p1,sptr);//p1是换杯子 
  sptr=new char [size+p.size+1];//创建新的大空间 
  strcpy(sptr,p1);
  strcat(sptr,p.sptr);
  
 } 
};