My test program from learning "move constructor", "move assignment". For personal memo purpose.

#include <iostream>#include <string>/*When it comes to move assignment, we cannot just use std::swap(*this, rhs);It is because std::swap combines with three std::move commands: one is a moveconstructor, the other two are move assignments. So it will result in endlessrecursion from call move assignment within move assignment.*/using std::cin; using std::cout; using std::endl;class MetaData{public:    MetaData (int size, const std::string& name)        : _name( name )        , _size( size )    {    cout << "MetaData initialiser!" << endl;    }     // copy constructor    MetaData (const MetaData& other)        : _name( other._name )        , _size( other._size )    {    cout << "MetaData copy constructor!" << endl;    }     // move constructor    MetaData (MetaData&& other)        : _name( std::move(other._name) )        , _size( other._size )    {    cout << "MetaData move constructor!" << endl;    }MetaData &operator= (MetaData &other){if(this != &other){_name = other._name;_size = other._size;}cout << "MetaData copy assignment!" << endl;return *this;}  MetaData &operator= (MetaData &&other){if(this != &other){_name = other._name;_size = other._size;other._name = "";other._size = 0;}cout << "MetaData move assignment!" << endl;return *this;}     std::string getName () const { return _name; }    int getSize () const { return _size; }private:    std::string _name;    int _size;};class ArrayWrapper{public:    // default constructor produces a moderately sized array    ArrayWrapper ()        : _p_vals( new int[ 64 ] )        , _metadata( 64, "ArrayWrapper" )    {}     ArrayWrapper (int n)        : _p_vals( new int[ n ] )        , _metadata( n, "ArrayWrapper" )    {}     // move constructor    ArrayWrapper (ArrayWrapper&& other)        : _p_vals( other._p_vals  )        , _metadata( std::move(other._metadata) )    {        cout << "ArrayWrapper move constructor!" << endl;other._p_vals = NULL;    }     // copy constructor    ArrayWrapper (const ArrayWrapper& other)        : _p_vals( new int[ other._metadata.getSize() ] )        , _metadata( other._metadata )    {        for ( int i = 0; i < _metadata.getSize(); ++i )        {            _p_vals[ i ] = other._p_vals[ i ];        }    }    ~ArrayWrapper ()    {        delete [] _p_vals;    }private:    int *_p_vals;    MetaData _metadata;};class Integer{public:Integer(int n, std::string s):elem(n),str(s){cout << "Integer initialiser!" << endl;}Integer(const Integer &val):elem(val.elem){str = "COPY";cout << "Integer copy constructor!" << endl;}Integer(Integer &&val):elem(val.elem){str = "MOVE";cout << "Integer move constructor!" << endl;}Integer &operator=(const Integer &val){cout << "****** Integer copy assignment begins! ******" << endl;// if(this != &val)// {// elem = val.elem;// str = val.str;// cout << "Integer copy assignment!" << endl;// }Integer copy = val;std::swap(*this, copy);cout << "********* Integer copy assignment ends *******" << endl;return *this;}Integer &operator=(Integer &&val){cout << "******* Integer move assignment begins! *******" << endl;std::swap(elem, val.elem);std::swap(str, val.str);cout << "******* Integer move assignment ends! *******" << endl;return *this;}std::string getVal(){return str;}private:int elem;std::string str;};Integer ret(){Integer tmp(100, "tmp");return tmp;}int main(){// ArrayWrapper aw1;// ArrayWrapper aw3(aw1);Integer i1(99,"i1");Integer i2(100,"i2");// cout << i2.getVal() << endl;i2 = {1, "haha"};cout << endl;i2= i1;cout << i2.getVal() << endl;return 0;}