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Why doesn't JS provide a simple way to perform a deep copy on objects?

By : patty
Date : September 15 2020, 10:00 AM
fixed the issue. Will look into that further
a) In a language where all variables are anyway treated as objects, why does the = operator distinguish [...] ?
code :

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Why doesn't the .NET framework provide a method to deep copy objects?

By : Gökhan Kurt
Date : March 29 2020, 07:55 AM
Hope that helps The problem is substantially harder than you seem to realize, at least in the general case.
For starters, a copy isn't just deep or shallow, it's a spectrum.

How to deep-copy closure objects (private objects) while Deep Copying

By : Tamara
Date : March 29 2020, 07:55 AM
Hope this helps It's not a good solution as all functions accessing your "private" cells variable have to declared as this.someFunction instead of Board.prototype so each Board instance will have their own funcions instead of sharing them.
Here is some sample code that would break prototype (c instanceof b is not true) but since you can't use prototype because you need to access closure variables in your functions that would not matter.
code :
function Test(privates) { 
    var msg = [];
    this.Message = function(newMsg) {
        if (newMsg) {
        } else {
            return msg;
      var orgMsg=msg
      var ret = function(){
      return deepCopy(this,new ret());
// this does not set prototype correctly
function deepCopy(from,to) {
    if(from == null || typeof(from) != 'object') {
        return from;
    for(var key in from) {
      // this.Message has closure ref to msg
      // you can't copy it because we've set a new
      // closure ref
      if(typeof from[key]!=="function"){
        to[key] = deepCopy(from[key]);
    return to;  

var b = new Test();
b.Message("Before cloning");
console.log("b message before cloning:",b.Message());
var c = b.clone();
console.log("c message after cloning:",c.Message());
b.Message("From BB after Clone");
console.log("c message after pushing new item in b:",c.Message());
c.Message("From CC after Clone");
console.log("b message after pushing new item in c:",b.Message());
console.log("c message after pushing new item in b:",c.Message());
 //here the msg variable doesn't exist

Does Job(Configuration conf) perform shallow copy or deep copy?

By : Naveen Sagar
Date : March 29 2020, 07:55 AM
wish helps you Here is the link to the current Job.java source. A quick glance shows that constructor calls super(conf, null);, so we need to grab the super class (JobContext) for a peek. The relevant line in that constructor is here:
code :
this.conf = new org.apache.hadoop.mapred.JobConf(conf);

Provide simplest example where deep copy is needed in ruby

By : Simon C
Date : March 29 2020, 07:55 AM
it should still fix some issue The example you have shown does not describe the difference between a deep and a shallow copy. Instead, consider this example:
code :
class Klass
  attr_accessor :name

anna = Klass.new
anna.name = 'Anna'

anna_lisa = anna.dup
anna_lisa.name << ' Lisa'
# => "Anna Lisa"

# => "Anna Lisa"
anna_lena = Marshal.load( Marshal.dump(anna))

How do you perform a deep copy on an object? How do you make a copy constructor?

By : user3505793
Date : March 29 2020, 07:55 AM
it should still fix some issue You should implement copy constructors and copy assignment operators and take care when using new. You need one delete for each new - unless you surrender the pointer returned by new to a smart pointer. In C++03 you have std::auto_ptr that can be used to manage the memory resources for you.
Here's an example with comments inline:
code :
#include <iostream>
#include <memory>    // std::auto_ptr
#include <algorithm> // std::swap (<algorithm> in c++03, <utility> in >= c++11) 

class Piece {
    // A virtual destructor to support deleting via base class pointer:
    virtual ~Piece() {}

    // You can't make constructors virtual, so add a clone()
    // function for copy constuction through a base class pointer
    virtual std::auto_ptr<Piece> clone() const = 0;

    // renamed get() into symbol()
    virtual char symbol() const = 0;

class One : public Piece {
    // Use the implicit copy constructor for One and return a (smart) pointer
    // to the base class.
    std::auto_ptr<Piece> clone() const {
        return std::auto_ptr<Piece>(new One(*this));
    char symbol() const { return '1'; }

class Two : public Piece {
    std::auto_ptr<Piece> clone() const {
        return std::auto_ptr<Piece>(new Two(*this));
    char symbol() const { return '2'; }

class Tile {
    std::auto_ptr<Piece> occ;  // this now handles delete for you

    Tile() : occ(NULL) {}      // default constructor
    Tile(Piece* p) : occ(p) {} // put pointer in auto_ptr

    // copy constructor, use the clone() function and conversion
    // to bool operator below. If "o" doesn't have a Piece, initialize occ
    // with an default constructed, empty, auto_ptr<Piece>.
    Tile(const Tile& o) : occ(o ? o.occ->clone() : std::auto_ptr<Piece>()) {}
    //                        ^
    //                        |
    //                        +--- conversion to bool in use

    // copy assignment operator
    Tile& operator=(const Tile& o) {
        Tile tmp(o);   // use the copy constructor above
        occ = tmp.occ; // steal pointer from tmp
        return *this;

    // converting assignment operator
    Tile& operator=(Piece* p) {
        // delete the old pointer and replace it with p:
        return *this;

    // Conversion to bool operator using std::auto_ptr's built in get()
    // to tell us if we have a Piece or not.
    operator bool() const { return occ.get() != NULL; }

    // Add a symbol() function to hide the logic to determine if this Tile
    // has a Piece or not.
    char symbol() const {
        // Check if there is a Piece in this Tile using the conversion
        // to bool operator here too:
            return occ->symbol();
            return '-'; // no Piece here

// add support to stream a Tile to an ostream
std::ostream& operator<<(std::ostream& os, const Tile& t) {
    return os << t.symbol();

class Board {
    Tile tiles[2][2];

    Board() {
        // using the added operator() further down
        (*this)(0,0) = new One;
        (*this)(0,1) = new Two;
        (*this)(1,1) = new One;

    // Note that cols and rows in arrays are usually seen as reversed.
    // tiles[2][2]               usually means:
    // tiles[<rows>=2][<cols>=2]

    // getTile() replacements - the interface here is still (col, row)
    // but it accesses the tiles[][] using the common form (row, col)
    Tile& operator()(int c, int r) { return tiles[r][c]; }
    Tile const& operator()(int c, int r) const { return tiles[r][c]; }

    // moving by swapping tiles
    void move(int c1, int r1, int c2, int r2) {
        // using operator() and the standard function std::swap
        std::swap((*this)(c1, r1), (*this)(c2, r2));

// Add a stream operator to not have to call print() explicitly when streaming
std::ostream& operator<<(std::ostream& os, const Board& b) {
    for(int r = 0; r < 2; r++) {
        for(int c = 0; c < 2; c++) {
            // Use "Board::operator() const" and stream support for returned
            // Tile.
            os << b(c, r);
        os << '\n';
    os << '\n';
    return os;

int main() {
    // no need to "new" anything:

    Board oldBoard;
    Board newBoard(oldBoard); // use copy constructor

    // use streaming operators
    std::cout << "Old board: \n" << oldBoard;
    std::cout << "New board: \n" << newBoard;

    // using the getTile() replacement, Board::operator():
    std::cout << "New board @ tile 1,0: " << newBoard(1, 0) << " before move\n";

    newBoard.move(0, 0, 1, 0);
    std::cout << "New board @ tile 1,0: " << newBoard(1, 0) << " after move\n\n";

    std::cout << "New board after move:\n" << newBoard;

    newBoard = oldBoard; // copy assignment operator
    std::cout << "New board after reinit:\n" << newBoard;
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