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Posted by Adam on 10/10/06 11:59
Exactly what I needed, thank you!
petersprc@gmail.com wrote:
> Hi,
>
> In PHP4, objects were handled using copy-on-write semantics. In PHP5,
> this is no longer the case. In this code, you would probably want to
> make a copy of the cell objects using the clone operator, instead of
> referencing them. For instance:
>
> public function setInitialState() {
> // Clear the target array
> $this->initialState = array();
> // Iterate over the source objects
> foreach ($this->getCurrentState() as $cell) {
> // Use the clone operator to copy the object:
> $this->initialState[] = clone $cell;
> }
> }
>
> Some more info on cloning in PHP5:
>
> http://us2.php.net/manual/en/language.oop5.cloning.php
>
> The clone operator will by default create a shallow copy of an object.
> (You can change this behavior by implementing a __clone method in
> Cell.)
>
> FYI, here's an interesting look into PHP variable management:
>
>
> http://www.quepublishing.com/articles/article.asp?p=516587&seqNum=2&rl=1
>
> Adam wrote:
> > I am creating a program to create sudoku games. I have an object that
> > is 1 row of a sudoku game. I store the initial state of the row before
> > I start figuring out the values to place in each cell, in case the
> > program runs into a problem and has to revert the row back to its
> > original state.
> >
> > So first I store the initial State of the row, then I start to modify
> > the row. My problem is that once I start to change the original row,
> > it also changes the initial state that I saved. The only thing I can
> > think that is doing this is that instead of creating a copy of the
> > object's data in my initial state variable, it is just changing its
> > pointer to the original rows location.
> >
> > I wrote a smaller test case to show what I am talking about. At the
> > end of the program, each cell in the initial state should be full of
> > numbers 1 to 9. Instead, it is a copy of the current state of the row.
> >
> >
> > Hopefully someone can clue me in on what I am missing? You can see the
> > output of the program here
> > http://mustang.millersville.edu/~arisser/sudoku/test.php
> >
> > Thanks again for the help!!
> >
> > <?php
> > ###########################################################
> >
> > class Cell {
> > public $c = array(1,2,3,4,5,6,7,8,9);
> >
> > //_____________________________________________________
> >
> > public function getCandidates() {
> > return $this->c;
> > }
> >
> > //_____________________________________________________
> >
> > public function pickRandomCandidate() {
> > return $this->c[rand() % count($this->c)];
> > }
> >
> > //_____________________________________________________
> >
> > public function setCandidate($a) {
> > $this->c = array($a);
> > }
> >
> > //_____________________________________________________
> >
> > public function removeCandidateFromCell($v) {
> > $this->c = array_values(array_diff($this->c,array($v)));
> > }
> > }
> >
> > ###########################################################
> >
> > class Row {
> > public $cells = array();
> > public $initialState = array();
> >
> > //_____________________________________________________
> >
> > public function __construct() {
> > for ($i=0;$i<9;$i++)
> > $this->cells[$i] = new Cell();
> > }
> >
> > //_____________________________________________________
> >
> > public function getInitialState() {
> > return $this->initialState;
> > }
> >
> > public function getCurrentState() {
> > return $this->cells;
> > }
> >
> > //_____________________________________________________
> >
> > public function setInitialState() {
> > $this->initialState = $this->getCurrentState();
> > }
> >
> > //_____________________________________________________
> >
> > public function printRow() {
> > echo "<strong>Printing Row State</strong>";
> > echo "<table border=1 cellpadding=4>";
> > echo "<tr>";
> > foreach($this->cells as $cell) {
> > echo "<td align='center'>";
> > for($i=1; $i <= 9; $i++) {
> > echo (in_array($i, $cell->c)) ? $i : "<span style='color:
> > #ddd'>$i</span>";
> > echo $i==3 || $i==6 ? "<br />" : "";
> > }
> > echo "</td>";
> > }
> > echo "</tr>";
> >
> > echo"</table>";
> > }
> >
> > //_____________________________________________________
> >
> > public function printInitialState($rowNum = "") {
> > echo "<strong>Initial State of $rowNum</strong>";
> > echo "<table border=1 cellpadding=4>";
> > echo "<tr>";
> > foreach($this->initialState as $cell) {
> > echo "<td align='center'>";
> > for($i=1; $i <= 9; $i++) {
> > echo (in_array($i, $cell->c)) ? $i : "<span style='color:
> > #ddd'>$i</span>";
> > echo $i==3 || $i==6 ? "<br />" : "";
> > }
> > echo "</td>";
> > }
> > echo "</tr>";
> > echo"</table>";
> > }
> > //_____________________________________________________
> >
> > public function resetRow($rowNum = "") {
> > echo "resetting row $rowNum <br />";
> > $this->cells = $this->getInitialState();
> > #$this->cells = $this->initialState;
> > }
> >
> > //_____________________________________________________
> >
> > public function removeCandidateFromRow($v) {
> > foreach($this->cells as $c => $val) {
> > $val->removeCandidateFromCell($v);
> > }
> > }
> > }
> >
> > $myrow = new Row();
> >
> > $myrow->setInitialState();
> >
> > $candidate = $myrow->cells[0]->pickRandomCandidate();
> >
> > $myrow ->removeCandidateFromRow($candidate);
> > $myrow->cells[0]->setCandidate($candidate);
> >
> > $myrow->printRow();
> > $myrow->printInitialState();
> > ?>
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