2d pointer initializing in [closed] - c++

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I have this data member in my class:cell** rep. I want to set size of the 2d in constructor. I receive no error while compiling; but no result comes when i run it.
//main.cpp
#include <ctime>
#include <cstdlib>
#include "cell.h"
#include "world.h"
using namespace std;
int main(){
srand(time(0));
World Conway(6,6);
Conway.generateWorld();
int numAlive = 1;
do{
numAlive = Conway.print();
Conway.nextGeneration();
cout<<"\n\t\t\t*****************\n\n";
cin.get();
}while(numAlive);
cin.get();
return 0;
}
//cell.h
#ifndef CELL_H
#define CELL_H
class Cell {
private :
bool alive;
public :
Cell() ;
void setAlive(bool b);
bool isAlive();
};
#endif
//cell.cpp
#include "cell.h" // class's header file
Cell::Cell(){
alive = false;
}
void Cell::setAlive(bool b){
alive = b;
}
bool Cell::isAlive(){
return alive;
}
//world.h
#ifndef WORLD_H
#define WORLD_H
#include "Cell.h"
class World {
private :
bool ring;
int lines, columns ;
Cell** rep; //I could not write this with pointer
public :
World (int l, int c) ;
World (int l, int c, bool ring);
~World() ;
int getLines();
int getColumns();
void generateWorld();
int nbAliveNeighbor( int i, int j) ;
int nbAliveNeighborRing( int i, int j);
void nextGeneration();
int print(); //the output of this function help me to end main loop
} ;
#endif
//world.cpp
#include "world.h" // class's header file
#include <cstdlib>
#include <ctime>
#include <iostream>
using namespace std;
World::World (int l, int c) {
lines = l;
columns = c;
ring = false;
Cell **rep = 0;
// memory allocated for elements of rows.
rep = new Cell *[l];
// memory allocated for elements of each column.
for( int i = 0 ; i < l ; i++ ) {
rep[i] = new Cell[c];
}
}
World::World(int l,int c,bool r){
lines = l;
columns = c;
ring = r;
}
int World::getLines(){
return lines;
}
int World::getColumns(){
return columns;
}
int World::nbAliveNeighborRing( int i, int j){
int n = 0; //number of alives
for(int r = i-1; r < i+2; r++){
for(int c = j-1; c < j+2; c++){
//giving ring flexibility
if(c < 0)
c + columns;
if(c >= columns)
c - columns;
if(r < 0)
r + lines;
if(r >= lines)
r - lines;
if(c==j && r ==i)
continue; //ignoring the cell itself
if(rep[r][c].isAlive())
n++;
}
}
return n;
}
int World::nbAliveNeighbor( int i, int j) {
int n = 0; //number of alives
for(int r = i-1; r < i+2; r++){
for(int c = j-1; c < j+2; c++){
//ignoring if it's out of range
if(c < 0 || c >= columns)
continue;
if(r < 0 || r >= lines)
continue;
//ignoring the cell itself
if(c==j && r ==i)
continue;
if(rep[r][c].isAlive())
n++;
}
}
return n;
}
int random(int a,int b){
return a+rand()%(b-a+1); //including a & b
}
void World::generateWorld(){
int nAlive = (lines * columns)/ 4 + 1;
//why plus 1:
// because in random some are the same so we plus it with 1 so in the average
// the alive cells will be third of deads!
int randAry[nAlive];
for(int i=0, clm=0, row=0; i < nAlive; i++){
randAry[i] = random(0,lines*columns);
clm = 0;
row = 0;
while(randAry[i] >= lines){
row ++;
randAry[i] -= lines;
}
clm = randAry[i];
rep[row][clm].setAlive(true);
}
}
void World::nextGeneration(){
if(ring){
for(int i = 0; i < lines; i++){
for(int j = 0; j < columns; j++){
if(rep[i][j].isAlive()){
if(nbAliveNeighborRing(i,j) == 3 || nbAliveNeighborRing(i,j) == 2)
continue;
else
rep[i][j].setAlive(false);
}
else{
if(nbAliveNeighborRing(i,j) == 3)
rep[i][j].setAlive(true);
}
}
}
}
else{
for(int i = 0; i < lines; i++){
for(int j = 0; j < columns; j++){
if(rep[i][j].isAlive()){
if(nbAliveNeighbor(i,j) == 3 || nbAliveNeighbor(i,j) == 2){
continue;
}
else{
rep[i][j].setAlive(false);
}
}
else{
if(nbAliveNeighbor(i,j) == 3){
rep[i][j].setAlive(true);
}
}
}
}
}
}
int World::print(){
int n = 0;
for(int i = 0; i < lines; i++){
for(int j = 0; j < columns; j++){
if(rep[i][j].isAlive()){
cout<<" * ";
n++;
}
else
cout<<" - ";
}
cout<<endl;
}
return n;
}
World::~World(){
delete rep;
}

Answer 1

Your Cell** rep is never created. This should be done in the constructor. Now you're making int **rep = 0;, which doesn't seem to be used anywhere.
//int **rep = 0; //scratch this
rep = new Cell *[l];
// memory allocated for elements of each column.
for( int i = 0 ; i < l ; i++ ) {
rep[i] = new Cell[c];
}

Answer 2

Maybe that Cell.h is capitalized in include of world.h

Answer 3

In class World data member rep is defined as
class World {
private :
bool ring;
int lines, columns ;
Cell** rep; //I could not write this with pointer
...
However in the constructor you use a local variable rep that have type int ** and try to initialize that local variable that will be destroyed after exiting the constructor.
World::World (int l, int c) {
lines = l;
columns = c;
ring = false;
int **rep = 0;
// memory allocated for elements of rows.
rep = new int *[l];
// memory allocated for elements of each column.
for( int i = 0 ; i < l ; i++ ) {
rep[i] = new int[c];
}