Thread: Dynamic memory. Output problems.

Hello there. I'm working with dynamic memory right now and I wrote a code. I got a problem with my output and dont know how to fix it. I've 3 files w3.cpp weather.h weather.cpp. I assume that the problem is in the w3.cpp file. Could you help me to fix it? The problem : every time I run my code. The second/3rd/4th etc date is missing. The compiler doesnt let me to input something.

Code:

//My input/output

Weather Data
=====================
Days of Weather: 3
Enter date:
May 10
Enter high:
15
Enter low :
10
Enter date: // THIS IS MY PROBLEM
Enter high:
19
Enter low :
15
Enter date:
Enter high:
20
Enter low :
19


Weather report:
==================
May 10 15  10  


 19  15  


 20  19

Code:

//w3.cpp

//w3.cpp
//Last changes : 30/5/2015
#include <iostream>
#include <string.h>
#include "weather.h"
using namespace std;


int main(){
    
    int n;
    Weather* weather = NULL ;
    
    cout << "Weather Data\n";
    cout << "=====================" << endl;
    cout << "Days of Weather: ";
    cin >> n;
    cin.ignore();
    // allocate dynamic memory here
    
    weather = new (nothrow) Weather[n];
    
    
    
    for(int i = 0; i < n; i++){
        char date_description[31];
        double high=0.0, low=0.0;
  
        cout << "Enter date:\n";
        
        cin.getline(date_description,31);
        //cin >> date_description;
        cout << "Enter high:\n";
        cin >> high;
        cout <<"Enter low :\n";
        cin >> low;
        
        weather[i].set(date_description,high,low);
        strcpy( date_description, "" );
    }
    cout << endl;
    cout << "Weather report:\n";
    cout << "==================" << endl;
    
    for(int i = 0; i < n; i++){
        weather[i].display();
        cout << endl;
    }
    
    
    delete[] weather;
    weather = NULL;


    return 0;
    
}
// cout<<left<< setfill(" ")<<variables;

Code:

//weather.h
//Last changes: 30/05/2015
class Weather{
    char _weather_array[31]; 
    double _high;
    double _low;
public:
    void set(char (&date_description)[31],double &high,double &low);
    void display() const;
};

Code:

//weather.cpp
//Last changes : 30/05/2015
#include <iostream>
#include <string.h>
#include "weather.h"


using namespace std;


void Weather::set(char (&date_description)[31],double &high,double &low){
    strcpy (_weather_array,date_description);
    /*for (int i = 0; i<31;i++){
    _weather_array[i] = date_description[i];
    }*/
    _high = high;
    _low = low;
}


void Weather::display() const{
    cout << _weather_array<<" "<< _high<<"  "<<_low<<"  "<< endl;
}

By the way, I noticed:

Code:

weather = new (nothrow) Weather[n];

I suggest that you do not use nothrow new. Rather, either catch std::bad_alloc or allow it to propagate. If you do want to use nothrow new, then you should check that weather is not a null pointer before proceeding to dereference it.

Actually, it would be better if you just used a std::vector<Weather>. For practice with dynamic memory allocation without using standard containers, write a WeatherContainer class (or something like that) that does the RAII.

Also, instead of an array of 31 char to stor a null terminated string, have you considered std::string?

Note that your headers should have inclusion guards.