why doesn't work

hi
i try to make a dynamic array inside a loop but i have a problem
i want restore each time in the loop a name and print it out the delete the array the the loop go on the add other name the print it then delete it .....
but it didn't work with me , any idea?
here is my code:

i try to creat dynamic name inside a loop but/....!

Code:

i try to creat dynamic name inside a loop but/....!

int main()
{
char *names = NULL;
for (int i=0; i<3; i++)
{
if(names)
{
cout<<"yes"<<endl;
delete[]names;
names=NULL;
}
cout << "1- Enter the name : ";
names=new char [size];
cin.get (names , size);
char k;
do
{
cin.get(k);
}while(k!='\n');
cout<<names;
}
return 0;
}

So what compiler errors (if any) do you get? Or what's the problem if it compiles fine?

I don't see any problems besides 'size' being undeclared.

maro, do you have to use char* to store the name? If not, it would be a lot easier to use std::string instead.
Also, if you have to use an array, there is no need to delete the array, just overwrite what's in it each time. Or if you really want to delete it, do it at the bottom of the loop. I think the code doesn't compile though because youre using cin in a wrong way.
Here is what i would do:

Code:

#include <iostream>
#include <string>

int main(int argc, char *argv[]) {
  using namespace std;

  std::string names = "";
   for (int i=0; i<3; i++)
  {
    cout << "1- Enter the name : ";
    cin>>names;
    cout<<names<<"\n";
  }

  return 0;
}

Oh yes, and the size is undeclared

first i would like to thank you for answring my Q

My code is a part of a class Car

in the main i need to creat an array with objects ..
3 objects need to be created
so 3 different names for 3 cars

and about using std :: string , i can't use it coz still i didn't see it at the school

,, the error is the the first time the loop executing it asks the name so no problem then i delete the name Dynamic array to creat a new one with a new name
then the loop will excuting the second time but i can't add the second name ..... any idea

sorry for my bad english

It seems to work fine for me (with the definition of 'size'). You might be trying to enter a string that is too long, however. Try changing input code so that it checks for invalid input:

Code:

//change this
/*
cin.get (names , size);
char k;
do
{
cin.get(k);
}while(k!='\n');
*/
//to this
if (!cin.getline (names , size))//use getline so it removes the '\n'
{                                           //(getline returns the stream state)
  cout<<"Invalid input";
  cin.clear();
  cin.ignore(numeric_limits<int>::max(),'\n');
}

Also, make sure 'size' is a large enough value to hold a name.

Actually, re-reading your post, it sounds like you might want to store three names at once, in which case you would need an array of char* and you wouldn't want to delete after each loop...

Edit: You will also need to #include <limits> to use the numeric_limits class

hi JaWiB
thank you very much for your help but:
i just start with c++ and all what you said is very Difficult for me ..
and the size in my header file is 100
look let me do it more easly :


if i ask you to creat a pointer that point to Dynamic array.
now creat for loop that will execute 3 times.
***************************************
the first time you will creat the dynamic array and the pointer will point to it.
then the user will add a name inside this array.
then clean the buffer
then print out this name.
then delete this dynamic array and let the pointer point to NULL
**************************************
the for loop will execute the second time
will creat the new dynamic array and the pointer will point to it.
and ........etc
***********************************
is it possible to creat this?
coz as i told you im just a beginner .
thanks

What you posted works fine for me. Maybe post your whole source file. Like I said, from what I see, it should work...

ok here is my code

1st Header file :

Code:

#ifndef __dclass_h
#define __dclass_h

const int size =50;
void  clearBuf();
void menu();

class Car
{
	private:
		int   _nr_parts;
		int    _hp;
		float *_parts;
		char  *_brandname;
		

	public:
		 Car  (void);
		 Car  (int hp, float *parts, int nr_parts, const char *name);
		~Car  (void);

		void  set_hp (int hp);
		int   get_hp (void)const;

		void  set_brandname (const char *name);
		char  get_brandname ()const;

		void  set_Car (int hp,float *parts,int nr_parts, const char *brandname);

		void  print_car (void)const;

		void  add_part (int part_nr);
		void  remove_part (int part_nr);

		void  add_parts    (float *part_nrs, int nr_parts);
		void  remove_parts (float *part_nrs, int nr_parts);

};

#endif

2nd CPP file:

Code:

#include "D_class.h"
#include <iostream>
#include <cstring>

using namespace std;

void  clearBuf()  // this function to clear the buffer
{
	char k;
	do
	{
		cin.get(k);
	}while(k!='\n');
}

Car::Car  () //defualt constructor
{
	 _nr_parts  = 0;
	 _hp        = 0;
	 _parts     = NULL;
	 _brandname = NULL;
	
}

Car::Car  (int hp, float *parts, int nr_parts, const char *name) 
{
	_hp         = 0;
	_parts     = NULL;
	_brandname = NULL;
	_nr_parts  = 0;
	set_Car(hp,	parts, nr_parts, name);
	
}

Car::~Car  (void) //destructor
{
		cout<<"Destructor****"<<endl;
		if(_parts)
		{
			delete[]_parts;
			_parts=NULL;
			cout << "Dynamic parts deleted.."<<endl;
		}
		
		if(_brandname)
		{
			delete[]_brandname;
			_brandname=NULL;
			cout << "Dynamic name deleted.."<<endl;	
		}
		else
		{
			cout<<"something wrong"<<endl;
		}
	
}

//Set functions

void Car::set_hp (int hp)
{
	_hp = hp;
}

void Car::set_brandname (const char *name)
{
	int length = strlen(name)+1; 
	_brandname = new char [length];
	strcpy(_brandname,name);
}

void Car::add_part (int part_nr)
{
	_nr_parts = _nr_parts + part_nr;
}

void Car::remove_part (int part_nr)
{
	if(_nr_parts>part_nr)
	{
		_nr_parts = _nr_parts - part_nr;
	}
	else
	{
		cout<< "you will remove all parts"<<endl;
		_nr_parts=0;
	}
		
}


void Car::add_parts    (float *part_nrs, int nr_parts)
{
	if (part_nrs)
	{
			cout << "What is the cost of the new parts ? "<<endl;
					for(int m=0;m<nr_parts ; m++) // add values into the array
					{
						cout << "Part nr ("<<m+1<<") costs : ";
						cin  >> *(part_nrs+m);
					}	
		//Step 1 call add part function to set the length of the all array
		add_part (nr_parts);

		//Step 2 creat temp array to store the 2 arrays
		float *temp = new float [_nr_parts];
		if (temp)
		{
			if (_parts)
			{
					cout<<"\nThis nooooooooooooooooooooo work";
					for (int k=0; k< (_nr_parts); k++)
				{
					*(temp + k) = *(_parts + k);
				}

				for (int j = (_nr_parts - nr_parts) ; j<(_nr_parts) ; j++)
				{
					*(temp + j) = *(part_nrs+j);
				}
			}
		
			else if (_parts == NULL)
			{
					cout<<"\ntest that _part point to NULL"<<endl;
				for (int m=0; m< _nr_parts; m++)
				{
					*(temp + m) = *(part_nrs+m);
				}
			}
			delete []_parts;
			_parts=temp;
		}
		else
			cout<<"no temp created"<<endl;
	}
	else 
		cout<<"no Dynamic array created... "<<endl;
	
}


void Car::remove_parts (float *part_nrs, int nr_parts)
{
	cout<<"Remove Function"<<endl;
	if (part_nrs)
	{
			cout<<"\ntest if i pass D array"<<endl;
		// the following part is to store what will be removed
		if (_nr_parts>0)
		{
				for (int k=(_nr_parts-nr_parts-1); k<nr_parts; k++)
				{
						*(part_nrs+k)=*(_parts+k);
						cout<<"Part nr("<<k+1<<") with price of <"<<*(part_nrs+k)<<">will be remove"<<endl;
				}
				
		}
		else
		{
			cout<<"there is no items to be remove.....!!!!!"<<endl;
			delete[]_parts;
		}

		// now start remove the parts
		remove_part (nr_parts);
		if (_nr_parts>0) // to test if the user doesn't wants to remove all parts
		{
			float *temp = new float [_nr_parts];
			for (int i=0; i<_nr_parts; i++)
			{
				*(temp+i)=*(_parts+i); 
			}
			delete []_parts;
			_parts=temp;
		}
		else
		{
			cout<<"all parts have been removed"<<endl;
			delete []_parts;
			_parts=NULL;
		}
	}
	else
		cout<<"no Darray have pased"<<endl;
}

void Car::set_Car (int hp, float *parts,int nr_parts, const char *brandname)
{
	set_hp(hp);
	set_brandname(brandname);
	add_parts (parts,nr_parts);
	print_car();
}



void menu()
{
	cout << "choose .."<<endl;
	cout << "1 - Add part "<<endl;
	cout << "2 - remove parts "<<endl;

}


// get function
char Car::get_brandname ()const
{
	for (int i=0; i<strlen(_brandname); i++)
	{
		cout<<*(_brandname+i);
	}
	return 0;
}

int   Car::get_hp (void)const
{
	return _hp; 
}

//print function 
void Car::print_car()const
{
	cout <<"the name is :";
	cout<<get_brandname ();
	cout<<"\nwith ";
	cout<<get_hp ();
	cout<<" Hp."<<endl ;
	cout<<"Parts Details :"<<endl;
	for (int n =0; n<(_nr_parts); n++)
	{
		cout << " part Nr <"<<n+1<<"> cost :";
		cout << *(_parts+n)<<" Euro"<<endl;
	}
	
}

3rd Main

Code:

#include <iostream>
#include <stdlib.h>
#include "D_class.h"



using namespace std;

int main()
{
	char *names = NULL;
	int Hp=0;
	float *Part=NULL;
	int Nr_parts=0;
	int choose=0;
	char c='n';
	Car cars[3];
	


	

	for (int i=0; i<3; i++)
	{
		
		cout << "Enter Details for car Nr "<<i+1<<endl;
		cout << "1- Enter the name : ";
		names = new char[size];
		cin.get(names,size);
		clearBuf();

		cout << "2- Enter the Hp: ";
		cin >> Hp;
		cars[i].set_Car(Hp,Part,Nr_parts,names);
                                 if (names)
                                 delete[]names;
                                  names=NULL;

		/*i have stoped here ...... problem with the name;
		*/
	
	
	}

	return 0;
}

I think your problem is that when the user presses enter after inputting Hp, the '\n' stays in the stream. Adding cin.get(); after cin>>Hp; should fix the problem. That said, I think this is a better way to do what you want:

Code:

for (int i=0; i<3; i++)
{		
		cout << "Enter Details for car Nr "<<i+1<<endl;
		cout << "1- Enter the name : ";
		names = new char[size];
                         //cin.get will not extract the '\n' character
                         //so it is simply easier to use cin.getline
		cin.getline(names,size);
                         //no need for clearBuf() now 
		

		cout << "2- Enter the Hp: ";
		cin >> Hp;
		cin.get();//removes the '\n' (like clearBuf() did)
		cars[i].set_Car(Hp,Part,Nr_parts,names);
                                 if (names)
                                 delete[]names;
                                  names=NULL;


	
	}

Also see my previous post if you want to consider checking the input to make sure it didn't exceed the maximum size

hey JaWiB
thank you very much
you saved alot of my time ..... thank you again
it works