Classes and char* and Dynamic memory allocation

[Bozz]

Hello-

Can anyone please help?
THis code compiles fine and bombs just as sweet!

i tried debugging, and starting at this line:

CIS025String s3 = "Hello!";

i get ERROR cpString, expression cannot be evaluated.

Any thoughts most appreciated, thanks!


*************************************************

#include <iostream>


using namespace std;

class CIS025String{

private:
char *cpString; // Pointer to store the String Object ( Address of block of memory assigned for the string
// when the object is created).

public: CIS025String(); // Default Constructor
CIS025String(const char *cpS ); // Constructor
~CIS025String(); // Destructor

int GetLength();
int IsEmpty();

private: int CIS025String::GetSize(const char *cpS);

};

/********************
* Class CIS025String.
* Function Definitions
*
*
********************/



int main(){

CIS025String s3 = "Hello!"; // 7 Chars ( 6 chars + '\0' )



cout<< s3.IsEmpty();


return 0;

}

CIS025String::CIS025String(){ //Default Constructor

cout << "Using Default Constructor" << endl;

char *cpString = new char[1];
*cpString = 0;
}

CIS025String::CIS025String(const char* cpS){ // Constructor

cout << "Using Constructor" << endl;

int iLength = GetSize(cpS) + 1;

cout << "String Length = " << iLength-1 << endl;


char *cpString = new char[iLength];
*cpString = 0;

for( int i = 0; i < iLength; i++ ){
*(cpString+i) = *(cpS+i);
}
cout << cpString << endl; // Will output the String.

}
CIS025String::~CIS025String(){ //Destructor Declaration

delete [] cpString;
cpString = 0;
}
int CIS025String::GetSize(const char *cpS) {

int iLength = 0; // Character Counter

const char *ptr = 0;
ptr = cpS;

while(*ptr){
iLength++;
ptr++;
}
return iLength;
}
int CIS025String::GetLength() { //returns String Length (not inclusding terminating '\0'

int iLength = 0; // Character Counter

char *ptr = 0;
ptr = cpString;

while(*ptr){

iLength++;
ptr++;
}

return iLength;

}
int CIS025String::IsEmpty() {


char *ptr = 0;
ptr = cpString;
cout << *ptr;
if(!*ptr){

return 0;

}
else

return 1;

}
************************************************

[nextus]

can you use the cstring header file?

#include <cstring>

int x = strlen(pcharVar);
strcpy(pcharVar, pFromCharVar);

must simple...

[nextus]

found your problem!!!!!

you masked the class variable char *cpString with a local one

get rid of

char * cpString = new char[iLength];

// and put this
cpString = new char[iLength];

here is the working version of it

#include <iostream>



using namespace std;

class CIS025String{

private:
char *cpString; // Pointer to store the String Object ( Address of block of memory assigned for the string
// when the object is created).

public: CIS025String(); // Default Constructor
CIS025String(const char *cpS ); // Constructor
~CIS025String(); // Destructor

int GetLength(); 
int IsEmpty(); 

private: int CIS025String::GetSize(const char *cpS);

};

/********************
* Class CIS025String.
* Function Definitions
*
*
********************/



int main()
{
	CIS025String s3 = "Hello!"; // 7 Chars ( 6 chars + '\0' )

	cout<< s3.IsEmpty();

	return 0;

}

CIS025String::CIS025String() //Default Constructor
{
	cout << "Using Default Constructor" << endl;
	// doesn't need to allocate memory on the heap
}

CIS025String::CIS025String(const char* cpS) //Constructor
{

	cout << "Using Constructor" << endl;

	int iLength = GetSize(cpS) + 1; 


	cout << "String Length = " << iLength-1 << endl;

	char * cpString = new char[iLength];  

	for(int i = 0; i < iLength; i++ )
	{
		cpString[i] = cpS[i];
		//cout << cpS[i] << endl;
	}
	cout << cpString << endl; // Will output the String.

}
CIS025String::~CIS025String() //Destructor Declaration
{
	delete [] cpString;
	cpString = 0;
}
int CIS025String::GetSize(const char *cpS) 
{ 

	int iLength = 0; // Character Counter

	const char *ptr = cpS;

	while(*ptr)
	{
		iLength++;
		//cout << ptr << endl;
		ptr++;
	}	
	return iLength;
}
int CIS025String::GetLength() //returns String Length (not inclusding terminating '\0'
{

	int iLength = 0; // Character Counter

	char *ptr = 0;
	ptr = cpString;

	while(*ptr)
	{
		iLength++;
		ptr++;
	}

	return iLength;

}
int CIS025String::IsEmpty() 
{
	char *ptr = 0;
	ptr = cpString;
	cout << *ptr;
	if(!*ptr)
	{
		return 0;

	}
	else
	{
		return 1;
	}

}

i know it is syntax correct..but logically it doesnt work..so i fixed it... you're welcome

[Bozz]

Brilliant!!!
you are my hero-cant tell you how pleased this makes me.

It looks so obvious now, and my pc has stopped the BONG noise
If you are in Berkeley, CA i have to buy you a pint!

cheers,

bozz
Happy Coding