[Dev-C++] help need for user-conversion operator problem

[bhadram r. <bha...@ya...>]

Dear friend,
              I'd a problem. I'm using user defined conversion function char* to use like 
char* ch=s1;(string object name); But the problem is that it is giving compilation error. It cannot able to find the conversion operator char*. Can any body solve my problem. Please help me in this aspect.I'd already defined user conversion operator. But still not working.
String::operator const char*() const
{
 return buf;
}
yours friendly,
bhadram
D:\cpppractice\aug20\maincpp.cpp(12) : error C2440: 'initializing' : cannot convert from 'class bhadram::String' to 'char *'
        No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called
Error executing cl.exe.
maincpp.obj - 1 error(s), 0 warning(s)

The program is as under:
cpp file is:
# include <iostream.h>
# include <String1.h>
using namespace bhadram;
void main()
{
 String s1("kummarasetti");
 String s2("veera");
 String s3("bhadram");
 char* ch=s1;
 cout<<ch;
 
 
 
}
header file:
# include <string.h>
namespace bhadram
{
class String
{
private:
 int size;
 char* buf;
 friend ostream& operator<<(ostream& ostr,String& s);
 friend istream& operator>>(istream& istr,String& s);
 friend String operator+(String ,String);
public:
 String(int n=0);
 String(const char* c);
 String(const String& s);
 String& operator=(String& s);
 String& operator+=(String& s);
 operator const char*() const;
};
String::operator const char*() const
{
 return buf;
}
String operator+(String s1,String s2)
{
 String tempOb;
 tempOb.size=s1.size+s2.size;
 tempOb.buf=new char[tempOb.size+1];
 strcpy(tempOb.buf,s1.buf);
 strcat(tempOb.buf,s2.buf);
 return tempOb;
}
String& String::operator+=(String& s)
{
 char* temp=new char[size+s.size+1];
 int tempSize=size+s.size;
 strcpy(temp,buf);
 strcat(temp,s.buf);
 delete [] buf;
 size=tempSize;
 buf=new char[tempSize+1];
 strcpy(buf,temp);
 return *this;
}

String& String::operator=(String& s)
{
 delete [] buf;
 size=s.size;
 buf=new char[size+1];
 strcpy(buf,s.buf);
 return *this;
 
}
istream& operator>>(istream& istr,String& s)
{
 delete [] s.buf;
 char tempBuffer[200];
 istr>>tempBuffer;
 s.size=strlen(tempBuffer);
 s.buf=new char[s.size+1];
 strcpy(s.buf,tempBuffer);
 return istr;
}
ostream& operator<<(ostream& ostr,String& s)
{
 return ostr<<s.buf;
}
String::String(const String& s)
{
 size=s.size;
 buf=new char[size+1];
 strcpy(buf,s.buf);
}
String::String(const char* c)
{
 size=strlen(c);
 buf=new char[size+1];
 for(int i=0;i<size;i++)
 {
  buf[i]=*c++;
 }
 buf[i]='\0';
}
String::String(int n)
{
 if(n==0)
  n=1;
 size=n;
 buf=new char[size+1];
 for(int i=0;i<n;i++)
 {
  buf[i]=' ';
 }
 buf[i]='\0';
}

};

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