C / C++ / MFC

hrishiS wrote:

I mean when do we use copy constructor and when assignment operator

Cedric Moonen wrote:

smarter "copy" mechanism (for instance your class contains a pointer which should be recreated instead of simply assigning the same address).

string var1 = "test";
string var2 = var1;
var2.replace(....);

int i;<br />
i = 10;

hrishiS wrote:

But could you please differentiate these with respect to shallow copy and deep copy?...and why we say so?

void ToStr(CString& val)
{
    val = "test";
}

void fun()
{
    CString val;
    ToStr(val);
}

hrishiS wrote:

the problem I could notice is that, ret is a automatic variable , so it is no longer available once it comes out from the function ToStr().

hrishiS wrote:

Either you can have it as global variable, or make a variable of pointer/reference of String , inside fun and pass it to ToStr

char* ToStr()
{
  return "test";
}

Cedric Moonen wrote:

If you return an object, the compiler will make a copy of it and assign it to val correctly.

char* ToStr()
{
  char buffer[5];
  lstrcpy(buffer, "test");
  return buffer;
}

Stuart Dootson wrote:

Part of the implied contract of ToStr is that callers will pass the address of a CString object

CString ToStr()
{
    CString ret = "test";
    return ret;
}

void fun()
{
    CString val = ToStr(); // it returns nothing (bad pointer)
}