Comments on: 8.7 — The hidden “this” pointer http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/ Fri, 29 Aug 2008 19:48:30 +0000 http://wordpress.org/?v=2.5.1 By: Learn C++ - » 8.6 — Destructors http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/#comment-14393 Learn C++ - » 8.6 — Destructors Mon, 05 May 2008 01:56:44 +0000 http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/#comment-14393 [...] 2007 Prev/Next Posts « 8.5 — Constructors | Home | 8.7 — The hidden “this” pointer » Thursday, September 6th, 2007 at 9:14 [...] [...] 2007 Prev/Next Posts « 8.5 — Constructors | Home | 8.7 — The hidden “this” pointer » Thursday, September 6th, 2007 at 9:14 [...]

]]> By: Alex http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/#comment-10291 Alex Mon, 24 Mar 2008 22:20:48 +0000 http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/#comment-10291 I don't see anything syntactically wrong with that program, so without knowing what the error message was, I can't say. It is bizarre that you seem to have SetID() declared as a non-member function. Really it would be better if SetID() were declared as a member function, and then you could just say: <pre> cSimple.SetID(2); </pre> I don’t see anything syntactically wrong with that program, so without knowing what the error message was, I can’t say. It is bizarre that you seem to have SetID() declared as a non-member function. Really it would be better if SetID() were declared as a member function, and then you could just say:

cSimple.SetID(2);
]]> By: emre http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/#comment-10186 emre Sun, 23 Mar 2008 11:36:51 +0000 http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/#comment-10186 I tried this but didn't work , why ? <pre> int main() { Simple cSimple(1); SetID(&cSimple,2); std::cout << cSimple.GetID() << std::endl; } I tried this but didn’t work , why ?

int main()
{
    Simple cSimple(1);
    SetID(&cSimple,2);
    std::cout << cSimple.GetID() << std::endl;
}
]]> By: Zafer http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/#comment-7278 Zafer Tue, 05 Feb 2008 13:07:43 +0000 http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/#comment-7278 Ok thanks. Ok thanks.

]]> By: Alex http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/#comment-7256 Alex Tue, 05 Feb 2008 03:31:37 +0000 http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/#comment-7256 As you note, the "this" pointer can contain different addresses so it can point to different objects. This does not violate the fact that the *this pointer is const. All the const means is that we can not change what the *this pointer points to when we're inside the function. The const does not restrict what we set the pointer to in the first place! For example, consider the following function: <pre> int PrintValue(const int nValue) { // We can not change the value of nValue inside the function! cout << nValue; } int main() { // However, we can set nValue to whatever we want // when we call the function! PrintValue(4); PrintValue(6); } </pre> This program is pretty straightforward. The first time we call PrintValue, we set nValue to 4. The second time we set it to 6. The *this pointer works exactly like this, except that it's type is "X* const" instead of int (where X is the name of the class the non-static member function belongs to), and the compiler automatically sets it's value based on the object we're calling the function on. As you note, the “this” pointer can contain different addresses so it can point to different objects. This does not violate the fact that the *this pointer is const. All the const means is that we can not change what the *this pointer points to when we’re inside the function. The const does not restrict what we set the pointer to in the first place!

For example, consider the following function:

int PrintValue(const int nValue)
{
    // We can not change the value of nValue inside the function!
    cout < < nValue;
}

int main()
{
    // However, we can set nValue to whatever we want
    // when we call the function!
    PrintValue(4);
    PrintValue(6);
}

This program is pretty straightforward. The first time we call PrintValue, we set nValue to 4. The second time we set it to 6.

The *this pointer works exactly like this, except that it’s type is “X* const” instead of int (where X is the name of the class the non-static member function belongs to), and the compiler automatically sets it’s value based on the object we’re calling the function on. ]]> By: Zafer http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/#comment-7249 Zafer Tue, 05 Feb 2008 02:03:02 +0000 http://www.learncpp.com/cpp-tutorial/87-the-hidden-this-pointer/#comment-7249 As a pointer, "this" contains the memory address of a class object. However, since we can call a class function from different objects, "this" pointer should be able to contain different addresses so that it can point to different objects. How does this happen when "this" is a const pointer? As a pointer, “this” contains the memory address of a class object. However, since we can call a class function from different objects, “this” pointer should be able to contain different addresses so that it can point to different objects. How does this happen when “this” is a const pointer?

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