C / C++ / MFC

<code>// In the header file
class CMot
{
// Stuff goes here
     CMot& operator = (const CMot);
// Stuff goes here
}
 
// In the C++ file
CMot& CMot::operator = (const CMot m)
{
     return m;
}

class CMot
{
   CMot & operator = (const CMot &);
};

CMot &CMot::operator = (const CMot &m)
{
   this->member_variable = m.member_variable;
   return *this;
}

(mot1 = mot2) = mot3;

int x, y, z;
x=y=z=1;

x = (y = (z = 1));

((x = y) = z) = 1;

int iValue = 3;
int* pValue = &iValue; // pointer to value
*pValue = 4;
int& rValue = &iValue; // reference to value
rValue = 5;

struct Point{
int x;
int y;
};

void FunctionA(Point ptMouse)
{
  ptMouse.x = 100;
}

void FunctionB(Point* pMouse)
{
  pMouse->x = 100;
}

void FunctionC(Point& rMouse)
{
  rMouse.x = 100;
}

<br />
CClientDC dc(this);<br />
<br />
CPen penBlue = new CPen();<br />
penBlue.Create(PS_SOLID,1,RGB(0,0,255));<br />
<br />
dc.SelectObject(penBlue) // pass by value, makes a copy - uses up a lot of memory (BAD)<br />
<br />
//instead use<br />
<br />
dc.SelectObject(&penBlue) // pass by address - fast and effecient, using original object (GOOD)<br />
<br />
also you could use<br />
<br />
CPen& rPenBlue = &penBlue;<br />
dc.SelectObject(rPenBlue) // not sure if this is right but pass by reference<br />
<br />

Tom Moore wrote:

CClientDC dc(this);

CPen penBlue = new CPen();
penBlue.Create(PS_SOLID,1,RGB(0,0,255));

dc.SelectObject(penBlue) // pass by value, makes a copy - uses up a lot of memory (BAD)

<br />
CClient* pDC(this);<br />
CPen penRed = new CPen()<br />
<br />
penRed.Create(PS_SOLID,1,RGB(255,0,0); // Create a solid red pen<br />
<br />
CPen penOld = dc->SelectObject(&penRed); // Select the red pen and store the old pen in // penOld, but why use the address of it?<br />
<br />
dc.DrawText(300,400,penRed,"Hello World"); // Print Hello World<br />
<br />
dc.SelectObject(penOld) //Select the old object using the pointer<br />

<br />
 CRect rc;<br />
 GetWindowRect(&rc);<br />

CClient* pDC(this);
CPen *penRed = new CPen();

penRed->Create(PS_SOLID,1,RGB(255,0,0)); // Create a solid red pen

CPen *penOld = dc->SelectObject(penRed); // Select the red pen and store the old pen in // penOld, but why use the address of it?

//dc.DrawText(300,400,penRed,"Hello World"); // Print Hello World

dc.SelectObject(penOld) //Select the old object using the pointer

Tom Moore wrote:

Whats the difference between :

GetWindowRect(&rc); and

GetWindowRect(rc);

// pass-by-value
void foo( int num )
{
    num = 12;
}
...
int x = 5;
printf("%x\n", x); // will print 5
foo(x);
printf("%x\n", x); // will also print 5
 
// pass-by-reference
void foo( int *num )
{
    *num = 12; // change the value pointed to by 'num'
}
...
int x = 5;
printf("%x\n", x); // will print 5
foo(&x);
printf("%x\n", x); // will now print 12

"Let us be thankful for the fools. But for them the rest of us could not succeed." - Mark Twain

"There is no death, only a change of worlds." - Native American Proverb