One-Stage and Two-Stage Construction of Objects
You have a choice between two techniques for creating graphic objects, such as pens and brushes:
One-stage construction: Construct and initialize the object in one stage, all with the constructor.
Two-stage construction: Construct and initialize the object in two separate stages. The constructor creates the object and an initialization function initializes it.
Two-stage construction is always safer. In one-stage construction, the constructor could throw an exception if you provide incorrect arguments or memory allocation fails. That problem is avoided by two-stage construction, although you do have to check for failure. In either case, destroying the object is the same process.
Примечание
These techniques apply to creating any objects, not just graphic objects.
Example of Both Construction Techniques
The following brief example shows both methods of constructing a pen object:
// One-stage
CPen myPen1(PS_DOT, 5, RGB(0,0,0));
// Two-stage: first construct the pen
CPen myPen2;
// Then initialize it
if(myPen2.CreatePen(PS_DOT, 5, RGB(0,0,0)))
{
// Use the pen
}