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.
.gif "Примечание") Примечание. |
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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
}