Misunderstanding in some if statements...

[Aceix]

What does this expression mean?

IDrawable *pDrawable = CreateTriangleShape();

if (pDrawable)
{
    pDrawable->Draw();
}

[guestgulkan]

Do you know how the if statement works?

[Aceix]

Yes, but what does the underlined part mean. Can you explain in pure English?

[guestgulkan]

it just checks if the pDrawable pointer is true or false - in C++ a non-zero value (for built in types) constitues true and a zero value is false.

so if pDrawable is non-zero (true) - it meant that the CreateTriangleShape() function returned a valid (non-zero) pointer
and the pDrawable->Draw() statement will be executed.

if CreateTriangleShape() could NOT create the triangle object it would return a zero value which would mean that if (pDrawable) would test as false and the pDrawable->Draw() statement would NOT be executed.

[Aceix]

Thank you very much. I now understand!!!

[Peter87]

Normally a zero pointer is called a null pointer. To make it more explicit the if statement could have been written in one of the following ways.

if (pDrawable != NULL)
if (pDrawable != 0)
if (pDrawable != nullptr)

[Aceix]

@Peter87

Yeah I know that one. Thanks!