Which derived class is it?

[Jeremy Cowles]

namespace Logic

Thats cool, but it is not what was described. Here is the solution that was
suggested:

namespace Logic
{
struct A { void draw( ) { } };
struct B : A { void draw( ) { } };
struct C : A { void draw( ) { } };
}


And this forces the logic to know how to draw, and my question is: isn't
this bad?


Jeremy

 

[Jarmo]

FAQ before posting. You can get the FAQ at:
http://www.parashift.com/cpp-faq-lite/

I think that should read http://www.parashift.com/c++-faq-lite/

 

[Jeffrey Schwab]

Thats cool, but it is not what was described. Here is the solution that was
suggested:

namespace Logic
{
struct A { void draw( ) { } };

Method "draw" should be virtual if {B,C}::draw are to override it.

struct B : A { void draw( ) { } };
struct C : A { void draw( ) { } };
}


And this forces the logic to know how to draw, and my question is: isn't
this bad?

It's "bad" in the sense that it's semantically ugly, and slightly less
efficient than the alternative I suggested.

-Jeff

 

[Jeremy Cowles]

Method "draw" should be virtual if {B,C}::draw are to override it.


It's "bad" in the sense that it's semantically ugly, and slightly less
efficient than the alternative I suggested.

Much more than symantically ugly, it is conceptually wrong. In order to
provide a different UI, you must redesign the classes or add a new draw
method - ie, it couples the business logic and the front-end. So I guess I
was just wondering if the designer knew something I don't.

Jeremy

 

[Jeffrey Schwab]

Much more than symantically ugly, it is conceptually wrong. In order to
provide a different UI, you must redesign the classes or add a new draw
method - ie, it couples the business logic and the front-end.

That doesn't make it "wrong," it's just monolithic. Lots of large
pieces of code have uglier couplings than this, but work well anyway for
a wide range of people. (Just ask any linux kernel or perl internals
developer.)

So I guess I
was just wondering if the designer knew something I don't.

I don't think so.