A question on multiple-inheritance and its usefullness

[mike]

Hello fellow C++ experts,
is there any dramatic difference between multiple inheritance:

struct MyType4 : MyType1, MyType2, MyType3 {
int MyInt;
};

and:

struct MyType4 {
MyType1 MyObject1;
MyType2 MyObject2;
MyType3 MyObject3;
int MyInt;
};

?

Is just neat sintactic sugar, or is there something that is impossible
to be achieved with the 2nd solution?

I mean, a function accepting a pointer to MyType2 can accept also a
pointer to a MyType4 object, and that's neat, but I could always pass
&MyObject4.MyOb ject2 to that function (2nd solution without multiple
inheritance), producing the same result (at least I think). Hence my
question "Is just neat sintactic sugar, or..".

Thanks,
Mike

[mlimber]

mi**@nospam.com wrote:

Hello fellow C++ experts,
is there any dramatic difference between multiple inheritance:

struct MyType4 : MyType1, MyType2, MyType3 {
int MyInt;
};

and:

struct MyType4 {
MyType1 MyObject1;
MyType2 MyObject2;
MyType3 MyObject3;
int MyInt;
};

?

Is just neat sintactic sugar, or is there something that is impossible
to be achieved with the 2nd solution?

I mean, a function accepting a pointer to MyType2 can accept also a
pointer to a MyType4 object, and that's neat, but I could always pass
&MyObject4.MyOb ject2 to that function (2nd solution without multiple
inheritance), producing the same result (at least I think). Hence my
question "Is just neat sintactic sugar, or..".

You can't implement virtual functions for MyTypes 1-3 in MyType4
without inheritance. Check out:

http://www.parashift.com/c++-faq-lit....html#faq-25.4

Cheers! --M

[mlimber]

mlimber wrote:

mi**@nospam.com wrote:

Hello fellow C++ experts,
is there any dramatic difference between multiple inheritance:

struct MyType4 : MyType1, MyType2, MyType3 {
int MyInt;
};

and:

struct MyType4 {
MyType1 MyObject1;
MyType2 MyObject2;
MyType3 MyObject3;
int MyInt;
};

?

Is just neat sintactic sugar, or is there something that is impossible
to be achieved with the 2nd solution?

I mean, a function accepting a pointer to MyType2 can accept also a
pointer to a MyType4 object, and that's neat, but I could always pass
&MyObject4.MyOb ject2 to that function (2nd solution without multiple
inheritance), producing the same result (at least I think). Hence my
question "Is just neat sintactic sugar, or..".

You can't implement virtual functions for MyTypes 1-3 in MyType4
without inheritance. Check out:

http://www.parashift.com/c++-faq-lit....html#faq-25.4

See also FAQs 24.2 and 24.3.

Cheers! --M