Re: Correct vesion (Re: Clone an object with an abstract base class)
JiiPee wrote:
On 12/10/2014 01:20, Mr Flibble wrote:
On 12/10/2014 01:18, Mr Flibble wrote:
On 12/10/2014 00:55, JiiPee wrote:
On 12/10/2014 00:26, JiiPee wrote:
How about checking the type of the *b object first and creating that
type of object:
void f2(B *b) {
B *b1 = nullptr;
if( typeid(*b).name() == typeid(D1).name() )
b1 = new D1(*b1); // *b is type D1
else if( typeid(*b).name() == typeid(D2).name() )
b1 = new D2(*b1); // *b is type D2
}
and maybe also *b1 must be converted to its type like:
new D1( *((D1*)b1) )
?
this is better and compiles:
void f2(B *b) {
B *b1 = nullptr;
if( typeid(*b).name() == typeid(D1).name() )
b1 = new D1(*(reinterpret_cast<D1*>(b1)));
else if( typeid(*b).name() == typeid(D2).name() )
b1 = new D2(*(reinterpret_cast<D2*>(b1)));
}
You should use static_cast not reinterpret_cast when casting from base
to derived.
Of course your solution doesn't scale: what if b points to an object
derived from D1?
Much better solution is to have a pure virtual clone() method.
/Flibble
Then that new derived class should be added, so one if- more. But this
is also the case if more classes are derived from from B; they all need
to have their own if-block.
Why is that better than a clone method?
--
Ian Collins