Is it good practice to pass scoped_ptr by reference (from one method to another inside a class)?

Question

Or if i need to do that, then i should just use shared_ptr?

I know i have many questions regarding smart pointer - i still don't quite understand when to use which smart pointer.

Answer 1

Yes you can pass it by reference.

However, if the function just wants to use the managed object, you might consider passing a reference to the object itself.

void foo(const boost::scoped_ptr<Object>& o)
{
     o->foobar();
}

void bar(const Object& o)
{
     o.foobar();
}

The difference is that in the first case you have coupled the function with a particular smart pointer type.

Object o;
boost::scoped_ptr<Object> scoped(new Object);
boost::shared_ptr<Object> shared(new Object);

foo(o);  //no
foo(scoped); //OK
foo(shared); //no

bar(o);  //OK
bar(*scoped); //OK
bar(*shared); //OK

Generally I'd only pass the scoped_ptr, if the intention is to do something with the scoped_ptr instance itself (e.g release or reset the resource). Similarly for shared_ptr (e.g the function wants to share the resource with other shared pointers).