Re: Create objects

James Kanze <>
Wed, 11 Mar 2009 02:19:39 -0700 (PDT)
On Mar 10, 2:57 pm, SG <> wrote:

On 10 Mrz., 13:32, "" <> wrote:

On Mar 9, 5:15 pm, Anarki <> wrote:

Is there a way to create an object by just knowing its type?

Here's just another suggestion: You could try to combine the
envelope/ letter idiom with the factory pattern in your case.
The "envelope" makes it easier to manage the polymorphic
object's life-time.

The envelope/letter pattern is designed so that polymorphic
objects can have value semantics. It's rarely needed, and has
considerable overhead.

In C++, there is no solution for arbitrary types: I would
consider this a feature, however, and not a defect. If all of
the types in question derive from a common base class, it is
rather simple to use a std::map< std::string, Base* (*)() > to
map names to a factory function. (If the types are not
necessarily all known at compile time, it's also possible to
define a mapping type name to filename, with the corresponding
file being dynamically linked in if the name isn't found in the
map. The types still have to derive from a common base,
however, to be useful.)

James Kanze (GABI Software)
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