Is there a drop-dead simple way to clone an object?

I've got a small tree of classes (tBaseProfile, and four descendants of such). Only the descendant classes are instantiated. I need to be able to create new copies of these objects for use in other lists.

At the moment, I am writing a Duplicate method that returns the new object. But this means assigning all of the data to the duplicated object. There must be an easier way!

2014-03-19 19:01 GMT-03:00 Timothy Groves :

I'm working on something right now (using RTTI). I need to clone any object, even third party objects. I use an OPF and a HTTP framework and both work directly with objects, and now came the need to clone objects ( http://goo.gl/VVTFcu).

I'll post the code here soon ...

Timothy Groves wrote

Is there a drop-dead simple way to clone an object?

The convention established in Delphi for TPersistent descendants is to provide an Assign method to do this, so for TPersistent descendants (components, controls etc.) you can just override this method. I know of no such method provided above TPersistent in the TObject hierarchy.

There is usually a good reason to NOT do it blindly for all members and why you don't find a default "clone" method in any programming language in can think of right now.

Just think about it: you clone a database object (from an ORM or similar). How far does the clone/copy go? Will you also clone the associated database connection object? Probably not, so your manual code would only assign the same reference to the clone. However the table name, field name, sql statement etc. will be copied.

Or think about file access: your object has a TFileStream as member. Will you clone that? What if the access was read/write and maybe even exclusive?

IMHO there is no one-size-fits-all here.

Best regards,
Andreas

Timothy Groves wrote

Is there a drop-dead simple way to clone an object?

AFAIK, there are good reasons, why any class needs to implement it's own dedicated "assign" method to be cloneable.

-Michael