Comments on: How to Turn a Hierarchy of Virtual Methods into a CRTP https://www.fluentcpp.com/2018/05/22/how-to-transform-a-hierarchy-of-virtual-methods-into-a-crtp/ Jonathan Boccara's blog Tue, 20 Nov 2018 07:27:54 +0000 hourly 1 https://wordpress.org/?v=6.5.3 By: Thief https://www.fluentcpp.com/2018/05/22/how-to-transform-a-hierarchy-of-virtual-methods-into-a-crtp/#comment-1078 Fri, 22 Jun 2018 10:44:00 +0000 https://www.fluentcpp.com/?p=2922#comment-1078 I would like to share some code of mine that allows for a class that supports CRTP to be used alone or derived from further: https://www.reddit.com/r/cpp/comments/8l8nw1/how_to_turn_a_hierarchy_of_virtual_methods_into_a/dzdr8fh/?context=2

template
class C : B<typename std::conditional<!std::is_same_v, derived, C>::type>;

Essentially if you use C, it will derive C from B<C>, but if you derive from C (e.g. D : C) then C will automatically derive from B instead of B<C>!

You could easily create a helper template which would only take derived and C as parameters and returned derived if non-void and C otherwise to simplify it. Something like:

template
using crtp_derive = std::conditional<!std::is_same_v, derived, class_name>::type;

template
class C : B<crtp_derive<derived, C>>;

maybe?

]]> By: NN https://www.fluentcpp.com/2018/05/22/how-to-transform-a-hierarchy-of-virtual-methods-into-a-crtp/#comment-1027 Thu, 31 May 2018 08:51:00 +0000 https://www.fluentcpp.com/?p=2922#comment-1027 CRTP and deep inheritance don’t play well if you don’t pass another parameter.
Better way is to do the following:

template
struct CRTP : base_t { // Use derived_t inside }

http://rsdn.org/forum/cpp/2674420.1

]]> By: Jonathan Boccara https://www.fluentcpp.com/2018/05/22/how-to-transform-a-hierarchy-of-virtual-methods-into-a-crtp/#comment-1013 Fri, 25 May 2018 10:51:00 +0000 https://www.fluentcpp.com/?p=2922#comment-1013 In reply to Simon NIVAULT.

Absolutely. I have worked your remark into the article, thank you very much Simon.

]]> By: Aymen Schehaider https://www.fluentcpp.com/2018/05/22/how-to-transform-a-hierarchy-of-virtual-methods-into-a-crtp/#comment-1009 Tue, 22 May 2018 10:01:00 +0000 https://www.fluentcpp.com/?p=2922#comment-1009 In reply to Simon NIVAULT.

I may agree with you Simon.

]]> By: Simon NIVAULT https://www.fluentcpp.com/2018/05/22/how-to-transform-a-hierarchy-of-virtual-methods-into-a-crtp/#comment-1008 Tue, 22 May 2018 07:37:00 +0000 https://www.fluentcpp.com/?p=2922#comment-1008 Hello Jonathan,

In your last solution, don’t you think we can make B inherit A instead of A<B> ?
If I so, I am not required to define the function helperfunction2 in the B body, and I think this work the same, don’t you ?

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