The Non-Virtual Interface idiom in D

[Andrei Alexandrescu]

Michel Fortin wrote:
> On 2009-09-26 10:06:24 -0400, Andrei Alexandrescu 
> <SeeWebsiteForEmail at erdani.org> said:
> 
>> Michel Fortin wrote:
>>> I think you're writing a lot of boilerplate code for something that 
>>> the compiler should be able to do by itself. I mean, it's a lot 
>>> cleaner with contracts, and there is no reason the compiler couldn't 
>>> generate itself that "contract-verifying" non-virtual function.
>>
>> I think it would be a mistake to latch on my quick examples. It's not 
>> only about before and after checks, it's more about low-level 
>> customization points versus higher-level interfaces.
> 
> Then your examples should have shown this instead.

Herb's article has them!

> I fully support having a way to specify a default implementation for a 
> function in an interface. It might get handy for a few things (like 
> implementing the delegate pattern you see everywhere in Cocoa). But it's 
> a bad replacement for contracts.

Walter has implemented contract inheritance, and we hope to be able to 
have contracts on interfaces in too. The former is a nice expected 
feature; the latter could convince DbC skeptics to start using it.

Andrei