Getters/setters generator

[Mark via Digitalmars-d-announce]

On Tuesday, 17 January 2017 at 15:59:26 UTC, Andrei Alexandrescu 
wrote:
> On 1/17/17 12:08 PM, Mark wrote:
>> On Tuesday, 17 January 2017 at 09:17:56 UTC, Andrei 
>> Alexandrescu wrote:
>>> On 1/17/17 9:32 AM, Eugene Wissner wrote:
>>>> Ah, well thanks. I don't think it makes much sense since it 
>>>> would be
>>>> easier to write a complete setter if the user needs extra 
>>>> checks.
>>>> Accessors are there only for the generation of the standard 
>>>> methods,
>>>> that just get or set some object property.
>>>
>>> Hmmm... that's a bit of a bummer because it helps only the 
>>> degenerate
>>> case (accessors are there as placeholders for future 
>>> extensions, and
>>> otherwise offer no protection whatsoever compared to a public 
>>> value).
>>> The question would be then what would be use cases for the 
>>> accessors.
>>> Predicated setters are not just a random thing one might want 
>>> out of
>>> many possibilities, it's a frequent pattern. -- Andrei
>>
>> Given that D supports class invariants, is there a real need 
>> for
>> predicated setters?
>
> The invariant is evaluated after the setter has taken place, 
> i.e. after the object has been corrupted. The setter guard 
> prevents corruption from happening.  -- Andrei

I see. Is there a way to call invariant() of a class/struct 
directly? That would obviate the need for a particular predicate 
(copy the class state, run the setter, check if invariants are 
satisfied and restore previous state if they aren't).