Nesting classes is strange to me in Dlang because it adds a parent pointer to the parent class. I don't see the point of this and it seems like an anti-feature. If we wanting that pattern we could implement it ourselves. I suppose in some cases it can be useful but in my case it breaks logical nesting.

I have two classes A and B. I want B to look like it is derived or a member of A.

So I want to do A.B when accessing B to explicitly signal that B is from A.

e.g.,

class A { class B { ...

BUT I do not want class B to be physically connecting to A. I would like to instantiate it outside of A. I can't do this in Dlang. Regardless of why I want to do this, the fact remains that I can't do it in Dlang. So, the question is, how can I still get the logical behavior? I've tried to put B in a module A, but this doesn't seem to work.


In fact, I'm programming from interfaces,

interface A { interface B { ...

class C : A { class D : A.B { ...

So I have for D, analogous to A.B, C.D.

D will never be used, I think outside of D, except when inheriting from D to create polymorphic behavior... direct injection will be used along with factories and requiring D to be a physical child of D will just be a pain in the ass(requiring all of C to be implemented I think).

Basically, D will never access the parent(they are just wrappers around tight objects. So I don't need the parent pointer, yet I'm forced to do so.

JS:

> the fact remains that I can't do it in Dlang.

Is tagging the inner class as static helping?

class A {
    static class B { ... }
}

Bye,
bearophile

On Friday, 2 August 2013 at 11:47:46 UTC, bearophile wrote:
> JS:
>
>> the fact remains that I can't do it in Dlang.
>
> Is tagging the inner class as static helping?
>
> class A {
>     static class B { ... }
> }
>
> Bye,
> bearophile

Just to be clear, marking the inner class as static means that B will not have a pointer to A. It is the same as defining B outside A, the difference being that B is not visible to anything outside the module.

On Friday, 2 August 2013 at 12:29:02 UTC, Meta wrote:
> On Friday, 2 August 2013 at 11:47:46 UTC, bearophile wrote:
>> JS:
>>
>>> the fact remains that I can't do it in Dlang.
>>
>> Is tagging the inner class as static helping?
>>
>> class A {
>>    static class B { ... }
>> }
>>
>> Bye,
>> bearophile
>
> Just to be clear, marking the inner class as static means that B will not have a pointer to A. It is the same as defining B outside A, the difference being that B is not visible to anything outside the module.

Then that doesn't help. Do you mean A.B is not visible outside the module either? Can B be instantiated and inherited when static, if not then it is no use.

To be. clear I want B to behave like any ordinary "root" class(just like A), except I want to have to access it through A(logically). This creates a hierarchical way of accessing types that makes it clear how they are related to other types, but doesn't prevent them from being used in a non-hierarchical way if necessary(The way D deals with nested classes prevents this).

On Friday, 2 August 2013 at 13:37:09 UTC, JS wrote:
> Then that doesn't help. Do you mean A.B is not visible outside the module either? Can B be instantiated and inherited when static, if not then it is no use.

Yes, A will act simply as a "namespace". If B is public, it can be accessed and instantiated from other modules. All static does here is removing hidden context pointer.

On Friday, 2 August 2013 at 13:57:08 UTC, Dicebot wrote:
> On Friday, 2 August 2013 at 13:37:09 UTC, JS wrote:
>> Then that doesn't help. Do you mean A.B is not visible outside the module either? Can B be instantiated and inherited when static, if not then it is no use.
>
> Yes, A will act simply as a "namespace". If B is public, it can be accessed and instantiated from other modules. All static does here is removing hidden context pointer.

ok, then that is exactly what I want.

Thanks.

On Friday, 2 August 2013 at 13:57:08 UTC, Dicebot wrote:
> On Friday, 2 August 2013 at 13:37:09 UTC, JS wrote:
>> Then that doesn't help. Do you mean A.B is not visible outside the module either? Can B be instantiated and inherited when static, if not then it is no use.
>
> Yes, A will act simply as a "namespace". If B is public, it can be accessed and instantiated from other modules. All static does here is removing hidden context pointer.

Sorry to hijack the question, but this is relevant to the OP. I can't remember; are class member public or private by default?

On Friday, 2 August 2013 at 17:16:21 UTC, Meta wrote:
> Sorry to hijack the question, but this is relevant to the OP. I can't remember; are class member public or private by default?

Public by default.