• Satoshi (37/37) Apr 04 2017 Hi,
• Satoshi (11/11) Apr 04 2017 test/Foo.di(3,1): Error: class test.Foo.FooPrivate is forward
• Dejan Lekic (18/20) Apr 04 2017 Some parts of Phobos use it. Example:

Satoshi <satoshi rikarin.org> writes:

Hi,
do someone have any experience with pImpl and inheritance in D?

I tried something like:

// FooPrivate.d
class FooPrivate {
     int a;
}


// BarPrivate.d
import FooPivate;

class BarPrivate : FooPrivate {
     string b;
}


// Foo.d
import FooPrivate;

class Foo {
     protected FooPrivate m_private;

     this() { m_private = new FooPrivate; }
}


// Bar.d
import Foo;
import FooPrivate;
import BarPrivate;

class Bar : Foo {
     this() { m_private = new BarPrivate; }
}


And public interface
// Foo.di
class FooPrivate;
class Foo {
     private FooPrivate m_private;
}


Bar.d looks like it imported Foo with forward referenced 
FooPrivate and is unable to resolve it by importing FooPrivate.

Is this bug?
Do you know about any *less verbose* design pattern how I can 
hide implementaion details from .di files?

Thanks!

Satoshi <satoshi rikarin.org> writes:

test/Foo.di(3,1): Error: class test.Foo.FooPrivate is forward 
referenced when looking for 'opAssign'

forward reference in Foo.di


test/Bar.d(14,25): Error: cannot implicitly convert expression 
(p) of type test.BarPrivate.BarPrivate to test.Foo.FooPrivate

I'm unable to cast from BarPrivate to FooPrivate because it can't 
recognize Bar : Foo; inheritance from Foo.di (FooPrivate.d and 
BarPrivate.d is ignored).


test/Foo.di(3,1): Error: class test.Foo.FooPrivate is forward 
referenced when looking for 'opCast'

same as first

Dejan Lekic <dejan.lekic gmail.com> writes:

On Tuesday, 4 April 2017 at 12:05:15 UTC, Satoshi wrote:
 Hi,
 do someone have any experience with pImpl and inheritance in D?

Some parts of Phobos use it. Example: 
https://github.com/dlang/phobos/blob/master/std/stdio.d
Have a look at the struct ByLine

It has something like:

     struct ByLine(Char, Terminator)
     {
     private:
         import std.typecons : RefCounted, 
RefCountedAutoInitialize;

         /* Ref-counting stops the source range's Impl
          * from getting out of sync after the range is copied, 
e.g.
          * when accessing range.front, then using std.range.take,
          * then accessing range.front again. */
         alias PImpl = RefCounted!(Impl, 
RefCountedAutoInitialize.no);
         PImpl impl;