• John Colvin (3/3) May 16 2020 What's the best way to implement an Objective C protocol in D?
• John Colvin (6/9) May 17 2020 Based on some experimentation, I'm starting to wonder do
• Jacob Carlborg (31/41) May 17 2020 No, not really.
• Guillaume Piolat (5/8) May 17 2020 I did it throught the Obj-C runtime a while ago:

John Colvin <john.loughran.colvin gmail.com> writes:

What's the best way to implement an Objective C protocol in D?

I see mention here 
https://dlang.org/changelog/2.085.0.html#4_deprecated_objc_interfaces but it's
not clear where things are these days.

John Colvin <john.loughran.colvin gmail.com> writes:

On Saturday, 16 May 2020 at 19:14:51 UTC, John Colvin wrote:
 What's the best way to implement an Objective C protocol in D?

 I see mention here 
 https://dlang.org/changelog/2.085.0.html#4_deprecated_objc_interfaces but it's
not clear where things are these days.

Based on some experimentation, I'm starting to wonder do 
protocols actually have any runtime component in Objective C? 
Because if I pass in an extern(Objective-C) class with the right 
interface to a function expecting a protocol everything just 
works.

Jacob Carlborg <doob me.com> writes:

On 2020-05-17 11:32, John Colvin wrote:
 On Saturday, 16 May 2020 at 19:14:51 UTC, John Colvin wrote:
 What's the best way to implement an Objective C protocol in D?

 I see mention here 
 https://dlang.org/changelog/2.085.0.html#4_deprecated_objc_interfaces 
 but it's not clear where things are these days.


It's the same these days. It's still not implemented.

 Based on some experimentation, I'm starting to wonder do protocols 
 actually have any runtime component in Objective C?

No, not really.

 Because if I pass in  an extern(Objective-C) class with the right interface to
a function 
 expecting a protocol everything just works.

Yes, that works fine.

You can put the methods from the protocol directly in the class that 
implements them or in a base class. If you really want to have a 
specific type for the protocol you can use an abstract class to emulate 
an interface/protocol and cast your actual class to the abstract class:

extern (Objective-C)
abstract class Printer // the protocol
{
     void print(int value)  selector("print:");
}

extern (Objective-C)
class Foo : NSObject
{
     override static Foo alloc()  selector("alloc");
     override Foo init()  selector("init");

     void print(int value)  selector("print:")
     {
         writeln(value);
     }
}

extern (Objective-C) void print(Printer);

void main()
{
     auto foo = Foo.alloc.init;
     print(cast(Printer) cast(void*) foo); // need to cast through void*
}

-- 
/Jacob Carlborg

Guillaume Piolat <firstname.lastname gmail.com> writes:

On Saturday, 16 May 2020 at 19:14:51 UTC, John Colvin wrote:
 What's the best way to implement an Objective C protocol in D?

 I see mention here 
 https://dlang.org/changelog/2.085.0.html#4_deprecated_objc_interfaces but it's
not clear where things are these days.

I did it throught the Obj-C runtime a while ago:
https://github.com/AuburnSounds/Dplug/blob/dda1f80d69e8bfd4af0271721738ce827c2f0eae/au/dplug/au/cocoaviewfactory.d#L99

and the result is brittle, you need to replicate the protocol 
declaration, add all methods etc.