digitalmars.D.learn - implimenting interface function by inheriting from other class

Alexey (25/25) Aug 21 2021 Hello

Bastiaan Veelo (14/39) Aug 21 2021 Not sure if this is the best way, but it does make dmd happy:

Alexey (3/47) Aug 21 2021 I want `this` inside of C1::coolFunc to return C2 if called as

Alexey (2/4) Aug 21 2021 so executing `cast(C2) this !is null` inside of C1::coolFunc

Alexey (50/54) Aug 21 2021 If this would work, I'd farther used this like so

Alexey (89/114) Aug 21 2021 we're with friends tried similar thing with c++, java, groovy and

Tejas (70/189) Aug 21 2021 Sorry, Bastiaan's solution is the only that I know of as well.

Alexey (2/27) Aug 22 2021 so, Is this a bug in dmd or not?

Alexey (4/36) Aug 22 2021 some answers have been given here and here

Alexey <invalid email.address> writes:

Hello
```D
interface Int
{
     void coolFunc();
}

class C1
{
     void coolFunc()
     {
         return;
     }
}

class C2 : C1, Int
{

}

void main()
{
     auto c = new C2;
}
```
dmd says it's not Ok:
t.d(14): Error: class `t.C2` interface function `void coolFunc()` 
is not implemented

how to make dmd happy?

Aug 21 2021

Bastiaan Veelo <Bastiaan Veelo.net> writes:

On Saturday, 21 August 2021 at 20:35:43 UTC, Alexey wrote:
 Hello
 ```D
 interface Int
 {
     void coolFunc();
 }

 class C1
 {
     void coolFunc()
     {
         return;
     }
 }

 class C2 : C1, Int
 {

 }

 void main()
 {
     auto c = new C2;
 }
 ```
 dmd says it's not Ok:
 t.d(14): Error: class `t.C2` interface function `void 
 coolFunc()` is not implemented

 how to make dmd happy?

Not sure if this is the best way, but it does make dmd happy: 
https://run.dlang.io/is/44F3AE

```d

class C2 : C1, Int
{
     override void coolFunc()
     {
         C1.coolFunc;
     }
}
```

It looks lame, I admit.

— Bastiaan.

Aug 21 2021

Alexey <invalid email.address> writes:

On Saturday, 21 August 2021 at 22:56:40 UTC, Bastiaan Veelo wrote:
 On Saturday, 21 August 2021 at 20:35:43 UTC, Alexey wrote:
 Hello
 ```D
 interface Int
 {
     void coolFunc();
 }

 class C1
 {
     void coolFunc()
     {
         return;
     }
 }

 class C2 : C1, Int
 {

 }

 void main()
 {
     auto c = new C2;
 }
 ```
 dmd says it's not Ok:
 t.d(14): Error: class `t.C2` interface function `void 
 coolFunc()` is not implemented

 how to make dmd happy?

 Not sure if this is the best way, but it does make dmd happy: 
 https://run.dlang.io/is/44F3AE

 ```d

 class C2 : C1, Int
 {
     override void coolFunc()
     {
         C1.coolFunc;
     }
 }
 ```

 It looks lame, I admit.

 — Bastiaan.

I want `this` inside of C1::coolFunc to return C2 if called as 
C2::coolFunc

Aug 21 2021

Alexey <invalid email.address> writes:

 I want `this` inside of C1::coolFunc to return C2 if called as 
 C2::coolFunc

so executing `cast(C2) this !is null` inside of C1::coolFunc 
would work

Aug 21 2021

Alexey <invalid email.address> writes:

On Saturday, 21 August 2021 at 23:14:14 UTC, Alexey wrote:
 I want `this` inside of C1::coolFunc to return C2 if called as 
 C2::coolFunc

 so executing `cast(C2) this !is null` inside of C1::coolFunc 
 would work

If this would work, I'd farther used this like so
```D
interface Int
{
     void coolFunc();
}

class C1
{
     void coolFunc()
     {
         {
             auto obj = (cast(C1)(cast(Int) this));
             if (obj !is null)
             {
                 do_one_thing();
             }
         }
         {
             auto obj = (cast(C2)(cast(Int) this));
             if (obj !is null)
             {
                 do_another_thing();
             }
         }
         {
             auto obj = (cast(C3)(cast(Int) this));
             if (obj !is null)
             {
                 do_something_else();
             }
         }
         return;
     }
}

class C2 : C1, Int
{

}

class C3 : C1, Int
{

}

class C4 : C1, Int
{

}

void main()
{
     auto c = new C2;
     c.coolFunc();
}

```

Aug 21 2021

Alexey <invalid email.address> writes:

On Saturday, 21 August 2021 at 20:35:43 UTC, Alexey wrote:
 Hello
 ```D
 interface Int
 {
     void coolFunc();
 }

 class C1
 {
     void coolFunc()
     {
         return;
     }
 }

 class C2 : C1, Int
 {

 }

 void main()
 {
     auto c = new C2;
 }
 ```
 dmd says it's not Ok:
 t.d(14): Error: class `t.C2` interface function `void 
 coolFunc()` is not implemented

 how to make dmd happy?

we're with friends tried similar thing with c++, java, groovy and 
go - worked ok.
```Java
interface Int
{
     public void coolFunc();
};

class C1
{
     public void coolFunc()
     {
         return;
     }
};

class C2 extends C1 implements Int
{

};


public class Main {

     public static void main(String args[])
     {
         Int c = new C2();
     }

}
```
```Groovy
interface Int
{
     void coolFunc()
}

class C1
{
     void coolFunc()
     {  print "hello" }
}

class C2 extends C1 implements Int
{ }

def printHello = { Int a -> a.coolFunc(); print " world: accept 
$Int" }

C2 a = new C2()
printHello(a)
```
```C++
class Int;
class C1;
class C2;

class Int
{
public:
     virtual void coolFunc() = delete;
};

class C1
{
public:
     virtual void coolFunc()
     {
         return;
     }
};

class C2 : public C1, public Int
{
public:
};

int main(int argc, char* argv[])
{
     auto c = new C2;
}
```
```Go
package main

import "fmt"

type Int interface {
   CoolFunc()
}

type C1 struct {
}

func (self *C1) CoolFunc() {
   fmt.Println("worked")
   return
}

type C2 struct {
   C1
}

func main() {

   var c Int

   c = new(C2)

   c.CoolFunc()

}
```

Aug 21 2021

Tejas <notrealemail gmail.com> writes:

On Sunday, 22 August 2021 at 01:14:08 UTC, Alexey wrote:
 On Saturday, 21 August 2021 at 20:35:43 UTC, Alexey wrote:
 Hello
 ```D
 interface Int
 {
     void coolFunc();
 }

 class C1
 {
     void coolFunc()
     {
         return;
     }
 }

 class C2 : C1, Int
 {

 }

 void main()
 {
     auto c = new C2;
 }
 ```
 dmd says it's not Ok:
 t.d(14): Error: class `t.C2` interface function `void 
 coolFunc()` is not implemented

 how to make dmd happy?

 we're with friends tried similar thing with c++, java, groovy 
 and go - worked ok.
 ```Java
 interface Int
 {
     public void coolFunc();
 };

 class C1
 {
     public void coolFunc()
     {
         return;
     }
 };

 class C2 extends C1 implements Int
 {

 };


 public class Main {

     public static void main(String args[])
     {
         Int c = new C2();
     }

 }
 ```
 ```Groovy
 interface Int
 {
     void coolFunc()
 }

 class C1
 {
     void coolFunc()
     {  print "hello" }
 }

 class C2 extends C1 implements Int
 { }

 def printHello = { Int a -> a.coolFunc(); print " world: accept 
 $Int" }

 C2 a = new C2()
 printHello(a)
 ```
 ```C++
 class Int;
 class C1;
 class C2;

 class Int
 {
 public:
     virtual void coolFunc() = delete;
 };

 class C1
 {
 public:
     virtual void coolFunc()
     {
         return;
     }
 };

 class C2 : public C1, public Int
 {
 public:
 };

 int main(int argc, char* argv[])
 {
     auto c = new C2;
 }
 ```
 ```Go
 package main

 import "fmt"

 type Int interface {
   CoolFunc()
 }

 type C1 struct {
 }

 func (self *C1) CoolFunc() {
   fmt.Println("worked")
   return
 }

 type C2 struct {
   C1
 }

 func main() {

   var c Int

   c = new(C2)

   c.CoolFunc()

 }
 ```

Sorry,  Bastiaan's solution is the only that I know of as well.

Here's your desired behaviour:

```d
import std.stdio:writeln;

interface Int
{
     void coolFunc();
}

class C1
{
     void coolFunc()
     {
         {
             auto obj = (cast(C1)(cast(Int) this));
             if (obj !is null)
             {
                 do_one_thing();
             }
         }
         {
             auto obj = (cast(C2)(cast(Int) this));
             if (obj !is null)
             {
                 obj.do_another_thing();
             }
         }
         {
             auto obj = (cast(C3)(cast(Int) this));
             if (obj !is null)
             {
                 obj.do_something_else();
             }
         }
         return;
     }

     void do_one_thing(){
         writeln("one thing from C1");
     }
}

class C2 : C1, Int
{
     override void coolFunc(){
         typeof(super).coolFunc();
     }

     void do_another_thing(){
         writeln("did another thing from C2");
     }

}

class C3 : C1, Int
{
     override void coolFunc(){
         typeof(super).coolFunc();
     }

     void do_something_else(){
         writeln("doing something else from C3");
     }

}

class C4 : C1, Int
{
     override void coolFunc(){
         typeof(super).coolFunc();
     }

}

void main()
{
     auto c = new C2;
     c.coolFunc();
}
```

Aug 21 2021

Alexey <invalid email.address> writes:

On Saturday, 21 August 2021 at 20:35:43 UTC, Alexey wrote:
 Hello
 ```D
 interface Int
 {
     void coolFunc();
 }

 class C1
 {
     void coolFunc()
     {
         return;
     }
 }

 class C2 : C1, Int
 {

 }

 void main()
 {
     auto c = new C2;
 }
 ```
 dmd says it's not Ok:
 t.d(14): Error: class `t.C2` interface function `void 
 coolFunc()` is not implemented

 how to make dmd happy?

so, Is this a bug in dmd or not?

Aug 22 2021

Alexey <invalid email.address> writes:

On Sunday, 22 August 2021 at 12:20:56 UTC, Alexey wrote:
 On Saturday, 21 August 2021 at 20:35:43 UTC, Alexey wrote:
 Hello
 ```D
 interface Int
 {
     void coolFunc();
 }

 class C1
 {
     void coolFunc()
     {
         return;
     }
 }

 class C2 : C1, Int
 {

 }

 void main()
 {
     auto c = new C2;
 }
 ```
 dmd says it's not Ok:
 t.d(14): Error: class `t.C2` interface function `void 
 coolFunc()` is not implemented

 how to make dmd happy?

 so, Is this a bug in dmd or not?

some answers have been given here and here
https://discord.com/channels/242094594181955585/242122752436338688/878996818904612864
https://issues.dlang.org/show_bug.cgi?id=22232

Aug 22 2021

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digitalmars.D.learn - implimenting interface function by inheriting from other class