To give an example:

class Thread {
  ...
  Thread start() {...}
}

class Timer : Thread {
  ...
}


void main() {
  // Timer timer = new Timer().start;  // this does not work
  auto timer = new Timer().start; // because timer is of type Thread
}


thanks in advance,
christian

On 3/2/18 3:23 PM, Christian Köstlin wrote:
> To give an example:
> 
> class Thread {
>    ...
>    Thread start() {...}
> }
> 
> class Timer : Thread {
>    ...
> }
> 
> 
> void main() {
>    // Timer timer = new Timer().start;  // this does not work
>    auto timer = new Timer().start; // because timer is of type Thread
> }

Yes:

class Timer : Thread {
   override Timer start() { ... }
}

https://dlang.org/spec/function.html#virtual-functions

(see item 6)

-Steve

On 02.03.18 21:39, Steven Schveighoffer wrote:
> On 3/2/18 3:23 PM, Christian Köstlin wrote:
>> To give an example:
>>
>> class Thread {
>>    ...
>>    Thread start() {...}
>> }
>>
>> class Timer : Thread {
>>    ...
>> }
>>
>>
>> void main() {
>>    // Timer timer = new Timer().start;  // this does not work
>>    auto timer = new Timer().start; // because timer is of type Thread
>> }
> 
> Yes:
> 
> class Timer : Thread {
>    override Timer start() { ... }
> }
> 
> https://dlang.org/spec/function.html#virtual-functions
> 
> (see item 6)
> 
> -Steve
Thanks for this.
It works for me only without the override (with override I get
Error: function timer.Timer.start does not override any function, did
you mean to override 'core.thread.Thread.start'?).

Although I wonder if its possible to "fix" this in the Thread class with
some dlang magic. e.g. traits
class Thread {
  traits(GetClass) start() {...}
}

or perhaps

class ThreadHelper(T) : Thread {
  override T start() {return cast(T)super.start();}
}
class Timer : Thread!Timer {
}

>> class Timer : Thread {
>>    override Timer start() { ... }
>> }
>>
>> https://dlang.org/spec/function.html#virtual-functions
>>
>> (see item 6)
>>
>> -Steve
> Thanks for this.
> It works for me only without the override (with override I get
> Error: function timer.Timer.start does not override any function, did
> you mean to override 'core.thread.Thread.start'?).
This seems to be connected to Thread.start being a final function.

On Sat, Mar 03, 2018 at 01:13:43AM +0100, Christian Köstlin via Digitalmars-d-learn wrote:
> >> class Timer : Thread {
> >>    override Timer start() { ... }
> >> }
> >>
> >> https://dlang.org/spec/function.html#virtual-functions
> >>
> >> (see item 6)
> >>
> >> -Steve
> > Thanks for this.
> > It works for me only without the override (with override I get
> > Error: function timer.Timer.start does not override any function,
> > did you mean to override 'core.thread.Thread.start'?).
>
> This seems to be connected to Thread.start being a final function.

Well, yes, you cannot override a final function.  That is the point of `final`. :-D

If you meant to override it after all, remove the `final`.


T

-- 
Life is complex. It consists of real and imaginary parts. -- YHL

On 2018-03-02 21:23, Christian Köstlin wrote:
> To give an example:
>
> class Thread {
>    ...
>    Thread start() {...}
> }
>
> class Timer : Thread {
>    ...
> }
>
>
> void main() {
>    // Timer timer = new Timer().start;  // this does not work
>    auto timer = new Timer().start; // because timer is of type Thread
> }

You can also try a template this parameter [1] in the base class:

class Thread
{
    T start(this T) () { ... }
}

But if this "Thread" is core.thread.Thread that won't work.

[1] https://dlang.org/spec/template.html#template_this_parameter

-- 
/Jacob Carlborg