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digitalmars.D.learn - static member and/or property ?

reply chmike <christophe meessen.net> writes:
Sorry for the confusing subject, I couldn't find a concise 
formulation of my question.

I have a set of classes derived from the same interface so that I 
can use polymorphism.

I would like to store the name of the class as a string so that 
it can be retrieved as a static member of the class or by using 
polymorphism.

Here is the problem expressed as an exercise where you are 
invited to replace the ??? with the appropriate text, if it is 
possible. My blind and naive attempts failed.

interface AThing { ??? string name ??? }

class OneThing : AThing { ??? string name ??? "OneThing" ??? }

class OtherThing : AThing { ??? string name ??? "OtherThing" ??? }


void main()
{
    // Accessing name as static information
    writeln(OneThing.name ??? );

    // Accessing name through polymorphism
    AThing tbl;
    tbl ~= new OneThing;
    tbl ~= new OtherThing;
    tbl ~= new OneThing;
    foreach(a; tbl) writeln(a.name???);
}

The only viable solution I found so far is by using distinct 
member names. In the interface we define name as a property, and 
in the class we define the static member with another name. Is it 
possible to avoid the different names ?
May 19 2016
next sibling parent reply Edwin van Leeuwen <edder tkwsping.nl> writes:
On Thursday, 19 May 2016 at 15:04:00 UTC, chmike wrote:

 The only viable solution I found so far is by using distinct 
 member names. In the interface we define name as a property, 
 and in the class we define the static member with another name. 
 Is it possible to avoid the different names ?


Can you use identifier!(typeof(this)) or something along those 
lines. I am not sure how it behaves with inheritance.

https://dlang.org/spec/traits.html#identifier
May 19 2016
parent Edwin van Leeuwen <edder tkwsping.nl> writes:
On Thursday, 19 May 2016 at 15:12:44 UTC, Edwin van Leeuwen wrote:

 On Thursday, 19 May 2016 at 15:04:00 UTC, chmike wrote:

 The only viable solution I found so far is by using distinct 
 member names. In the interface we define name as a property, 
 and in the class we define the static member with another 
 name. Is it possible to avoid the different names ?


 Can you use identifier!(typeof(this)) or something along those 
 lines. I am not sure how it behaves with inheritance.

 https://dlang.org/spec/traits.html#identifier


Sorry I meant __traits(identifier, typeof(this)).
May 19 2016
prev sibling parent reply ag0aep6g <anonymous example.com> writes:
On 05/19/2016 05:04 PM, chmike wrote:

 interface AThing { ??? string name ??? }

 class OneThing : AThing { ??? string name ??? "OneThing" ??? }

 class OtherThing : AThing { ??? string name ??? "OtherThing" ??? }


 void main()
 {
     // Accessing name as static information
     writeln(OneThing.name ??? );

     // Accessing name through polymorphism
     AThing tbl;
     tbl ~= new OneThing;
     tbl ~= new OtherThing;
     tbl ~= new OneThing;
     foreach(a; tbl) writeln(a.name???);
 }

 The only viable solution I found so far is by using distinct member
 names. In the interface we define name as a property, and in the class
 we define the static member with another name. Is it possible to avoid
 the different names ?


Here's what I could come up with. I wouldn't be surprised if there was a 
simpler way to do it.

----
interface AThing
{
     final string name() { return nameImpl(); }
     string nameImpl();
}

class OneThing : AThing
{
     static string name() { return "OneThing"; }
     override string nameImpl() { return name(); }
}

class OtherThing : AThing
{
     static string name() { return "OtherThing"; }
     override string nameImpl() { return name(); }
}

void main()
{
    import std.stdio;

    // Accessing name as static information
    writeln(OneThing.name);

    // Accessing name through polymorphism
    AThing[] tbl;
    tbl ~= new OneThing;
    tbl ~= new OtherThing;
    tbl ~= new OneThing;
    foreach(a; tbl) writeln(a.name);
}
----

Can use a mixin template to reduce the boilerplate:

----
interface AThing
{
     final string name() { return nameImpl(); }
     string nameImpl();

     mixin template nameMixin()
     {
         static string name() { return typeof(this).stringof; }
         override string nameImpl() { return name(); }
     }
}

class OneThing : AThing { mixin AThing.nameMixin; }
class OtherThing : AThing { mixin AThing.nameMixin; }
----
May 19 2016
parent chmike <christophe meessen.net> writes:
On Thursday, 19 May 2016 at 15:33:21 UTC, ag0aep6g wrote:

 . . .
 interface AThing
 {
     final string name() { return nameImpl(); }
     string nameImpl();
 }

 class OneThing : AThing
 {
     static string name() { return "OneThing"; }
     override string nameImpl() { return name(); }
 }

 class OtherThing : AThing
 {
     static string name() { return "OtherThing"; }
     override string nameImpl() { return name(); }
 }


This is what I was looking fer. Thank you very much.

The fact that I used the class name is just a coincidence for 
making the example clear.
May 19 2016