Re: convert "class of" in pascal to D.

[rumbu]

On Wednesday, 30 January 2013 at 14:48:07 UTC, Eko Wahyudin wrote:

Hi, guys? I'm new in D and I come from pascal. The constructor
concept is very different, and it's very confusing for me.

I want to create some statement in D which in pascal like this.

type
     TMyObjectAClass = class of TMyObject_A;   // number 1

     TMyObject_A = class
        constructor Create(AString : String);
     end;

     TMyObject_B = class(TMyObject_A)
        constructor Create(AString : String); override;
     end;

     TMyObject_C = class(TMyObject_A)
     end;
- - - - - - - - - - - - - - - - -

function Foo(AClass: TMyObjectAClass): TMyObject_A;
begin
    Result:= AClass.Create(AClass.ClassName);  //number 2
end;

- - - - - - - - - - - - - - - - -
var
    B : TMyObject_B;
    C : TMyObject_C;
begin
    B:= Foo(TMyObject_B);  //number 3
    C:= Foo(TMyObject_C);
end.

===================================================================
Question 1> How I can make a data type "class of" in D language
Question 2> How to convert number 2, in D language.
Question 3> How I passing a "class type" as argument like number

3, and if D can do same thing like pascal, which one is called by

D, TMyObject_A.Create() or TMyObject_B.Create() ? In pascal It
should be call TMyObject_B.Create() first

Thanks :)
Eko

There are no class types in D and classes without empty
constructors cannot be instantiated directly.

The closest solution is to use a templated function for Foo:

class TMyObject_A
{
     this(string AString)
        { }
}

class TMyObject_B : TMyObject_A
{
     this(string AString) { super(AString); }
}

class TMyObject_C : TMyObject_A
{
     this(string AString) { super(AString); }
     //there is no default constructor without parameters in the
base class.
}

TMyObjectAClass Foo(TMyObjectAClass)() if (is(TMyObjectAClass :
TMyObject_A))
{
        return new TMyObjectAClass(TMyObjectAClass.stringof);
}


int main(string[] argv)
{
        TMyObject_B B = Foo!TMyObject_B();
        TMyObject_C C = Foo!TMyObject_C();

    return 0;
}