Thread overview
how to test (at compilation-time) for existence of an already-declared object ?
Jul 24
someone
Jul 24
someone
July 24

Suppose I have a module with the following:

public class classTickerCustomNYSE : classTickerCommon { ... }
public class classTickerCustomNASDAQ : classTickerCommon { ... }

... and given that I also have the following in the same module:

public enum structureExchanges = [
   r"NYSE"d   : structureExchange(r"NYSE"d, r"New York Stock Exchange"d, r"USD"d, r"usa"d, r"New York"d, r"EST"d),
   r"NASDAQ"d : structureExchange(r"NASDAQ"d, r"National Association of Securities Dealers Automated Quotations"d, r"USD"d, r"usa"d, r"New York"d, r"EST"d),
   r"LSE"d    : structureExchange(r"LSE"d, r"London Stock Exchange"d, r"GBP"d, r"gbr"d, r"London"d, r"UTC"d),
   r"XETRA"d  : structureExchange(r"XETRA"d, r"Deutsche Börse"d, r"EUR"d, r"deu"d, r"Frankfurt am Main"d, r"CET"d),
   r"B3"d     : structureExchange(r"B3"d, r"B3 formerly Bolsa de Valores de São Paulo (aka BOVESPA)"d, r"BRL"d, r"bra"d, r"São Paulo"d, r"BRT"d),
   r"BCBA"d   : structureExchange(r"BCBA"d, r"Bolsa de Comercio de Buenos Aires"d, r"ARS"d, r"arg"d, r"Buenos Aires"d, r"ART"d)
   ];

public struct structureExchange { /// solely‐intended to help build code at compilation‐time; for client‐code classExchanges should be used instead

   public dstring ID;
   public dstring name;
   public dstring currencyID;
   public typeLocation location;

   @safe this(
      const dstring lstrExchangeID,
      const dstring lstrExchangeName,
      const dstring lstrCurrencyID,
      const dstring lstrCountryID,
      const dstring lstrCity,
      const dstring lstrTZ
      ) {

      ID = lstrExchangeID;
      name = lstrExchangeName;

      currencyID = lstrCurrencyID;

      location = typeLocation(
         lstrCountryID,
         lstrCity,
         lstrTZ)
         ;

   }

}

... at compilation-time I can do things like:

static foreach (structureExchange sudtExchange; structureExchanges) { /// assume the following code as a template to build new classTickerCustom{ExchangeID} classes

   mixin(format!

      ` /// code chunk

      final public class classTickerCustom%1$s : classTickerCommon {

      ...

      }

      `(sudtExchange.ID) /// code chunk

   ); /// mixin ending

}

... now, question is: how can I check, within the static foreach code, whether a class is already-implemented or not; eg:


static foreach (structureExchange sudtExchange; structureExchanges) {

   if (! ? == r"classTickerCustom"d ~ sudtExchange.ID) {

      /// class is not implemented yet: do whatever here ...

   }

}

... my first thought was traits (https://dlang.org/spec/traits.html) but I don't see anything useful there; there is getMember() but the example is for already-declared objects within the module, and not the module itself.

July 24

On Saturday, 24 July 2021 at 01:29:26 UTC, someone wrote:

>

Suppose I have a module with the following:

static if(is(classTickerCustomNYSE))
// it was a valid type
else
// it was not a valid type

can use that to test. you can also mix in the name

static if(is(mixin("class name here"))) {}

There's similar tricks for testing for imports and such too but i recommend here you import the module first then can test it.

July 24

On Saturday, 24 July 2021 at 01:44:11 UTC, Adam D Ruppe wrote:

>

On Saturday, 24 July 2021 at 01:29:26 UTC, someone wrote:

>

Suppose I have a module with the following:

static if(is(classTickerCustomNYSE))
// it was a valid type
else
// it was not a valid type

can use that to test. you can also mix in the name

static if(is(mixin("class name here"))) {}

There's similar tricks for testing for imports and such too but i recommend here you import the module first then can test it.

is() ... faaan-tas-tic :)

I completely forgot about the is operator and went looking all over the place for something like that.

Man ... leaving templates aside for a moment, conditional compilation alongside mixin is pretty powerful in D ! I can't believe how flexible code I am writing right now; and I am only a beginner ...

Thanks for the tip Adam !