own namespace for nested enums in Delphi

Question

Is there a way to put nested enumerations in Delphi into an own naming space?

This code produces an E2004: Identifier redeclared, as both enumerations contain "unknown".

TMyType1 = class
public type
  TMyType1Enum = (unknown, val1, val2);
public
  constructor Create();
  ...
end;

TMyType2 = class
public type
  TMyType2Enum = (unknown, other1, other2, other3); // causes E2004
public
  constructor Create();
  ...
end;

In C++ the identifiers of the enum elements were both in differnet scopes (TMyType1::unknown and TMyType2::unknown).

Is there a possibility to achieve something like this in Delphi except pre- or suffixing the identifiers (MyType1EnumUnknown, MyType1EnumVal1, ..., MyType2Enumunknown,...)?

The answer below is perfect but from a coding standards point of view, prefixes are normally used in Delphi for enums. Take a look at `TFontStyle`, as an example. It's definition looks like this: `TFontStyle = (fsBold, fsItalic, fsUnderline, fsStrikeOut)` — Graymatter, Jul 29 '16 at 18:40

score 13 · Accepted Answer · edited Jul 29 '16 at 11:53

13

Try $SCOPEDENUMS. From http://docwiki.embarcadero.com/RADStudio/en/Scoped_Enums_(Delphi):

type
  TFoo = (A, B, Foo);
  {$SCOPEDENUMS ON}
  TBar = (A, B, Bar);
  {$SCOPEDENUMS OFF}

begin
  WriteLn(Integer(Foo)); 
  WriteLn(Integer(A)); // TFoo.A
  WriteLn(Integer(TBar.B));
  WriteLn(Integer(TBar.Bar));
  WriteLn(Integer(Bar)); // Error
end;

edited Jul 29 '16 at 11:53

David Heffernan

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answered Jul 29 '16 at 10:07

Uli Gerhardt

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FWIW, the docwiki seems to be offline, right now. But the same documentation can be found in the installed help files that come with Delphi/RAD Studio. We just can't link to it, from here. – Rudy Velthuis Nov 19 '17 at 10:27

own namespace for nested enums in Delphi

1 Answers1