Enum values in their own namespaces/scopes: Scoped Enums (Delphi)

A while ago, I needed several enum types in the same unit with overlapping enumeration values.

Putting each in an encompassing type wasn’t possible and I didn’t want to put each in their own unit.

Luckily, Delphi 2009 introduced the “scoped enum” feature effectively promoting the enumeration type into a scope or namespace.

It is only available at the source code level, as – at least up until Delphi 10.1 Berlin – it is not part of the compiler settings in the project options (see screenshot below).

Since the below was hard to find combined with the word “namespace” I’ve quoted it in full:

Type	Switch
Syntax	{$SCOPEDEUNMS ON}, or {$SCOPEDENUMS OFF}
Default	{$SCOPEDENUMS OFF}
Scope	Local

Remarks

The $SCOPEDENUMS directive enables or disables the use of scoped enumerations in Delphi code. More specifically, $SCOPEDENUMS affects only definitions of new enumerations, and only controls the addition of the enumeration’s value symbols to the global scope.

In the {$SCOPEDENUMS ON} state, enumerations are scoped, and enum values are not added to the global scope. To specify a member of a scoped enum, you must include the type of the enum. For example:

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;

Note that this is also valid:

 Writeln(Integer(TFoo.A));

Even though TFoo was not declared with $SCOPEDENUMS ON, the A value can still be explicitly resolved using the enumeration name.

–jeroen

Source: [WayBack] Scoped Enums (Delphi)

via [WayBack] own namespace for nested enums in Delphi – Stack Overflow

The Project Options do not have a “scoped enum” entry under the compiler settings: