delphi - 如何使用 Delphi 6 迭代初始化枚举类型并避免 "out of bounds"错误？

Question

我使用的是 Delphi 6 Professional。我正在与一个 DLL 库交互，该库声明了一个枚举类型，如下所示:

TExtDllEnum = (ENUM1 = $0, ENUM2 = $1, ENUM3 = $2, ENUM4 = $4, ENUM5 = $8, ENUM6 = $10);

正如您所看到的，初始化值不是连续的。如果我尝试使用 for 循环迭代该类型，如下所示:

var
    e: TExtDllEnum;
begin
    for e := Low(TExtToDllEnum) to High(TExtToDllEnum) do
    ... // More code
end;

Delphi 仍然在每次循环调用时将 e 加 1，从而为 e 创建不是枚举类型成员的数值(例如“3”)，并导致“越界”错误。如何在 for 循环中迭代枚举类型，从而仅生成枚举类型的有效值？

谢谢。

Answer 1

通过定义一组常量...

type
  TExtDllEnum = (ENUM1 = $0, ENUM2 = $1, ENUM3 = $2, ENUM4 = $4, ENUM5 = $8, ENUM6 = $10);

const
  CExtDllEnumSet = [ENUM1, ENUM2, ENUM3, ENUM4, ENUM5, ENUM6];


var
  e: TExtDllEnum;
begin
  e := Low(TExtDllEnum);
  while e <= High(TExtDllEnum) do
  begin
    if e in CExtDllEnumSet then 
      WriteLn(Ord(e));

    Inc(e);
  end;

  ReadLn;
end.

<小时/>

并作为迭代器实现 - 只是为了好玩......

type
  TExtDllEnum = (ENUM1 = $0, ENUM2 = $1, ENUM3 = $2, ENUM4 = $4, ENUM5 = $8, ENUM6 = $10);
const
  CExtDllEnumSet = [ENUM1, ENUM2, ENUM3, ENUM4, ENUM5, ENUM6];

type
  TMyIterator = class
  private
    FValue: TExtDllEnum;
  public
    constructor Create;
    function Next: TExtDllEnum;
    function HasNext: Boolean;
  end;

  constructor TMyIterator.Create;
  begin
    FValue := Low(TExtDllEnum);
  end;

  function TMyIterator.HasNext: Boolean;
  begin
    Result := FValue <= High(TExtDllEnum);
  end;

  function TMyIterator.Next: TExtDllEnum;
  begin
    Result := FValue;

    repeat
      Inc(FValue);
    until (FValue in CExtDllEnumSet) or (FValue > High(TExtDllEnum))
  end;

var
  MyIterator: TMyIterator;
begin
  MyIterator := TMyIterator.Create;

  while MyIterator.HasNext do
    WriteLn(Ord(MyIterator.Next));

  MyIterator.Free;

  ReadLn;
end.