我正在使用Delphi 6 Professional.我正在与DLL libraty接口,它声明了一个enumberated类型,如下所示：
TExtDllEnum = (ENUM1 = $0,ENUM2 = $1,ENUM3 = $2,ENUM4 = $4,ENUM5 = $8,ENUM6 = $10);
如您所见,初始值不是连续的.如果我尝试使用for循环迭代类型,如下所示：
var
e: TExtDllEnum;
begin
for e := Low(TExtToDllEnum) to High(TExtToDllEnum) do
... // More code
end;
Delphi仍然将每个循环调用增加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,该循环只生成枚举类型的有效值？
谢谢.
解决方法
通过定义一组常量……
type
TExtDllEnum = (ENUM1 = $0,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.
并实现为迭代器 – 只是为了好玩…
type
TExtDllEnum = (ENUM1 = $0,ENUM6 = $10);
const
CExtDllEnumSet = [ENUM1,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.