想象一下,我想在VBA(伪代码)中做这样的事情,并假设我有一个可枚举的属性IDList:
Dim MyObject object
set MyObject= CreateObject("MyObjectClass")
for each Item as integer in MyObject.IDList
Debug.Write(Cstr(Item) & ";")
Next
在德尔福,我的财产IDList
会是什么样子?简单地从IEnumerable<integer>
或IEnumerable
推导它似乎没有做到这一点。
基本代码
为了避免使用默认的IENum
和IEnum<T>
接口的麻烦,我在Delphi端创建了我自己的枚举接口集,用于对象pascal for .. in ..
循环。
ISGEnumeratorBase= interface(IInterface)
['{DA91A203-3B39-4287-9A6F-6E9E4B184BAD}']
function MoveNext: Boolean;
end;
ISGEnumeratorReset = interface (ISGEnumeratorBase)
['{FBD2EFBD-D391-4BE2-A3AB-9C9D09197F78}']
procedure Reset;
end;
ISGEnumeratorClone = interface (ISGEnumeratorBase)
['{E3A128FD-7495-464D-BD5E-3EBA3AEFE94F}']
function Clone:ISGEnumeratorBase;
end;
/// <summary>
/// <para>
/// Required for implementing for..in loops
/// </para>
/// An alternative generic interface for the IEnumerator<T> defined
/// in the system unit. Allows for easier implementation of enumerators for
/// interfaced classes etc.
/// </summary>
ISGEnumerator<T> = interface(ISGEnumeratorBase)
function GetCurrent:T;
property Current: T read GetCurrent;
end;
/// <summary>
/// <para>
/// Required for implementing for..in loops
/// </para>
/// <para>
/// An alternative generic interface for the IEnumerator<T>
/// defined in the system unit. Allows for easier implementation of
/// enumerators for interfaced classes etc. <br />
/// </para>
/// </summary>
ISGEnumerable<T>=interface(IInterface)
function GetEnumerator:ISGEnumerator<T>;
end;
因此,我在我的应用程序中使用的枚举器使用这些接口来“发布”自己。我想要的是有一个适配器类,允许在IEnumVariant
和ISGEnumerator<T>
接口上创建ISGEnumerable<T>
接口
摘要
我创建了一个通用接口适配器,允许或多或少地轻松实现IEnumVariant
接口。我还发现IEnumVariant
接口是在Delphi提供的ActiveX
单元中定义的,它使用stdole32.tpl
作为类型库。
OLE枚举器基类
以下是枚举器基础和通用枚举器基类:
type
TSGOLEVariantEnumeratorAdapterBase=class (TAutoIntfObject,IEnumVariant)
private class var
vOLETypeLib:ITypeLib;
private
class function GetOLETypeLib: ITypeLib; static;
class Destructor ClassDestroy;
// for IOLEEnumVariant
function Next(celt: LongWord; var rgvar: OleVariant; out pceltFetched: Longword): HResult; stdcall;
function Skip(celt: LongWord): HResult; stdcall;
function Reset: HResult; stdcall;
function Clone(out Enum: IEnumVariant): HResult; stdcall;
protected
class property OLETypeLib:ITypeLib read GetOLETypeLib;
function DoNext(aFetchRequestCount: LongWord; var rgvar: OleVariant; out aActuallyFetchedCount: Longword): boolean; virtual; abstract;
function DoSkip(aSkipCOunt: LongWord): boolean; virtual; abstract;
function DoReset: boolean; virtual;
function DoClone(out Enum: IEnumVariant): boolean; virtual;
public
constructor Create;
end;
TSGGenericOLEVariantEnumeratorAdapter<TEnumeratedType>=class (TSGOLEVariantEnumeratorAdapterBase,ISGEnumerator<TEnumeratedType>)
private
FSourceEnumerator:ISGEnumerator<TEnumeratedType>;
protected
function MapCurrentToVariant(aCurrent:TEnumeratedType):olevariant; virtual;
function DoReset: boolean; override;
function DoClone(out Enum: IEnumVariant): boolean; override;
function DoNext(aFetchRequestCount: LongWord; var rgvar: OleVariant; out aActuallyFetchedCount: Longword): boolean; override;
function DoSkip(aSkipCOunt: LongWord): boolean; override;
property SourceEnumerator:ISGEnumerator<TEnumeratedType> read FSourceEnumerator implements ISGEnumerator<TEnumeratedType>;
public
constructor Create(const aSourceEnumerator:ISGEnumerator<TEnumeratedType>);
end;
我在实例化TAutoIntfObject基类和正确的类型库方面苦苦挣扎,但我终于成功地完成了下面的工作。我使用类var作为类型库,以避免一遍又一遍地加载它。
constructor TSGOLEVariantEnumeratorAdapterBase.Create;
begin
inherited Create(OLETypeLib,IEnumVariant);
end;
class destructor TSGOLEVariantEnumeratorAdapterBase.ClassDestroy;
begin
vOLETypeLib:=nil;
end;
class function TSGOLEVariantEnumeratorAdapterBase.GetOLETypeLib: ITypeLib;
begin
// HH we cannot lose Win.ComServ in a package
// thats why I cloned the call or LoadTypeLibrary here
if not Assigned(vOLETypeLib) then
OleCheck(LoadTypeLibEx('stdole32.tlb', REGKIND_NONE, vOLETypeLib));
Result:=vOLETypeLib;
end;
之后我实现了接口的方法,也允许为dispintf
正确处理异常。循环实现的实际“肉”放在从接口方法调用的虚拟方法中。接口方法如下所示:
function TSGOLEVariantEnumeratorAdapterBase.Next(celt: LongWord; var rgvar: OleVariant;
out pceltFetched: Longword): HResult;
VAR lActuallyFetched:longword;
begin
lActuallyFetched:=0;
try
if DoNext(celt,rgvar,lActuallyFetched) then
Result:=S_OK
else Result:=S_FALSE;
if Assigned(@pceltFetched) then
pceltFetched:=lActuallyFetched;
except
Result:=SafeCallException(ExceptObject,ExceptAddr);
end;
end;
function TSGOLEVariantEnumeratorAdapterBase.Skip(celt: LongWord): HResult;
begin
try
if DoSkip(celt) then
Result:=S_OK
else Result:=S_FALSE;
except
Result:=SafeCallException(ExceptObject,ExceptAddr);
end;
end;
function TSGOLEVariantEnumeratorAdapterBase.Reset: HResult;
begin
try
if DoReset then
Result:=S_OK
else Result:=S_FALSE;
except
Result:=SafeCallException(ExceptObject,ExceptAddr);
end;
end;
function TSGGenericOLEVariantEnumeratorAdapter<TEnumeratedType>.DoClone(out Enum: IEnumVariant): boolean;
VAR lCloneIntf:ISGEnumeratorClone;
lCLonedEnumerator:ISGEnumerator<TEnumeratedType>;
begin
if Supports(FSourceEnumerator,ISGEnumeratorClone,lCloneIntf) then
begin
lCLonedEnumerator:=ISGEnumerator<TEnumeratedType>(lCloneIntf.Clone);
Enum:=TSGGenericOLEVariantEnumeratorAdapter<TEnumeratedType>(self.ClassType).Create(lCLonedEnumerator);
Result:=True;
end
else Result :=inherited;
end;
function TSGOLEVariantEnumeratorAdapterBase.Clone(out Enum: IEnumVariant): HResult;
begin
try
if DoClone(Enum) then
Result:=S_OK
else Result:=S_FALSE;
except
Result:=SafeCallException(ExceptObject,ExceptAddr);
end;
end;
克隆和重置我已经为Clone
和Reset
方法添加了虚拟方法,但实际上在我的示例中没有从Excel VBA中调用这些方法,
通用IEnumVariant适配器类接下来是创建通用适配器,它覆盖Doxxx方法并添加MapCurrentToVariant
例程以从源枚举器获取“当前”值到输出变量。此例程是虚拟的,因此可以覆盖它以进行特殊或更有效的转换。
因此泛型类看起来像这样:
TSGGenericOLEVariantEnumeratorAdapter<TEnumeratedType>=class (TSGOLEVariantEnumeratorAdapterBase,ISGEnumerator<TEnumeratedType>)
private
FSourceEnumerator:ISGEnumerator<TEnumeratedType>;
protected
function MapCurrentToVariant(aCurrent:TEnumeratedType):olevariant; virtual;
function DoReset: boolean; override;
function DoClone(out Enum: IEnumVariant): boolean; override;
function DoNext(aFetchRequestCount: LongWord; var rgvar: OleVariant; out aActuallyFetchedCount: Longword): boolean; override;
function DoSkip(aSkipCOunt: LongWord): boolean; override;
property SourceEnumerator:ISGEnumerator<TEnumeratedType> read FSourceEnumerator implements ISGEnumerator<TEnumeratedType>;
public
constructor Create(const aSourceEnumerator:ISGEnumerator<TEnumeratedType>);
end;
实现重写的例程非常简单。
constructor TSGGenericOLEVariantEnumeratorAdapter<TEnumeratedType>.Create(
const aSourceEnumerator: ISGEnumerator<TEnumeratedType>);
begin
FSourceEnumerator:=aSourceEnumerator;
inherited Create;
end;
function TSGGenericOLEVariantEnumeratorAdapter<TEnumeratedType>.MapCurrentToVariant(aCurrent: TEnumeratedType): olevariant;
begin
Result:=TValue.From<TEnumeratedType>(aCurrent).AsVariant;
end;
function TSGGenericOLEVariantEnumeratorAdapter<TEnumeratedType>.DoNext(aFetchRequestCount: LongWord;
var rgvar: OleVariant; out aActuallyFetchedCount: Longword): boolean;
type
TVariantList=array[0..0] of Olevariant;
begin
aActuallyFetchedCount:=0;
while (aFetchRequestCount>0) and SourceEnumerator.MoveNext do
begin
dec(aFetchRequestCount);
TVariantList(rgvar)[aActuallyFetchedCount]:=MapCurrentToVariant(SourceEnumerator.Current);
inc(aActuallyFetchedCount);
end;
Result:=(aFetchRequestCount=0);
end;
function TSGGenericOLEVariantEnumeratorAdapter<TEnumeratedType>.DoSkip(aSkipCOunt: LongWord): boolean;
begin
while (aSkipCount>0) and SourceEnumerator.MoveNext do
dec(aSkipCount);
Result:=(aSkipCOunt=0);
end;
我稍后添加了Clone
和Reset
选项,因为它们实际上并未被我的应用程序使用,因此可能将来使用。实现看起来像这样:
function TSGGenericOLEVariantEnumeratorAdapter<TEnumeratedType>.DoClone(out Enum: IEnumVariant): boolean;
VAR lCloneIntf:ISGEnumeratorClone;
lCLonedEnumerator:ISGEnumerator<TEnumeratedType>;
begin
if Supports(FSourceEnumerator,ISGEnumeratorClone,lCloneIntf) then
begin
lCLonedEnumerator:=ISGEnumerator<TEnumeratedType>(lCloneIntf.Clone);
Enum:=TSGGenericOLEVariantEnumeratorAdapter<TEnumeratedType>(self.ClassType).Create(lCLonedEnumerator);
Result:=True;
end
else Result :=inherited;
end;
function TSGGenericOLEVariantEnumeratorAdapter<TEnumeratedType>.DoReset: boolean;
VAR lResetIntf:ISGEnumeratorReset;
begin
if Supports(FSourceEnumerator,ISGEnumeratorReset,lResetIntf) then
begin
lResetIntf.Reset;
Result:=True;
end
else Result := inherited;
end;
最后,我决定创建一个可枚举的适配器类,在某些情况下可能会派上用场:
TSGGenericOLEVariantEnumerableAdapter<TEnumeratedType>=class (TAutoIntfObject,ISGEnumerable<TEnumeratedType>)
private
FSourceEnumerable:ISGEnumerable<TEnumeratedType>;
protected
function Get__NewEnum: IUnknown; safecall; inline;
property SourceEnumerable:ISGEnumerable<TEnumeratedType> read FSourceEnumerable implements ISGEnumerable<TEnumeratedType>;
public
constructor Create(const aTypeLib:ITypeLib;const aDispIntf:TGUID;const aSourceEnumerable:ISGEnumerable<TEnumeratedType>);
end;
该类的实施:
constructor TSGGenericOLEVariantEnumerableAdapter<TEnumeratedType>.Create(const aTypeLib:ITypeLib;const aDispIntf:TGUID;const aSourceEnumerable:ISGEnumerable<TEnumeratedType>);
begin
FSourceEnumerable:=aSourceEnumerable;
inherited Create(aTypeLib,aDispIntf);
end;
function TSGGenericOLEVariantEnumerableAdapter<TEnumeratedType>.Get__NewEnum: IUnknown;
begin
Result:=TSGGenericOLEVariantEnumeratorAdapter<TEnumeratedType>.Create(SourceEnumerable.GetEnumerator);
end;
在我计划使用我的代码的地方,一切看起来都很干净,而且只需要很少实现。下面是一个枚举器的示例,用于从我的实际应用程序模型中获取一堆对象ID:
TAMDBObjIDEnumeratorAdapter=class (TSGGenericOLEVariantEnumeratorAdapter<integer>);
TAMDBObjIDEnumerableAdapter=class (TSGGenericOLEVariantEnumerableAdapter<integer>,IAMObjectIDs,ISGEnumerable<integer>)
public
constructor Create(const aSourceEnumerable:ISGEnumerable<integer>);
end;
....
constructor TAMDBObjIDEnumerableAdapter.Create(const aSourceEnumerable: ISGEnumerable<integer>);
begin
inherited Create(comserver.TypeLib,IAMObjectIDs,aSOurceEnumerable);
end;
代码实际上已经使用Excel和Delphi进行了测试,但是为Delphi枚举器提供我的内部解决方案的所有代码超出了这个问题的主题,那就是为什么我没有为此创建一个演示项目。谁知道,如果我找到时间和足够的赞成/请求,我可能会在这方面投入更多精力。我希望我在Delphi中寻找“工作和清洁”解决方案的过程将有助于其他人。