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unit iterator_intf;
{$mode objfpc}{$H+}
interface
uses
Classes
,SysUtils
;
type
{ A custom exception class }
ENoIteratorImpl = class(Exception);
EUniDirectionalIterator = class(Exception);
{ Standard iterators }
ITBIterator = interface(IInterface)
['{9C2BC10D-54C8-4B59-88B5-A564921CF0E3}']
function HasNext: Boolean;
function Next: TObject;
function HasPrevious: Boolean;
function Previous: TObject;
end;
ITBStringIterator = interface(IInterface)
['{B2A449B4-5D0A-4F14-AC11-CA055EDA3ED7}']
function HasNext: Boolean;
function Next: string;
function HasPrevious: Boolean;
function Previous: string;
end;
ITBStringAndObjectIterator = interface(ITBStringIterator)
['{287373DC-A90D-400E-BAEE-C85474C317A8}']
function HasNextObject: Boolean;
function NextObject: TObject;
function HasPreviousObject: Boolean;
function PreviousObject: TObject;
end;
ITBInterfaceIterator = interface
['{9B599C5B-4BBB-43F6-AF8E-09FEE9AE0E20}']
function HasNext: Boolean;
function Next: IInterface;
function HasPrevious: Boolean;
function Previous: IInterface;
end;
{ TODO:
More interfaces could be added for collections like:
TTreeView, TStringGrid etc... }
{ Filtered iterators }
ITBFilteredStringIterator = interface(ITBStringIterator)
['{CF1B9E2D-DD05-4D15-95C6-686EAFA4ED82}']
function GetFilter: string;
procedure SetFilter(const AValue: string);
property Filter: string read GetFilter write SetFilter;
end;
{ TODO:
More filtered versions of the standard iterators could
be added here... }
{ Iterator Factory }
TTBIteratorFactory = class(TObject)
function Iterator(const ASource: TObject): ITBIterator;
function StringIterator(const ASource: TObject): ITBStringIterator;
function StringAndObjectIterator(const ASource: TObject): ITBStringAndObjectIterator;
function InterfaceIterator(const ASource: TObject): ITBInterfaceIterator;
function FilteredStringIterator(const ASource: TObject; const AFilter: string): ITBFilteredStringIterator;
end;
{ Global iterator factory singleton }
function gIteratorFactory: TTBIteratorFactory;
implementation
uses
iterator_impl;
var
uIteratorFactory: TTBIteratorFactory;
const
cNoIteratorImpl = 'No Iterator implementation found for <%s>';
{ The lazy mans singleton implementation, but it does the job just fine. }
function gIteratorFactory: TTBIteratorFactory;
begin
if not Assigned(uIteratorFactory) then
uIteratorFactory := TTBIteratorFactory.Create;
Result := uIteratorFactory;
end;
{ TTBIteratorFactory }
function TTBIteratorFactory.Iterator(const ASource: TObject): ITBIterator;
begin
if ASource is TList then
Result := TTBListIterator.CreateCustom(TList(ASource))
else if ASource is TCollection then
Result := TTBCollectionIterator.CreateCustom(TCollection(ASource))
//else if ASource is TTreeNodes then
//Result := TTBTreeNodesIterator.CreateCustom(TTreeNodes(ASource))
else
raise ENoIteratorImpl.CreateFmt(cNoIteratorImpl, [ASource.ClassName]);
end;
function TTBIteratorFactory.StringIterator(const ASource: TObject): ITBStringIterator;
begin
if ASource is TStrings then
Result := TTBStringsIterator.CreateCustom(TStrings(ASource))
else
raise ENoIteratorImpl.CreateFmt(cNoIteratorImpl, [ASource.ClassName]);
end;
function TTBIteratorFactory.StringAndObjectIterator(const ASource: TObject): ITBStringAndObjectIterator;
begin
if ASource is TStrings then
Result := TTBStringsIterator.CreateCustom(TStrings(ASource))
else
raise ENoIteratorImpl.CreateFmt(cNoIteratorImpl, [ASource.ClassName]);
end;
function TTBIteratorFactory.InterfaceIterator(const ASource: TObject): ITBInterfaceIterator;
begin
if ASource is TInterfaceList then
Result := TTBInterfaceListIterator.CreateCustom(TInterfaceList(ASource))
else
raise ENoIteratorImpl.CreateFmt(cNoIteratorImpl, [ASource.ClassName]);
end;
function TTBIteratorFactory.FilteredStringIterator(const ASource: TObject; const AFilter: string): ITBFilteredStringIterator;
begin
if ASource is TStrings then
begin
Result := TTBFilteredStringsIterator.CreateCustom(TStrings(ASource));
Result.Filter := AFilter;
end
else
raise ENoIteratorImpl.CreateFmt(cNoIteratorImpl, [ASource.ClassName]);
end;
initialization
uIteratorFactory := nil;
finalization
uIteratorFactory.Free;
end.
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