我有这个原子乐观的初始化类：
type
Atomic<T: IInterface> = class
type TFactory = reference to function: T;
class function Initialize(var storage: T; factory: TFactory): T;
end;
class function Atomic<T>.Initialize(var storage: T; factory: TFactory): T;
var
tmpIntf: T;
begin
if not assigned(storage) then begin
tmpIntf := factory();
if InterlockedCompareExchangePointer(PPointer(@storage)^,PPointer(@tmpIntf)^,nil) = nil then
PPointer(@tmpIntf)^ := nil;
end;
Result := storage;
end;
现在我想为对象实现相同的模式.
type
Atomic<T: class> = class
type TFactory = reference to function: T;
class function Initialize(var storage: T; factory: TFactory): T;
end;
class function Atomic<T>.Initialize(var storage: T; factory: TFactory): T;
var
tmpIntf: T;
begin
if not assigned(storage) then begin
tmpIntf := factory();
if InterlockedCompareExchangePointer(PPointer(@storage)^,nil) = nil then
tmpIntf.Free;
end;
Result := storage;
end;
我可以在两个单独的类中完成这两个,但我真的想把两个初始化器放在同一个伞下.我想,我最好还是喜欢这个
var o: TObject; i: IInterface; Atomic<TObject>.Initialize(o,CreateObject); Atomic<IInterface>.Initialize(i,CreateInterface);
我找不到任何好的解决方案.我得到的唯一想法是将类声明为Atomic< T> (没有约束)然后以某种方式(还不知道如何)在运行时检查T的RTTI并相应地继续.
我不太喜欢这个想法,我正在寻找一个更好的方法.
解决方法
您似乎无法指定“类或接口”类型的约束.因此,最简单的解决方案似乎是删除约束(您可以在运行时使用RTTI强制执行它).
uses
...,TypInfo;
class function Atomic<T>.Initialize(var storage: T; factory: TFactory): T;
var
tmpT: T;
begin
if not assigned(PPointer(@storage)^) then begin
tmpT := factory();
if InterlockedCompareExchangePointer(PPointer(@storage)^,PPointer(@tmpT)^,nil) = nil then begin
case PTypeInfo(TypeInfo(T))^.Kind of
tkInterface:
PPointer(@tmpT)^ := nil;
tkClass:
TObject(tmpT).Free;
else
raise Exception.Create('Atomic<T>.Initialize: Unsupported type');
end;
end;
end;
Result := storage;
end;