How to create an instance of object with RTTI in Delphi 2010?
- by Paul
As we all known, when we call a constructor of a class like this:
instance := TSomeClass.Create;
The Delphi compiler actually do the following things:
Call the static NewInstance method
to allocate memory and initialize
the memory layout.
Call the constructor method to
perform the initialization of the class
Call the AfterConstruction method
It's simple and easy to understand. but I'm not very sure how the compiler handle exceptions in the second and the third step.
It seems there are no explicit way to create an instance using a RTTI constructor method in D2010. so I wrote a simple function in the Spring Framework for Delphi to reproduce the process of the creation.
class function TActivator.CreateInstance(instanceType: TRttiInstanceType;
constructorMethod: TRttiMethod; const arguments: array of TValue): TObject;
var
classType: TClass;
begin
TArgument.CheckNotNull(instanceType, 'instanceType');
TArgument.CheckNotNull(constructorMethod, 'constructorMethod');
classType := instanceType.MetaclassType;
Result := classType.NewInstance;
try
constructorMethod.Invoke(Result, arguments);
except
on Exception do
begin
if Result is TInterfacedObject then
begin
Dec(TInterfacedObjectHack(Result).FRefCount);
end;
Result.Free;
raise;
end;
end;
try
Result.AfterConstruction;
except
on Exception do
begin
Result.Free;
raise;
end;
end;
end;
I feel it maybe not 100% right. so please show me the way. Thanks!
