Optional Anonymous Method - delphi

Question

I would like to expose a function that can take an optional anonymous method :
type
TParamsProc = reference to procedure(Params: TSQLParams);
TFieldsProc = reference to procedure(Fields: TSQLResult);
TDbController = class
...
public
procedure Select(const SQL: sting; ParamsProc: TParamsProc; FieldsProc: TFieldsProc);
end;
implementation
procedure TDbController.Select(const SQL: sting; ParamsProc: TParamsProc; FieldsProc: TFieldsProc);
var
Q: TUIBQuery;
begin
Q := TUIBQuery.Create(nil);
try
Q.Database := FDatabase;
Q.Transaction := FTransaction;
Q.SQL.Text := SQL;
ParamsProc(Q.Params);
Q.Open;
while not Q.Eof do
begin
FieldsProc(Q.Result);
Q.Next;
end;
finally
Q.Free;
end;
end;
As sometimes I have no params to pass to a SQL Query, I would like to make the ParamsProc optional.
this code don't work :
if ParamsProc <> nil then ParamsProc(Q.Params);
nor this one :
if #ParamsProc <> nil then ParamsProc(Q.Params);
The first one don't compile, the second one compile but don't work because ParamsProc has always a non nil value.
Example of call :
FController.Select(
'select A, B, C from SOME_TABLE',
nil,
procedure(Fields: TSQLResult)
begin
FA := Fields.AsInteger[0];
FB := Fields.AsString[1];
FC := Fields.AsCurrency[2];
end
);
Edit
Seems that Assigned(ParamsProc) do the trick.

Answer 1

Following Jeroen Pluimers advice, I make my "Edit" an "Answer" :
Assigned(ParamsProc) do the trick :
procedure TDbController.Select(const SQL: sting; ParamsProc: TParamsProc; FieldsProc: TFieldsProc);
var
Q: TUIBQuery;
begin
Q := TUIBQuery.Create(nil);
try
Q.Database := FDatabase;
Q.Transaction := FTransaction;
Q.SQL.Text := SQL;
if Assigned(ParamsProc) then
ParamsProc(Q.Params);
Q.Open;
while not Q.Eof do
begin
FieldsProc(Q.Result);
Q.Next;
end;
finally
Q.Free;
end;
end;
Hope this helps !