How do i return an object from a function in Delphi without causing Access Violation?

Question

I have a delphi function that returns a TStringList, but when I return a value and try to use it I get a Access Violation Error i.e

myStringList := FuncStringLis         


        

Answer 1

Either as Out variable.

function GetList(Parameter1: string; out ResultList: TStringList): boolean;
begin
  // either
  if not Assigned(ResultList) then
    raise Exception.Create('Out variable is not declared.');
  // or
  Result := False;
  if not Assigned(ResultList) then
    Exit;
  ResultList.Clear;
  ResultList.Add('Line1');
  ResultList.Add('Line2');
  //...
  Result := True;
end;

Or as string.

function GetList(Parameter1: string): string;
var
  slList: TStringList;
begin
  slList := TStringList.Create;
  try
    slList.Clear;
    slList.Add('Line1');
    slList.Add('Line2');
    //...
    Result := slList.Text;
  finally
    slList.Free;
  end;
end;

.

procedure Main;
var
  slList: TStringList;
begin
  slList := TStringList.Create;
  try
    // either
    GetList(Parameter1, slList);
    // or
    slList.Text := GetList(Parameter1);
    // process slList...
  finally
    slList.Free;
  end;
end;