Question

Here is my code:

var
  xhttp: OleVariant;

xhttp := CreateOleObject('MSXML2.XMLHTTP');
xhttp.Open('GET', URL, True);
xhttp.send();

while xhttp.readyState <> 4 do
begin
  Application.HandleMessage;        
end;

// status property is available only when readyState is complete
if (xhttp.Status = 200) then... 
// do something

In this situation I do not want to use the event onreadystatechange.

The Question:
Is it safe to poll on the readyState for a value of 4, after I call Send, or is there a risk to be stuck in an endless loop?

---

Some facts:

The ServerXMLHTTPRequest can use a waitForResponse inside the loop, but I want to use XMLHTTPRequest component.
It is stated there that:

The waitForResponse method is more efficient than polling the
readyState property, which is the only way to wait for an asynchronous
send using the XMLHTTP component.

Answer 1

If you are worried about an endless loop, then simply implement a timeout for your loop, eg:

var 
  xhttp: OleVariant; 
  Ticks: DWORD;

  function TimeoutElapsed: Boolean;
  var
    Cur, Elapsed: DWORD;
  begin
    Cur := GetTickCount();
    if Cur >= Ticks then
      Elapsed := Cur - Ticks
    else
      Elapsed := (MAXDWORD - Ticks) + Cur;
    Result := (Elapsed >= 15000);
  end;

begin
  xhttp := CreateOleObject('MSXML2.XMLHTTP'); 
  xhttp.Open('GET', URL, True); 
  xhttp.send(); 

  Ticks := GetTickCount();
  while (xhttp.readyState <> 4) and (not TimeoutElapsed()) do
  begin
    if MsgWaitForMultipleObjects(0, nil, False, 1000, QS_ALLINPUT) = WAIT_OBJECT_0 then
      Application.ProcessMessages();         
    Ticks := GetTickCount();
  end; 

  // status property is available only when readyState is complete 
  if xhttp.readyState = 4 then
  begin
    if (xhttp.Status = 200) then...  
  end;
end;