javascript calling DataSnap REST makes browser unresponsive

Question

I use Delphi XE7. When my Javascript calls my server function that need around 800ms to read sensor and return data, The browser is unresponsive from the moment I click the button to invoke the Javascript until it finally response returns. I'm using the default Javascript generated by the proxy var serverMethods().getChannel(i); to call into my server function.

Javascript call look like this:

var s = serverMethods().getChannel(i);
      serial[i].$sensorlValue.text(s.result.fields.sensorString);
      serial[i].$sensorlRealValue.text(s.result.fields.sensor);
      serial[i].$sensorStatus.text(s.result.fields.sensorStatus+' '+s.result.fields.name);
      serial[i].$sensorError.text(s.result.fields.sensorError);
      serial[i].$AVString.text(s.result.fields.AVString);
      serial[i].$AVError.text(s.result.fields.AVError);

So by default example there are no Javascript callbacks or promise, so embaracaderom manage somehow to block Javascript from executing until response is back and variable a receive values?

I think about try using jQuery Ajax call on URL, but is there any other solution?

Because serverMethods are generated from proxy but for $ajax I need to manually set each of them. Or maybe I do something wrong here and serverMethods can be used without blocking ?

Thanks.

Answer 1

I found the solution to this problem after researching execution path in ServerFunctionExecutor.js that is called on serverMethods().SOMEAPIFUNCTION() 1. Help and documentation are 0, and google + XE7 questions are 0. So if someone from embaracadero read this PLS MAKE DECENT DOCUMENTATION.

ServerFunctionExecutor.js had on line 263

   //async is only true if there is a callback that can be notified on completion
var useCallback = (callback != null);
request.open(requestType, url, useCallback);

if (useCallback)
{
  request.onreadystatechange = function() {
    if (request.readyState == 4)
    {
      //the callback will be notified the execution finished even if there is no expected result
      JSONResult = hasResult ? parseHTTPResponse(request) : null;
      callback(JSONResult, request.status, owner);
    }
  };
}

So it is posible and NOT DOCUMENTED to use callback for unblocking GUI. Use it as:

serverMethods().SOMEAPIFUNCTION(par1,par2,.... callback)

If you have Server method defined in delphi code with for example 3 parameters in js 4th parameter is callback:

For this example code now look like this:

 serverMethods().getChannel(i,function(a,b,c){
            serial.$sensorlValue.text(a.result[0].fields.sensorString);
            serial.$sensorlRealValue.text(a.result[0].fields.sensor);
            serial.$sensorStatus.text(a.result[0].fields.sensorStatus+' '+s.result.fields.name);
            serial[i].$sensorError.text(a.result[0].fields.sensorError);
            serial[i].$AVString.text(a.result[0].fields.AVString);
            serial[i].$AVError.text(a.result[0].fields.AVError);
          });

a is JSON reponse
b is Request status as number 200 or somethin else
c is owner usuali undefined