AJAX interface

JSON request/reply flow

REQUEST:

{module: "M", action: "A", event: "E", data: D}

• event is optional, when omited, E = “M:A” is assumed
• data is optional
• D is any JSON value

REPLY:

{event: "E-atom", reply: R}

• atom is “ok” | “fail”, but can also be other word
• R is any JSON value

JavaScript side

Preamble:

<script src="js/json2.js" type="text/javascript"></script>
<script src="MochiKit/MochiKit.js" type="text/javascript"></script>
<script src="js/enge.js" type="text/javascript"></script>

<script type="text/javascript">
function pageLoadFunction(){

    // on-click handlers
    connect('testButton', 'onclick', doTest);

    // ajax reply event handlers
    connect(xapi, 'test:test-ok', cbTestOk);
    connect(xapi, 'test:test-fail', cbTestFail);  // optional handler
}

MochiKit.Signal.connect(window, "onload", pageLoadFunction);
</script>

Call:

function doTest(){
    var json = {
        "module": "test",
        "action": "test",
    }
    ajax(json, "/enge");
}

Event handler:

function cbTestOk(json){
    // json.reply is object
    $('testResult').innerHTML = json.reply.preamble + json.reply.sid;
    Highlight('testResult');
}

function cbTestFail(json){
    // json.reply is plain value
    $('testResult').innerHTML = "Error: " + json.reply;
    Highlight('testResult');
}

Erlang side

Erlang module must be prefixed with “ajax”, which is omited in JSON request.

Any function, exported from ajax_Something module can be accessed via JSON request (caller’s permissions are checked).

Function result is: {atom(), value(), headers()}

• atom(): ok | fail | something-other
• value(): erlang representation of JSON value
• headers(): list of headers to set via http (in future versions may contain other directives to web engine)

-module(ajax_test).
-compile(export_all).

-include("session.hrl").

test(Struct, Session, _Req) ->
    case Session of
        #session{sid = {auth, Sid}} ->
            % reply is object
            {{ok, {obj, [{"preamble", <<"Test ok the sid is">>},
                         {"sid", list_to_binary(Sid)}]}},
             []};
        _ ->
            % reply is binary
            {{fail, <<"No session">>}, []}
    end.