Question

I’m trying to create a function that shows a modal dialog which when called blocks until the dialog is closed, this will allow for a result to be returned to the caller

The following function is an attempt which has two problems.

1. It returns the result while the dialog is still open.
2. The selector test does not find the dialog, inspecting with firebug reveals that the id element is lost once the dialog is created.

.

function getCountrySelection() {
    var ctryCode;
    var dlg = $("#JS-field-dlg-ctry-select");

    if (dlg.size() === 0) {
        dlg = $("<div id='JS-field-dlg-ctry-select' title='Select Country' class='dialog-fields'></div>");
        dlg.append("Customer found in both Australia and New Zealand");
        dlg.dialog({
            autoOpen: false,
            width: 400,
            height: 160,
            modal: true,

            buttons: {
                "Australia": function() {
                    ctryCode = "au";
                    $(this).dialog("close");
                },
                "New Zealand": function() {
                    ctryCode = "nz";
                    $(this).dialog("close");
                },
                "Cancel": function() {
                    $(this).dialog("close");
                }
            }
        });
    }

    dlg.dialog('open');

    return ctryCode;
}

EDIT: I thought I’d show how I’m calling this:

buttons: {
    "Find": function() {
        var custAu = JS.sales.getCustomer("au", inpCust.val());
        var custNz = JS.sales.getCustomer("nz", inpCust.val());

        var cust;
        if (custAu === undefined && custNz === undefined) {
            alert('No customer could be found with that number.');
            return;
        } else if (custAu !== undefined && custNz !== undefined) {
            var ctry;
            getCountrySelection(function(result) {
                ct = result;
            });
            if (ctry === "au") {
                cust = custAu;
            } else if (ctry === "nz") {
                cust = custNz;
            } else {
                return;
            }
        } else if (custNz === undefined) {
            cust = custAu;
        } else {
            cust = custNz;
        }

        if (cust) {
            $(this).dialog("close");
            // Do something with cust.
        } else {
            alert('Customer could not be found.');
        }
    },
    "Cancel": function() {
        $(this).dialog("close");
    }
}

Answer 1

There is no way to block execution until the dialog closes; JavaScript does not allow to “suspend” execution. Your best bet is to change the contract of your function; instead of returning the value straight away, it should accept a callback function that it will call with the result as soon as the dialog is dismissed. Then the code calling this will provide a suitable callback in which it can continue its execution.

Something like this:

function getCountrySelection(callback) {
(...)
            buttons: {
                "Australia": function() {
                    $(this).dialog("close");
                    callback("au");
                },
                "New Zealand": function() {
                    $(this).dialog("close");
                    callback("nz");
                },
                "Cancel": function() {
                    $(this).dialog("close");
                    callback();
                }
            }
        });
    }
    dlg.dialog('open');
}

Then use:

getCountrySelection(function(result) {
    if (result) {
        ...handle result...
    } else {
        ...the user cancelled the dialog...
    }
});

This is basically the same thing as with AJAX calls; you can’t “suspend” your AJAX call to wait until the AJAX actually completes and returns the result, hence “asynchronous”.

EDIT: In your specific example, you could use it like this:

buttons: {
    "Find": function() {
        var custAu = JS.sales.getCustomer("au", inpCust.val());
        var custNz = JS.sales.getCustomer("nz", inpCust.val());

        if (custAu === undefined && custNz === undefined) {
            alert('No customer could be found with that number.');
            return;
        } else if (custAu !== undefined && custNz !== undefined) {
            getCountrySelection(function(ctry) {
                var cust;
                if (ctry === "au") {
                    cust = custAu;
                } else if (ctry === "nz") {
                    cust = custNz;
                } 
                handleCustomer(cust);
            });
        } else if (custNz === undefined) {
            handleCustomer(custAu);
        } else {
            handleCustomer(custNz);
        }

        function handleCustomer(cust) {
            if (cust) {
                $(this).dialog("close");
                // Do something with cust.
            } else {
                alert('Customer could not be found.');
            }            
        }
    },
    "Cancel": function() {
        $(this).dialog("close");
    }
}