How to pass a reference to a JS function as an argument to an ExternalInterface call?
- by Ryan Wilson
Summary
I want to be able to call a JavaScript function from a Flex app using ExternalInterface and pass a reference to a different JavaScript function as an argument.
Base Example
Given the following JavaScript:
function foo(callback)
{
// ... do some stuff
callback();
}
function bar()
{
// do some stuff that should happen after a call to foo
}
I want to call foo from my flex app using ExternalInterface and pass a reference to bar as the callback.
Why
Really,foo is not my function (but, rather, FB.Connect.showBookmarkDialog), which due to restrictions on Facebook iframe apps can only be called on a button click. My button, for design reasons, is in the Flex app. Fortunately, it's possible to call ExternalInterface.call("FB.Connect.showBookmarkDialog", callback) to display the bookmark dialog. But, FB.Connect.showBookmarkDialog requires a JS callback so, should I want to receive a callback (which I do), I need to pass a reference to a JS function as the single argument.
Real Example
MXML:
<mx:Button click="showBookmarkDialog();" />
ActionScript:
function showBookmarkDialog() : void
{
ExternalInterface.registerCallback(
"onBookmarkDialogClosed",
onBookmarkDialogClosed
);
ExternalInterface.call(
"FB.Connect.showBookmarkDialog",
/* ref to JS function onBookmarkDialogClosed ? */
);
}
function onBookmarkDialogClosed(success:Boolean) : void
{
// sweet, we made it back
}
JavaScript:
function onBookmarkDialogClosed()
{
var success;
// determine value of success
getSWF().onBookmarkDialogClosed(success);
}
Failed Experiments
I have tried...
ExternalInterface.call(
"FB.Connect.showBookmarkDialog",
"onBookmarkDialogClosed"
);
ExternalInterface.call(
"FB.Connect.showBookmarkDialog",
onBookmarkDialogClosed
);
ExternalInterface.call(
"FB.Connect.showBookmarkDialog",
function() : void
{
ExternalInterface.call("onBookmarkDialogClosed");
}
);
ExternalInterface.call(
"FB.Connect.showBookmarkDialog",
function()
{
this["onBookmarkDialogClosed"]();
}
);
Of note:
Passing a string as the argument to an ExternalInterface call results in FB's JS basically trying to do `"onBookmarkDialogClosed"()` which, needless to say, will not work.
Passing a function as the argument results in a function object on the other side (confirmable with `typeof`), but it seems to be an empty function; namely, `function Function() {}`
