Is it possible for bridging object return some value in functions?

[bounin]

I tried to use your framework. Everything work perfectly except all functions returning something to javascript always show result as undefined in java script. For object properties everything is OK.

For example if my object has func1 returning string and in javascript I do:
var a = bridgingobject.func1(); // I get result undefined even the func1 defined as returning String (or NSString *). But if use property is starts working:
var a = bridgingobject.prop1; // exactly doing the same I get correct result. It just defined as property in Swift or Objective-C code, for objective-c it is even using same getter.
Thanks

[bounin]

Cannot be that related to the fact I loading web page from local storage?

[xwv]

Please see #52.

[bounin]

But how is the getting the value of the property works? It is essentially just getter function internally. And you get no problem with asynchronous calling it and get result back in one step.

[shirakaba]

I believe this is simply because when Javascript accesses a property on the bridging object, it just visits the address in memory for it and takes the value that is available at that exact moment. As you say, in this case, it works effectively like a getter.

Edit: Got confused when writing the initial reply - have removed this paragraph.

I think that invoking a Swift bridging object's method via JS should be thought of as the dispatching of an event (eg. EventTarget.dispatchEvent()) or request (eg. xmlhttprequest) rather than the running of a synchronous function. Could @xwv please clarify whether bridging object methods are similar to these two examples; and do they in fact have a return value, but only return asynchronously?

I recall that @xwv mentioned somewhere that it would theoretically be possible to block the JS environment so that it would wait synchronously for the return of the function from the Swift environment's bridging object, but that it would be very bad practice and undesirable for performance (and I agree!).

[xwv]

From javascript perspective, invoking a native function (or a setter) is sending a message. Somewhat like the behavior of event or xmlhttprequest, but totally different. The messaging interface is only available in WKWebKit framework. Script continues running while native is processing messages. To pass result back to javascript, native has to evaluate a callback function (in global scope).

Each property of bridging object has a 'cache' in JavaScript side. The getter merely returns the value in cache. XWebView tries to sync the cache with native value whenever it get changed by script or native. The syncing process is also async, so sometimes may cause problem.

[bounin]

Thank you, now it is clear. Property getter is only used by native part. And looking through the code you update JS counterpart property via KVO when value changes.