Nativescript: iOS: dispatch_async(dispatch_get_main_queue() ... possible?

Created on 1 Mar 2016 · 13Comments · Source: NativeScript/NativeScript

I have not been able to find an example of how to run native async code and curious with regards to iOS specifically, can something like this be done in {N}?

Objective C:

dispatch_async(dispatch_get_main_queue(), ^{
        ...{N} code
    });

question

Source

NathanWalker

Most helpful comment

For those that might be interested, here's a workaround for dispatch_async: http://nuvio.us/dispatch_async

alexziskind1 on 5 Jul 2016

👍4 ❤3 🎉2

All 13 comments

I think there was a thread that says it cant unfortunately. But maybe im wrong

x4080 on 1 Mar 2016

It doesn't make sense to use dispatch_async directly (nor is it possible) because JavaScript code is always synchronized - the JavaScript block that's executed on the global queue will block the main queue for the duration of its execution, because JavaScript.

If you need to execute code on the main thread, use a promise reaction:

Promise.resolve().then(() => /* this always runs on the main thread */);

Promise reactions are guaranteed to run on the thread that owns the runtime, which is the main thread, unless you edit the platform template to run it on another thread.

If you need to call a native API asynchronously, there's the undocumented async method:

let foo = new XYZNativeClass();
foo.methodThatTakesALongTimeToRunWithArgument.async(foo, [arg1, arg2])
   .then(result => /* do stuff here */);

This works just like the regular apply method on JavaScript functions, except it's only available on native methods and functions and will call the native API on the global queue. The promise continuation is, of course, executed back on the main thread.

fealebenpae on 1 Mar 2016

👍3

@NathanWalker please note the async is iOS only. This hasn't been ported to the Android runtime; so make sure if you are doing cross platform compatible code that you put it into an ios section.