Re: [Vala] Need help in async methods

[Jiří Janoušek <janousek jiri gmail com>]

Hello Marcin,

When I need a sync wrapper around async method, I generally do
something like this:

public bool dosomething() {
  var result = false;
  var loop = new MainLoop();

  dosomething_async.begin((obj, res) => {
    result = dosomething_async.end(res);
    loop.quit();
  });

  loop.run(); // wait until async method finishes
  return result;
}

Best,

Jiri Janousek

On Sat, Jan 16, 2016 at 3:56 PM, marcin saepia net <marcin saepia net> wrote:
> Hello,
>
> I am trying to create a function is synchronous and block for the outer
> world, but internally
>
> a) does nothing unless certain callback is called
> b) does not block mainloop
>
> Something like synchronous HTTP calls in libsoup - you do request, the
> execution if caller is stopped until it's done, the result is just returned
> but internally it does asynchronous operations and does not block the whole
> program.
>
>
> I read tutorial and samples but I still struggle to find the valid pattern,
> I came to the point that looks more less like this:
>
> public class MyClass : Object {
>   private OtherClass other;
>   private SourceFunc other_callback;
>   private bool       other_result;
>
>
>   public bool dosomething() {
>     // What should I put here to block callee and call dosomething_async
> asynchronously?
>   }
>
>
>   public async bool dosomething_async() {
>     this.other = new OtherClass();
>     this.other.finished.connect(on_other_finished);
>
>     this.other_callback = dosomething_async.callback;
>     yield;
>     // Now everything except the callee should continue execution
>     // unless OtherClass sends us a callback
>   }
> }
>
>
> private void on_other_finished(bool result) {
>   // Task is finished, should unblock dosomething();
>   this.other_result = result;
>   this.other_callback();
> }
>
>
> int main(string[] argv) {
>   var instance = new MyClass();
>   var result = instance.dosomething(); // <-- this should block
>
>   return 0;
> }
>
>
> Thank you for your help
>
> m.
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