How await works. Support for async function

[onmyway133]

Hi, cool library 👍

I was reading through https://github.com/malcommac/Hydra/blob/master/Sources/Hydra/Await.swift#L109

// Create a semaphore to block the execution of the flow until
		// the promise is fulfilled or rejected
		let semaphore = DispatchSemaphore(value: 0)

so we're turning async code -> sync code by blocking the current thread?

Also, it would be cooler if there's an example project 😉

[malcommac]

Hi, thank you. :)
Await is a way to block the execution of current caller thread, resolve passed promise in another queue then resume the execution. In fact you are telling "await the fulfill of a promise". Promise will be resolved in another thread but the queue called by await is blocked.
This allows you to express a sync code in a sync manner.
Howewer if you don't need it you can still use Promise in classic way.
I'll also add async shortcut soon.

[malcommac]

An example of await can be found in README. I'll make a project with examples later during development; meanwhile you can take a look at unit tests in order to see how it works.

[onmyway133]

@malcommac Hi, got it. Thanks 👍

[tomquist]

This should be mentioned in the README that await simply blocks the current thread. I first thought await magically worked similar to the C# await keyword and couldn't believe that this was even possible in Swift until I looked into the code to discover that it just blocks.

[onmyway133]

@tomquist yeah, I had the same thought too

[malcommac]

Yeah I think you are right; I've missed to explicitly add it to the documentation.
Here are the commits which fixes it 01ee6c5 and 09a3afa (both in 0.9.2 branch)

I've also added async operator which can works in two ways: to create a Promise or just execute a block of code.

I'm also looking a way to make it easier to write; if you have some suggestions I'll be more than happy to implement them.