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`launch` vs `async` — what’s the difference in coroutines?

Answer

`launch` starts a coroutine for side-effects and returns a `Job`. `async` returns a `Deferred<T>` for a result and you `await()` it; both should run inside a scope (structured concurrency).

coroutineScope {
  val a = async { 1 }
  val b = async { 2 }
  val sum = a.await() + b.await()
  println(sum)
}

Advanced answer

Deep dive

`launch { ... }`: fire-and-forget *within a scope*; you get a `Job` to cancel/join.
`async { ... }`: you expect a value; you get `Deferred<T>` and should `await()` it.

Exception behavior:

Unhandled exceptions in `launch` cancel the parent scope.
Exceptions in `async` are observed when you `await()` (or when the parent awaits/cancels).

Common pitfalls

Starting `async` and never awaiting it (lost errors / work).
Blocking inside coroutines on the default dispatcher.
Using `GlobalScope` and leaking work beyond lifecycle.

`launch` vs `async` — what’s the difference in coroutines?

Answer

Advanced answer

Deep dive

Common pitfalls

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`launch` vs `async` — what’s the difference in coroutines?

Answer

Advanced answer

Deep dive

Common pitfalls

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