Getting Started with ZIO
Include ZIO in your project by adding the following to your build.sbt
file:
libraryDependencies += "dev.zio" %% "zio" % "2.1.9"
If you want to use ZIO streams, you should also include the following dependency:
libraryDependencies += "dev.zio" %% "zio-streams" % "2.1.9"
Main
Your application can extend ZIOAppDefault
, which provides a complete runtime system and allows you to write your whole program using ZIO:
import zio._
import zio.Console._
object MyApp extends ZIOAppDefault {
def run = myAppLogic
val myAppLogic =
for {
_ <- printLine("Hello! What is your name?")
name <- readLine
_ <- printLine(s"Hello, ${name}, welcome to ZIO!")
} yield ()
}
The run
method should return a ZIO value which has all its errors handled,
which, in ZIO parlance, is an unexceptional ZIO value.
One way to do this is to invoke fold
over a ZIO value, to get an unexceptional ZIO value.
That requires two handler functions: eh: E => B
(the error handler) and ah: A => B
(the success handler).
If myAppLogic
fails, eh
will be used to get from e: E
to b: B
;
if it succeeds, ah
will be used to get from a: A
to b: B
.
myAppLogic
, as folded above, produces an unexceptional ZIO value, with B
being Int
.
If myAppLogic
fails, there will be a 1; if it succeeds, there will be a 0.
If you are integrating ZIO into an existing application, using dependency injection, or do not control your main function, then you can create a runtime system in order to execute your ZIO programs:
import zio._
object IntegrationExample {
val runtime = Runtime.default
Unsafe.unsafe { implicit unsafe =>
runtime.unsafe.run(ZIO.attempt(println("Hello World!"))).getOrThrowFiberFailure()
}
}
Ideally, your application should have a single runtime, because each runtime has its own resources (including thread pool and unhandled error reporter).
Console
ZIO provides a module for interacting with the console. You can import the functions in this module with the following code snippet:
If you need to print text to the console, you can use print
and printLine
:
import zio._
// Print without trailing line break
Console.print("Hello World")
// Print string and include trailing line break
Console.printLine("Hello World")
If you need to read input from the console, you can use readLine
:
import zio._
val echo = Console.readLine.flatMap(line => Console.printLine(line))