The Future of Functional Programming- ZIO

Reading Time: 3 minutes

In the current scenario, lots of companies try to adopt functional programming or some elements of the functional programming paradigm, so they want to choose to take what’s best available in both worlds (functional & object-oriented programming). But, this mindset of people is slowly changing now, with the introduction of ZIO. Big companies like Apple, DHL, and are adopting ZIO in their production apps.

Let’s dive into some details of Zio.

What is Zio?

ZIO is a purely functional, type-safe, a composable library for asynchronous, concurrent programming in Scala. It is perfect for mid to large-scale projects that require a lot of concurrency and speed. Zio solves complex, modern business problems using simple, testable, and composable code. It is a functional effect system in Scala

What is the functional effect?

An effect is a description of an action that will be coming into use when an evaluation happens.  Every effect can be an operation itself, but a functional effect is a description of that operation.

For example, in Scala, the code println(“Hello, Scala!”) is an effect that prints the “Hello, Scala!” message to the console. The println function is of type Any => Unit. It returns the Unit, so it is a statement. But in ZIO, Console.printLine(“Hello, ZIO!”) is a functional effect of printing “Hello, ZIO!” on the console. It is a description of such an operation. Console.printLine is a function of type Any => ZIO[Any, IOException, Unit]. It returns the ZIO data type, which is the description of printing the message to the console.

Benefits of Zio-

For Bussiness-

  • High-performance Mean much better performance. It helps in building scalable applications with 100x the performance of Scala’s Future.
  • Resource-safe Zio helps in building apps that never leak resources (including threads!), even when they fail.
  • Type-safe The full power of ZIO’s type-safe Scala compiler can catch bugs at compile time..
  • Concurrent – Easily build concurrent apps without deadlocks, race conditions, or complexity.
  • Asynchronous Write sequential code that looks the same whether it’s asynchronous or synchronous.

For Developers-

  • ZIO allows a developer to build highly composable applications from small building blocks, thanks to its purely-functional design.
  • It is excellent for introducing developers to functional programming in Scala, without the need to learn a lot of jargon and hard-to-understand concepts that are typical of other libraries like cats or Scalaz.
  • ZIO makes applications more testable, so it’s a lot easier to write unit tests.

Basic program

The basic building block of ZIO applications is the ZIO[R, E, A] type, which describes effective computation, where:

  • R is the type of environment to run the effect.
  • E is the type of error that may be produced by the effect.
  • A is the type of value that may be produced by the effect.

Our application can be divided into smaller modules and any dependencies are expressed as constraints for the environment type R. First of all, we have to add the dependency on ZIO to SBT build:

libraryDependencies += "dev.zio" %% "zio" % "1.0.12"

Basic Program in Scala

object Demo 
    def main(args: Array[String]) 
        println("Hello World!") 

Basic Program in Zio-

object Main extends zio.App {
  val myApp: ZIO[Console, IOException, Unit] =
    putStrLn("Hello, World!")

  override def run(args: List[String]): URIO[zio.ZEnv, ExitCode] = myApp.exitCode


In this blog, we have learned about basic things related to Zio. We also get to know about the functional effect, benefits of zio, and basic program of zio.

Scala Future