ZIOConfigNarrowOps

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1. final def !=(arg0: Any): Boolean

   

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2. final def ##(): Int

   

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3. final def ==(arg0: Any): Boolean

   

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4. final def asInstanceOf[T0]: T0

   

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5. def getClass(): Class[_ <: AnyVal]

   

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6. final def isInstanceOf[T0]: Boolean

   

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7. def narrow[B](f: (A) ⇒ B)(implicit arg0: Tag[B], ta: Tag[A]): ZLayer[R, E, B]

   

   In bigger apps you can have a lot of components and, consequently - a lot of configuration fields.

   In bigger apps you can have a lot of components and, consequently - a lot of configuration fields. It's not ideal to pass around the whole configuration object as a dependency for all of those components: this way you break the separation of concerns principle. Component should be aware only about dependencies it cares about and uses somehow.

   So to avoid that and do it in an ergonomic way, there's a narrow syntax extension for ZLayer, available under import zio.config.syntax._. In the below example, we use both zio-config-magnolia and zio-config-typesafe module inorder to have automatic derivation as well as read/write HOCON structure.

   import zio._
   import zio.config._, typesafe._, syntax._, magnolia.DeriveConfigDescriptor
   
   trait Endpoint
   trait Repository
   
   case class AppConfig(api: ApiConfig, db: DbConfig)
   case class DbConfig (url: String,    driver: String)
   case class ApiConfig(host: String,   port: Int)
   
   val configDescription = DeriveConfigDescriptor.descriptor[AppConfig]
   
   // components have only required dependencies
   val endpoint: ZLayer[Has[ApiConfig], Nothing, Has[Endpoint]]    = ZLayer.fromService(_ => new Endpoint {})
   val repository: ZLayer[Has[DbConfig], Nothing, Has[Repository]] = ZLayer.fromService(_ => new Repository {})
   
   val cfg = TypesafeConfig.fromResourcePath(configDescription)
   
   cfg.narrow(_.api) >>> endpoint // narrowing down to a proper config subtree
   cfg.narrow(_.db) >>> repository

8. def toString(): String

   

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