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Scala Reflect

Reflection without runtime reflection. Macros describe your types at compile time; at runtime you read descriptors and call generated accessors, on the JVM and in Scala.js alike.

1.1.4Current release
JVM ยท Scala.jsRuns on
Scala 3.3Language version
MITLicense

Installation

A cross-built artifact. With sbt 2, %% adds the right platform suffix for the JVM and for Scala.js.

sbt
libraryDependencies += "com.anjunar" %% "scala-reflect" % "1.1.4" // sbt 1, Scala.js: libraryDependencies += "com.anjunar" %%% "scala-reflect" % "1.1.4"

Describe a case class

reflect expands to a ClassDescriptor at compile time. The values below are read from it while this page renders.

descriptor.typeName
demo.Person
descriptor.simpleName
Person
descriptor.isCaseClass
true
descriptor.constructors.head.parameterNames
name, age
descriptor.getProperty("age").map(_.propertyType.typeName)
Some(scala.Int)
scala
package demo case class Person(name: String, age: Int) import reflect.macros.ReflectMacros val descriptor = ReflectMacros.reflect[Person]
01 / Compile time

Metadata from macros

The structure of a type is read by the compiler, not discovered at runtime. Nothing is guessed and nothing is missing on Scala.js.

02 / Typed access

Accessors instead of Method.invoke

Getters and setters are generated code. A read-only property gets no setter at all.

03 / One model

The same descriptors everywhere

Server and browser share one model of your types. scalajs-ui and json-mapper build on it.

Contents

From a descriptor to a registry

Describe types, access their properties, then register them to look them up by name at runtime.

DescribingClass descriptorsProperties, constructors, base types and annotations of a class.PropertiesType, access, visibility and annotations of one property.Constructors and parametersPrimary and secondary constructors, parameters with defaults.AnnotationsScala and Java annotations as values, with their arguments.Type descriptorsParameterized types, type variables and arrays.GenericsType parameters with bounds and applied type arguments.
AccessAccessorsTyped getters and setters generated from a selector.Properties for APIsProperty handles for schemas, forms and query builders.Creating instancesCase classes from arguments, other classes from factories.
RuntimeRegistryThe global runtime registry: look up, create and check by name.Class loadersScoped registries with parents, subtype queries and resources.InheritanceBase types, subtype lookups and creating by type name.
In practiceA form from a descriptorInput fields generated from writable properties, live.A typed filter APINamed property handles for queries, live.
ReferenceAPIMacros, descriptors and runtime types at a glance.