Advanced topics Reflection

Reflection

Reflection in Klyn starts with type(...) and expands into metadata about members, inheritance, annotations, generics, and more. This is especially useful for tooling, tests, and framework-style code.

Acquiring a Type

import klyn.math

r = Rational(1, 3)
metadata = type(r)
print(metadata.name)
print(metadata.fullName)

Kind Flags

interface Worker:
    public run() as Void

metadata = type(Worker)
assert metadata.isInterface
assert metadata.isAbstract

Reflection exposes whether a type is public, abstract, final, native, an interface, an enum, or an annotation.

Inspecting Members

import klyn.math

metadata = type(Rational(1, 3))
attrs = metadata.getAttributes()
props = metadata.getProperties()
methods = metadata.getMethods()

You can inspect declared members, retrieve a member by name, and choose whether inherited members should be included.

Dynamic Invocation

import klyn.reflection

method = Application.type.getMethod("time")
if method is Invocable<Object>:
    result = method.invoke([] as Object[])
    print(result)

Invocable<R> is the common reflection-level contract for functions obtained dynamically, methods, and constructors. Its arguments use Object[] because their signature is runtime metadata. For ordinary callbacks and lambda parameters, prefer the complete structural form (P1, P2) -> R, which the compiler can validate statically. The two models are intentionally distinct and no implicit conversion erases a structural signature into an Invocable<R>.

Property Capabilities

class CredentialSink:
    public writeonly property credential as String

sink = CredentialSink()
property = type(sink).getProperty("credential")

assert property.isWriteonly
assert not property.isReadonly
property.setValue(sink, "temporary secret")

Reflected properties preserve their source contract. isReadonly identifies a getter-only property and isWriteonly identifies a setter-only property. Calling setValue() on a readonly property or getValue() on a write-only property raises TypeError; reflection never bypasses accessor visibility.

Generic Reflection

import klyn.collections

metadata = type(List<Int>)
print(metadata.isGenericInstantiation)
print(metadata.genericParameterCount)
print(metadata.genericParameterNames())

Annotations Through Reflection

annotation Audited:
    pass

metadata = type(Audited)
print(metadata.isAnnotation)

Reflection can also expose annotations attached to types and members, which is how test frameworks and metadata-driven tooling discover annotated declarations.