Reflection

lib/reflect/ provides first-class reflection over classes, methods, fields, constructors, and annotations.

Types

Type	File	Role
Class	lib/reflect/Class.mt	A reflected class declaration.
Method	lib/reflect/Method.mt	A reflected method on a class.
Field	lib/reflect/Field.mt	A reflected field.
Constructor	lib/reflect/Constructor.mt	A reflected constructor.
Annotation	lib/reflect/Annotation.mt	A reflected annotation instance.
Library	lib/reflect/Library.mt	Loaded .mtcLib introspection.
Modifier	lib/reflect/Modifier.mt	Access modifier flags.

Looking up a Class

import * from "lib/reflect/Class.mt";

Class c = Class::forName("Service");
print(c.getName());

Listing Methods

import * from "lib/reflect/Class.mt";
import * from "lib/reflect/Method.mt";

Class c = Class::forName("Service");
ArrayList<Method> methods = c.getDeclaredMethods();
for (Method m : methods) {
    print(m.getName() + " : " + m.getReturnType().getName());
}

Reading Annotations

Only @Retention(RUNTIME) annotations survive into runtime metadata.

import * from "lib/reflect/Class.mt";
import * from "lib/reflect/Method.mt";
import * from "lib/reflect/Annotation.mt";

Class c = Class::forName("Service");
Method m = c.getDeclaredMethod("ping", 0);
Annotation? t = m.getAnnotation("Timeout");
if (t != null) {
    print(t.getInt("ms"));
}

Invocation

Constructor ctor = c.getConstructor(0);
Object[] args = new Object[0];
Object instance = ctor.newInstance(args);

Method m = c.getDeclaredMethod("greet", 0);
m.invoke(instance, args);

newInstance and invoke are instance methods — call them with . on a Constructor or Method value returned from reflection. Both take a Object[] of arguments.

See Also

• Annotations
• Architecture / VM — class metadata in bytecode.