Mojo Example that demos the difference between providing and requesting an interface

examples/indirect_service/README.md

+Indirect Service Demo
+=====================
+
+This demo is intended to highlight the difference between requesting a service
+and providing one. The demo is based on two services: IntegerService and
+IndirectIntegerService.
+
+interface IntegerService {
+  Increment() => (int32 value);
+};
+
+This trival interface just manages a single internal integer that's initialized
+to 0. The Increment() method returns a new value.
+
+interface IndirectIntegerService {
+    Set(IntegerService? service);
+    Get(IntegerService&? service);
+};
+
+This service delegates to the one IntegerService provided by the Set() method.
+Clients use Get() to request a connection to an IntegerService that targets the
+delegate. This is roughly an IntegerService "pointer".
+
+The demo creates a set of threads all of which get their own connection to the
+shared IntegerService via the IndirectIntegerService. The threads all access
+the IntegerService at the same time and then display a little table of the
+results.