nitg & lib: intro `Finalizable` to be called when an object is freed

[nit.git] / lib / standard / gc.nit

diff --git a/lib/standard/gc.nit b/lib/standard/gc.nit
index 1ffab48..acee1f6 100644 (file)
--- a/lib/standard/gc.nit
+++ b/lib/standard/gc.nit
@@ -17,3 +17,22 @@ redef class Sys
        # Initiate a garbage collection
        fun force_garbage_collection is intern
 end
+
+# An object needing finalization
+#
+# Sub-classes of `Finalizable` must no have cycles, or else they will not be
+# liberated. For this reason, it is recommended to sub-class `Finalizable`
+# only on simple objects directly managing a limited resource. This use case
+# is common when wrapping an extern instance with a standard object.
+class Finalizable
+
+       # Liberate any resources held by `self` before the memory holding `self` is freed
+       #
+       # This method is invoked by the GC during a garbage collection when `self`
+       # is no longer referenced. It can also be called by the user. Its implementation
+       # must be planned accordingly and ensure that it may be invoked more than once.
+       #
+       # The object are finialized in a topological order, it is safe for this method
+       # to use attributes of this instances.
+       fun finalize do end
+end