Tensho · August 27, 2018 20:15 · Aug 27, 2018
diff --git a/count_ruby_instances_by_class_1.rb b/count_ruby_instances_by_class_1.rb
@@ -0,0 +1,28 @@
+class A
+  def self.count
+    @count
+  end
+
+  def self.count=(v)
+    @count = v
+  end
+
+  def initialize
+    self.class.count += 1
+  end
+end
+
+class B < A
+  @count = 0
+end
+
+class C < A
+  @count = 0
+end
+
+B.new
+C.new
+C.new
+
+B.count #=> 1
+C.count #=> 2
diff --git a/count_ruby_instances_by_class_2.rb b/count_ruby_instances_by_class_2.rb
@@ -0,0 +1,10 @@
+A = Class.new
+B = Class.new(A)
+C = Class.new(A)
+
+B.new
+C.new
+C.new
+
+ObjectSpace.each_object(B).count #=> 1
+ObjectSpace.each_object(C).count #=> 2