mattconnolly · April 1, 2014 03:17 · Apr 1, 2014 · Apr 1, 2014 · Apr 1, 2014
diff --git a/gistfile1.rb b/gistfile1.rb
@@ -2,10 +2,12 @@ module Let
 
   def let(name, &block)
     ivar = "@#{name}".to_sym
-    unless instance_variable_defined?(ivar)
+    if instance_variable_defined?(ivar)
+      instance_variable_get(ivar)
+    else
       instance_variable_set(ivar, instance_eval(&block))
     end
-    instance_variable_get(ivar)
+
   end
 
 end

diff --git a/gistfile1.txt → gistfile1.rb b/gistfile1.txt → gistfile1.rb
diff --git a/gistfile1.txt b/gistfile1.txt
@@ -0,0 +1,24 @@
+module Let
+
+  def let(name, &block)
+    ivar = "@#{name}".to_sym
+    unless instance_variable_defined?(ivar)
+      instance_variable_set(ivar, instance_eval(&block))
+    end
+    instance_variable_get(ivar)
+  end
+
+end
+
+class Thing
+  include Let
+
+  def result
+    let(:result) { some_expensive_calculation_that_could_return_nil }
+  end
+end
+
+t = Thing.new
+t.result #=> calculated result that could be nil
+t.result #=> cached result that could be nil
+