lab19: init

lab19/record.rb

@@ -0,0 +1,37 @@
+=begin
+Ruby provides a number of hooks that allow a developer
+to change the behavior of objects.
+The design is similar to JavaScript's Proxies (both are
+metaobject protocols), but unlike proxies,
+these hooks apply for all objects.
+
+The most famous of these is method_missing,
+based on Smalltalk's doesNotUnderstand:.
+=end
+
+# Consider Ruby on Rails.
+# With Rails you refer to a record's fields by their names.
+# We will (crudely) simulate that.
+class Record
+  def initialize fields
+    @fields = fields
+  end
+
+  def method_missing m, *args
+    meth_name = m.to_s
+    if (meth_name.end_with?("=")) then
+      @fields[meth_name.chop] = args[0]
+    else
+      @fields[meth_name]
+    end
+  end
+end
+
+r = Record.new ({ 'fname' => 'Rick', 'lname' => 'Grimes', 'profession' => 'Police Officer' })
+puts r.profession
+r.profession = 'Zombie hunter'
+puts r.profession
+
+# Ruby has const_missing as well, which works in a similar manner, except that it applies
+# to missing class constants
+