1 files changed, 47 insertions, 0 deletions
diff --git a/lib/erb/def_method.rb b/lib/erb/def_method.rb
new file mode 100644
index 0000000000..aee989a926
--- /dev/null
+++ b/lib/erb/def_method.rb
@@ -0,0 +1,47 @@
+# frozen_string_literal: true
+#--
+# ERB::DefMethod
+#
+# Utility module to define eRuby script as instance method.
+#
+# === Example
+#
+# example.rhtml:
+#   <% for item in @items %>
+#   <b><%= item %></b>
+#   <% end %>
+#
+# example.rb:
+#   require 'erb'
+#   class MyClass
+#     extend ERB::DefMethod
+#     def_erb_method('render()', 'example.rhtml')
+#     def initialize(items)
+#       @items = items
+#     end
+#   end
+#   print MyClass.new([10,20,30]).render()
+#
+# result:
+#
+#   <b>10</b>
+#
+#   <b>20</b>
+#
+#   <b>30</b>
+#
+module ERB::DefMethod
+  # define _methodname_ as instance method of current module, using ERB
+  # object or eRuby file
+  def def_erb_method(methodname, erb_or_fname)
+    if erb_or_fname.kind_of? String
+      fname = erb_or_fname
+      erb = ERB.new(File.read(fname))
+      erb.def_method(self, methodname, fname)
+    else
+      erb = erb_or_fname
+      erb.def_method(self, methodname, erb.filename || '(ERB)')
+    end
+  end
+  module_function :def_erb_method
+end