1 files changed, 52 insertions, 0 deletions
diff --git a/activesupport/lib/active_support/core_ext/module/delegation.rb b/activesupport/lib/active_support/core_ext/module/delegation.rb
index ee8adae1cb..b927059c6b 100644
--- a/activesupport/lib/active_support/core_ext/module/delegation.rb
+++ b/activesupport/lib/active_support/core_ext/module/delegation.rb
@@ -156,4 +156,56 @@ class Module
       end
     end
   end
+
+  def delegate!(*methods)
+    ActiveSupport::Deprecation.warn('Delegating to non-public methods is deprecated.', caller)
+
+    options = methods.pop
+    unless options.is_a?(Hash) && to = options[:to]
+      raise ArgumentError, "Delegation needs a target. Supply an options hash with a :to key as the last argument (e.g. delegate :hello, :to => :greeter)."
+    end
+    prefix, to, allow_nil = options[:prefix], options[:to], options[:allow_nil]
+
+    if prefix == true && to.to_s =~ /^[^a-z_]/
+      raise ArgumentError, "Can only automatically set the delegation prefix when delegating to a method."
+    end
+
+    method_prefix =
+      if prefix
+        "#{prefix == true ? to : prefix}_"
+      else
+        ''
+      end
+
+    file, line = caller.first.split(':', 2)
+    line = line.to_i
+
+    methods.each do |method|
+      method = method.to_s
+
+      if allow_nil
+        module_eval(<<-EOS, file, line - 2)
+          def #{method_prefix}#{method}(*args, &block)        # def customer_name(*args, &block)
+            if #{to} || #{to}.respond_to?(:#{method})         #   if client || client.respond_to?(:name)
+              #{to}.__send__(:#{method}, *args, &block)       #     client.__send__(:name, *args, &block)
+            end                                               #   end
+          end                                                 # end
+        EOS
+      else
+        exception = %(raise "#{self}##{method_prefix}#{method} delegated to #{to}.#{method}, but #{to} is nil: \#{self.inspect}")
+
+        module_eval(<<-EOS, file, line - 1)
+          def #{method_prefix}#{method}(*args, &block)        # def customer_name(*args, &block)
+            #{to}.__send__(:#{method}, *args, &block)         #   client.__send__(:name, *args, &block)
+          rescue NoMethodError                                # rescue NoMethodError
+            if #{to}.nil?                                     #   if client.nil?
+              #{exception}                                    #     # add helpful message to the exception
+            else                                              #   else
+              raise                                           #     raise
+            end                                               #   end
+          end                                                 # end
+        EOS
+      end
+    end
+  end
 end