Extract default behavior into a separate module

Ditch 1.9 support in the process

.travis.yml

@@ -1,4 +1,3 @@
 rvm:
-  - 1.9
   - 2.0
   - 2.1

adequate_exposure.gemspec

@@ -12,7 +12,7 @@ Gem::Specification.new do |spec|
   spec.test_files   = spec.files.grep(/\Aspec\//)
   spec.require_path = "lib"
 
-  spec.required_ruby_version = ">= 1.9.3"
+  spec.required_ruby_version = "~> 2.0"
 
   spec.add_dependency "railties",      "~> 4.0"
   spec.add_dependency "activesupport", "~> 4.0"

lib/adequate_exposure.rb

@@ -6,6 +6,7 @@ module AdequateExposure
   autoload :Exposure,   "adequate_exposure/exposure"
   autoload :Attribute,  "adequate_exposure/attribute"
   autoload :Context,    "adequate_exposure/context"
+  autoload :Behavior,   "adequate_exposure/behavior"
   autoload :Flow,       "adequate_exposure/flow"
 
   ActiveSupport.on_load :action_controller do

lib/adequate_exposure/behavior.rb

@@ -0,0 +1,56 @@
+module AdequateExposure
+  module Behavior
+    def fetch
+      computed_scope = scope(model)
+      instance = id ? find(id, computed_scope) : build(build_params, computed_scope)
+      decorate(instance)
+    end
+
+    def id
+      params_id_key_candidates.each do |key|
+        value = params[key]
+        return value if value.present?
+      end
+
+      nil
+    end
+
+    def scope(model)
+      model
+    end
+
+    def model
+      name.to_s.classify.constantize
+    end
+
+    def find(id, scope)
+      scope.find(id)
+    end
+
+    def build(params, scope)
+      scope.new(params)
+    end
+
+    def decorate(instance)
+      instance
+    end
+
+    def build_params
+      if controller.respond_to?(params_method_name, true) && !get_request?
+        controller.send(params_method_name)
+      else
+        {}
+      end
+    end
+
+    protected
+
+    def params_id_key_candidates
+      [ "#{model.name.underscore}_id", "#{name}_id", "id" ].uniq
+    end
+
+    def model_param_key
+      model.name.underscore
+    end
+  end
+end

lib/adequate_exposure/exposure.rb

@@ -6,10 +6,8 @@ def self.expose!(*args, &block)
       new(*args, &block).expose!
     end
 
-    def initialize(controller, name, *args, &block)
+    def initialize(controller, name, fetch_block=nil, **options, &block)
       @controller = controller
-      options = args.extract_options!
-      fetch_block = args.pop
       @options = options.with_indifferent_access.merge(name: name)
 
       merge_lambda_option :fetch, fetch_block if fetch_block

lib/adequate_exposure/flow.rb

@@ -8,57 +8,16 @@ def initialize(controller, options)
       @name = options.fetch(:name)
     end
 
-    %w[fetch find build build_params scope model id decorate].each do |method_name|
-      define_method method_name do |*args|
-        ivar_name = "@#{method_name}"
-        return instance_variable_get(ivar_name) if instance_variable_defined?(ivar_name)
-        instance_variable_set(ivar_name, handle_action(method_name, *args))
+    def method_missing(name, *args, &block)
+      if respond_to_missing?(name)
+        handle_flow_method(name, *args, &block)
+      else
+        super
       end
     end
 
-    protected
-
-    def default_fetch
-      computed_scope = scope(model)
-      instance = id ? find(id, computed_scope) : build(build_params, computed_scope)
-      decorate(instance)
-    end
-
-    def default_id
-      params_id_key_candidates.each do |key|
-        value = params[key]
-        return value if value.present?
-      end
-
-      nil
-    end
-
-    def default_scope(model)
-      model
-    end
-
-    def default_model
-      name.to_s.classify.constantize
-    end
-
-    def default_find(id, scope)
-      scope.find(id)
-    end
-
-    def default_build(params, scope)
-      scope.new(params)
-    end
-
-    def default_decorate(instance)
-      instance
-    end
-
-    def default_build_params
-      if controller.respond_to?(params_method_name, true) && !get_request?
-        controller.send(params_method_name)
-      else
-        {}
-      end
+    def respond_to_missing?(method_name, include_private = false)
+      Behavior.method_defined?(method_name) || super
     end
 
     private
@@ -73,15 +32,17 @@ def params_method_name
       options.fetch(:build_params_method){ "#{name}_params" }
     end
 
-    def handle_action(name, *args)
-      if options.key?(name)
-        handle_custom_action(name, *args)
-      else
-        send("default_#{name}", *args)
+    def handle_flow_method(name, *args, &block)
+      fetch_ivar name do
+        if options.key?(name)
+          handle_options_override(name, *args, &block)
+        else
+          handle_default_flow_method(name, *args, &block)
+        end
       end
     end
 
-    def handle_custom_action(name, *args)
+    def handle_options_override(name, *args)
       value = options[name]
 
       if Proc === value
@@ -92,12 +53,20 @@ def handle_custom_action(name, *args)
       end
     end
 
-    def params_id_key_candidates
-      [ "#{model.name.underscore}_id", "#{name}_id", "id" ].uniq
+    def handle_default_flow_method(name, *args, &block)
+      method = Behavior.instance_method(name)
+      method.bind(self).call(*args, &block)
     end
 
-    def model_param_key
-      model.name.underscore
+
+    def fetch_ivar(name)
+      ivar_name = "@#{name}"
+
+      if instance_variable_defined?(ivar_name)
+        instance_variable_get(ivar_name)
+      else
+        instance_variable_set(ivar_name, yield)
+      end
     end
   end
 end