update readme

README.md

@@ -20,7 +20,123 @@ Or install it yourself as:
 
 ## Usage
 
-TODO: Write usage instructions here
+If you have complex model class it can be split into clear model class and actions. For example, `Post` model
+
+```ruby
+class Post
+  scope :search, ->(title) { where tile: title }
+  scope :page, ->(page, size) { ... }
+
+  def add_tags(tags)
+    ...
+  end
+
+  def remove_tags(tags)
+    ...
+  end
+end
+```
+
+can be split into pretty `Post` model and actions: `searchable`, `pageable`, `tagable`
+
+```ruby
+class Post
+  acts_as_searchable :title, ignorecase: true
+  acts_as :pageable, :tagable
+end
+```
+
+Searchable action
+
+```ruby
+module Actions
+  module Searchable
+    extend ActiveSupport::Concern
+
+    included do
+      scope :search, ->(text) do
+        actions[:searchable].fields.each do |field, options|
+          # field is title
+          # options is { ignorecase: true }
+          ...
+        end
+      end
+    end
+  end
+end
+```
+
+Pageable action
+
+```ruby
+module Actions
+  module Pageable
+    extend ActiveSupport::Concern
+
+    included do
+      scope :page, ->(page, size) { ... }
+    end
+  end
+end
+```
+
+Tagable action
+
+```ruby
+module Actions
+  module Tagable
+    def add_tags(tags)
+      ...
+    end
+
+    def remove_tags(tags)
+      ...
+    end
+  end
+end
+```
+
+Action is a ruby module and can be included into model class with DSL `acts_as` very easy
+
+```ruby
+acts_as :action1, :action2, ...
+```  
+
+or with fields and options
+
+```ruby
+acts_as_action1 :field1, :field2, option1: 1, options2: 2
+```  
+
+Inside action module you can get fields and options through actions method.
+
+```ruby
+module Actions
+  module Action1
+    # class method actions
+
+    # get action fields
+    actions(:action1).field.keys
+
+    # iterate each field with options
+    actions(:action1).field.each do |field, options|
+      ...
+    end
+
+    def do_somthing
+      # instance method actions do the same
+    end
+  end
+end
+```
+
+ActionModel works with rails folder structure. Actions can be stored into some folders:
+
+* local action folder path is `/app/model/post`
+* global action folder path is `/app/models/actions` and `/lib/actions`
+
+Local action has more priority then global. When actions with the same name are stored in both folder, then local action will be included.
+It helps to override some action for specific model.
 
 ## Contributing