README.rdoc
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Toshi MARUYAMA
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r12732 | = AwesomeNestedSet | ||
| Awesome Nested Set is an implementation of the nested set pattern for ActiveRecord models. It is replacement for acts_as_nested_set and BetterNestedSet, but more awesome. | ||||
| Version 2 supports Rails 3. Gem versions prior to 2.0 support Rails 2. | ||||
| == What makes this so awesome? | ||||
| This is a new implementation of nested set based off of BetterNestedSet that fixes some bugs, removes tons of duplication, adds a few useful methods, and adds STI support. | ||||
| == Installation | ||||
| Add to your Gemfile: | ||||
| gem 'awesome_nested_set' | ||||
| == Usage | ||||
| To make use of awesome_nested_set, your model needs to have 3 fields: lft, rgt, and parent_id. | ||||
| You can also have an optional field: depth: | ||||
| class CreateCategories < ActiveRecord::Migration | ||||
| def self.up | ||||
| create_table :categories do |t| | ||||
| t.string :name | ||||
| t.integer :parent_id | ||||
| t.integer :lft | ||||
| t.integer :rgt | ||||
| t.integer :depth # this is optional. | ||||
| end | ||||
| end | ||||
| def self.down | ||||
| drop_table :categories | ||||
| end | ||||
| end | ||||
| Enable the nested set functionality by declaring acts_as_nested_set on your model | ||||
| class Category < ActiveRecord::Base | ||||
| acts_as_nested_set | ||||
| end | ||||
| Run `rake rdoc` to generate the API docs and see CollectiveIdea::Acts::NestedSet for more info. | ||||
| == Callbacks | ||||
| There are three callbacks called when moving a node. `before_move`, `after_move` and `around_move`. | ||||
| class Category < ActiveRecord::Base | ||||
| acts_as_nested_set | ||||
| after_move :rebuild_slug | ||||
| around_move :da_fancy_things_around | ||||
| private | ||||
| def rebuild_slug | ||||
| # do whatever | ||||
| end | ||||
| def da_fancy_things_around | ||||
| # do something... | ||||
| yield # actually moves | ||||
| # do something else... | ||||
| end | ||||
| end | ||||
| Beside this there are also hooks to act on the newly added or removed children. | ||||
| class Category < ActiveRecord::Base | ||||
| acts_as_nested_set :before_add => :do_before_add_stuff, | ||||
| :after_add => :do_after_add_stuff, | ||||
| :before_remove => :do_before_remove_stuff, | ||||
| :after_remove => :do_after_remove_stuff | ||||
| private | ||||
| def do_before_add_stuff(child_node) | ||||
| # do whatever with the child | ||||
| end | ||||
| def do_after_add_stuff(child_node) | ||||
| # do whatever with the child | ||||
| end | ||||
| def do_before_remove_stuff(child_node) | ||||
| # do whatever with the child | ||||
| end | ||||
| def do_after_remove_stuff(child_node) | ||||
| # do whatever with the child | ||||
| end | ||||
| end | ||||
| == Protecting attributes from mass assignment | ||||
| It's generally best to "white list" the attributes that can be used in mass assignment: | ||||
| class Category < ActiveRecord::Base | ||||
| acts_as_nested_set | ||||
| attr_accessible :name, :parent_id | ||||
| end | ||||
| If for some reason that is not possible, you will probably want to protect the lft and rgt attributes: | ||||
| class Category < ActiveRecord::Base | ||||
| acts_as_nested_set | ||||
| attr_protected :lft, :rgt | ||||
| end | ||||
| == Conversion from other trees | ||||
| Coming from acts_as_tree or another system where you only have a parent_id? No problem. Simply add the lft & rgt fields as above, and then run | ||||
| Category.rebuild! | ||||
| Your tree will be converted to a valid nested set. Awesome! | ||||
| == View Helper | ||||
| The view helper is called #nested_set_options. | ||||
| Example usage: | ||||
| <%= f.select :parent_id, nested_set_options(Category, @category) {|i| "#{'-' * i.level} #{i.name}" } %> | ||||
| <%= select_tag 'parent_id', options_for_select(nested_set_options(Category) {|i| "#{'-' * i.level} #{i.name}" } ) %> | ||||
| See CollectiveIdea::Acts::NestedSet::Helper for more information about the helpers. | ||||
| == References | ||||
| You can learn more about nested sets at: http://threebit.net/tutorials/nestedset/tutorial1.html | ||||
| == How to contribute | ||||
| If you find what you might think is a bug: | ||||
| 1. Check the GitHub issue tracker to see if anyone else has had the same issue. | ||||
| https://github.com/collectiveidea/awesome_nested_set/issues/ | ||||
| 2. If you don't see anything, create an issue with information on how to reproduce it. | ||||
| If you want to contribute an enhancement or a fix: | ||||
| 1. Fork the project on GitHub. | ||||
| https://github.com/collectiveidea/awesome_nested_set/ | ||||
| 2. Make your changes with tests. | ||||
| 3. Commit the changes without making changes to the Rakefile, VERSION, or any other files that aren't related to your enhancement or fix | ||||
| 4. Send a pull request. | ||||
| Copyright ©2008 Collective Idea, released under the MIT license | ||||