Oak

Another radix tree implementation for crystal-lang

Installation

Add this to your application's shard.yml:

dependencies:
  oak:
    github: obsidian/oak

Usage

Building Trees

You can associate one or more payloads with each path added to the tree:

require "oak"

tree = Oak::Tree(Symbol).new
tree.add "/products", :products
tree.add "/products/featured", :featured

results = tree.search "/products/featured"

if result = results.first?
  puts result.payload # => :featured
end

The types allowed for a payload are defined on Tree definition:

tree = Oak::Tree(Symbol).new

# Good, since Symbol is allowed as payload
tree.add "/", :root

# Compilation error, Int32 is not allowed
tree.add "/meaning-of-life", 42

Can combine multiple types if needed:

tree = Oak::Tree(Int32 | String | Symbol).new

tree.add "/", :root
tree.add "/meaning-of-life", 42
tree.add "/hello", "world"

Lookup and placeholders

You can also extract values from placeholders (as named or globbed segments):

tree.add "/products/:id", :product

result = tree.find "/products/1234"

if result
  puts result.params["id"]? # => "1234"
end

Please see Oak::Tree#add documentation for more usage examples.

Optionals

Oak has the ability to add optional paths, i.e. foo(/bar)/:id, which will expand into two routes: foo/bar/:id and foo/:id. In the following example, both results will match and return the same payload.

tree.add "/products(/free)/:id", :product

if result = tree.find "/products/1234"
  puts result.params["id"]? # => "1234"
  puts result.payload # => :product
end

if result = tree.find "/products/free/1234"
  puts result.params["id"]? # => "1234"
  puts result.payload # => :product
end

Caveats

Multiple results

Due the the dynamic nature of this radix tree, and to allow for a more flexible experience for the implementer, the .search method will return a list of results. Alternatively, you can interact with the results by providing a block.

matching_payload = nil
@tree.search(path) do |result|
  unless matching_payload
    context.request.path_params = result.params
    matching_payload = result.payloads.find do |payload|
      payload.matches_constraints? context.request
    end
    matching_payload.try &.call(context)
  end
end

Multiple Leaves

In order to allow for a more flexible experience for the implementer, this implementation of radix will not error if a multiple payloads are added at the same path/key. You can either call the .payload method to grab the first payload, or you can use the .payloads method, which will return all the payloads.

Shared Keys

When designing and adding paths to a Tree, please consider that two different named parameters cannot share the same level:

tree.add "/", :root
tree.add "/:post", :post
tree.add "/:category/:post", :category_post # => Radix::Tree::SharedKeyError

This is because different named parameters at the same level will result in incorrect params when lookup is performed, and sometimes the value for post or category parameters will not be stored as expected.

To avoid this issue, usage of explicit keys that differentiate each path is recommended.

For example, following a good SEO practice will be consider /:post as absolute permalink for the post and have a list of categories which links to a permalink of the posts under that category:

tree.add "/", :root
tree.add "/:post", :post                    # this is post permalink
tree.add "/categories", :categories         # list of categories
tree.add "/categories/:category", :category # listing of posts under each category

Roadmap

• Support multiple payloads at the same level in the tree.
• Return multiple matches when searching the tree.
• Support optionals in the key path.
• Overcome shared key caveat.

Implementation

This project has been inspired and adapted from: luislavena

Contributing

1. Fork it ( https://github.com/obsidian/oak/fork )
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create a new Pull Request

Contributors

• Jason Waldrip - creator, maintainer