Graft

Description

Graft provides an easy way to map XML and JSON data onto your Ruby classes.

Installation

Stable:

$ sudo gem install graft

Bleeding edge:

$ git clone git://github.com/reagent/graft.git
$ cd graft && rake gem
$ sudo gem install pkg/graft-<version>.gem

Usage

When interacting with APIs, it’s quite often the case that the data returned as part of the response is represented either as XML or JSON. The Graft library makes turning that data into Ruby objects pretty simple. This code was an extraction from my work on both the Fleakr and Etsy gems.

Mapping XML

If you want to use Graft in XML mode, you’ll need to include the right library:

require 'rubygems'
require 'graft/xml'

Once that is set up, you can take an XML string like this:

<rsp>
  <user nsid="3">reagent</user>
  <name>Patrick Reagan</name>
</rsp>

And map it onto a Ruby class:

class User
  include Graft

  attribute :name  
  attribute :username, :from => 'user'
  attribute :id, :from => 'user@nsid', :type => :integer
end

There are a couple of ways to pull this data into the User object. The simplest is from the constructor:

user = User.new(xml)

There is also a populate_from instance method that will do the same:

user = User.new
user.populate_from(xml)

This second method is useful if the data you want in your Ruby object comes from 2 separate XML files. Accessing it is simple:

>> user.name      # => "Patrick Reagan"
>> user.username  # => "reagent"
>> user.id        # => 3

Mapping JSON

The process of mapping JSON is similar to XML, except:

You don’t need to declare the type of the attribute
You need to provide a full path to the JSON value

To get started, include the correct library:

require 'rubygems'
require 'graft/json'

Then for simple JSON data:

{
    "rsp": {
        "user_id": 3,
        "username": "reagent",
        "name": "Patrick Reagan"
    }
}

You can map it in a similar way:

class User
  include Graft

  attribute :name, :from => 'rsp/name'
  attribute :username, :from => 'rsp/username'
  attribute :id, :from => 'rsp/user_id'
end

Again, you can initialize the values from both the constructor:

user = User.new(json)

Or the populate_from method:

user = User.new
user.populate_from(json)

The results are the same:

>> user.name      # => "Patrick Reagan"
>> user.username  # => "reagent"
>> user.id        # => 3

License

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.