Simple OData Library for Ruby
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README.md

OData

THIS PROJECT NEEDS HELP: We need additional maintainers and contributors; please open an issue if you are interested in helping.

BETA QUALITY, at best — You've been warned

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The OData gem provides a simple wrapper around the OData API protocol. It has the ability to automatically inspect compliant APIs and expose the relevant Ruby objects dynamically. It also provides a set of code generation tools for quickly bootstrapping more custom service libraries.

Installation

Add this line to your application's Gemfile:

gem 'odata'

And then execute:

$ bundle

Or install it yourself as:

$ gem install odata

Usage

Services & the Service Registry

The OData gem provides a number of core classes, the two most basic ones are the OData::Service and the OData::ServiceRegistry. The only time you will need to worry about the OData::ServiceRegistry is when you have multiple OData services you are interacting with that you want to keep straight easily. The nice thing about OData::Service is that it automatically registers with the registry on creation, so there is no manual interaction with the registry necessary.

To create an OData::Service simply provide the location of a service endpoint to it like this:

OData::Service.open('http://services.odata.org/OData/OData.svc')

You may also provide an options hash after the URL. It is suggested that you supply a name for the service via this hash like so:

OData::Service.open('http://services.odata.org/OData/OData.svc', name: 'ODataDemo')

This one call will setup the service and allow for the discovery of everything the other parts of the OData gem need to function. The two methods you will want to remember from OData::Service are #service_url and #name. Both of these methods are available on instances and will allow for lookup in the OData::ServiceRegistry, should you need it.

Using either the service URL or the name provided as an option when creating an OData::Service will allow for quick lookup in the OData::ServiceRegistry like such:

OData::ServiceRegistry['http://services.odata.org/OData/OData.svc']
OData::ServiceRegistry['ODataDemo']

Both of the above calls would retrieve the same service from the registry. At the moment there is no protection against name collisions provided in OData::ServiceRegistry. So, looking up services by their service URL is the most exact method, but lookup by name is provided for convenience.

Authentication

When authenticating with your service you can set parameters to the Typhoeus gem which uses libcurl. Use the :typhoeus option to set your authentication.

For example using ntlm authentication:

conn = OData::Service.open('http://services.odata.org/OData/OData.svc', {
    name: 'ODataDemo',
    typhoeus: {
      username: 'username',
      password: 'password',
      httpauth: :ntlm
    }
})

For more authentication options see libcurl or typhoeus.

Metadata File

Typically the metadata file of a service can be quite large. You can speed your load time by forcing the service to load the metadata from a file rather than a URL. This is only recommended for testing purposes, as the metadata file can change.

conn = OData::Service.open('http://services.odata.org/OData/OData.svc', {
    name: 'ODataDemo',
    metadata_file: "metadata.xml",
})

Headers

You can set the headers with the :typhoeus param like so:

conn = OData::Service.open('http://services.odata.org/OData/OData.svc', {
    name: 'ODataDemo',
    typhoeus: {
      headers: {
        "DataServiceVersion" => "2.0"
      }
    }
})

Entity Sets

When it comes to reading data from an OData service the most typical way will be via OData::EntitySet instances. Under normal circumstances you should never need to worry about an OData::EntitySet directly. For example, to get an OData::EntitySet for the products in the ODataDemo service simply access the entity set through the service like this:

svc = OData::Service.open('http://services.odata.org/OData/OData.svc')
products = svc['ProductsSet'] # => OData::EntitySet

OData::EntitySet instances implement the Enumerable module, meaning you can work with them very naturally, like this:

products.each do |entity|
  entity # => OData::Entity for type Product
end

You can get a list of all your entity sets like this:

svc.entity_sets

Count

Some versions of Microsoft CRM do not support count.

products.count

Collections

You can you the following methods to grab a collection of Entities:

products.each do |entity|
  ...
end

The first entity object returns a single entity object.

products.first

first(x) returns an array of entity objects.

products.first(x)

Find a certain Entity

svc['ProductsSet']['<guid of entity>']

Entities

OData::Entity instances represent individual entities, or records, in a given service. They are returned primarily through interaction with instances of OData::EntitySet. You can access individual properties on an OData::Entity like so:

product = products.first # => OData::Entity
product['Name']  # => 'Bread'
product['Price'] # => 2.5 (Float)

Individual properties on an OData::Entity are automatically typecast by the gem, so you don't have to worry about too much when working with entities. The way this is implemented internally guarantees that an OData::Entity is always ready to save back to the service or OData::EntitySet, which you do like so:

svc['Products'] << product # Write back to the service
products << product        # Write back to the Entity Set

You can get a list of all your entities like this:

svc.entity_types

Entity Properties

Reading, parsing and instantiating all properties of an entity can add up to a significant amount of time, particularly for those entities with a large number of properties. To speed this process up all properties are lazy loaded. Which means it will store the name of the property, but will not parse and instantiate the property until you want to use it.

You can find all the property names of your entity with

product.property_names

When you want to grab the value of the property like this

product["Name"]

or

product.get_property("Name")

It will parse and instantiate the property if it hasnt done so yet.

Queries

OData::Query instances form the base for finding specific entities within an OData::EntitySet. A query object exposes a number of capabilities based on the System Query Options provided for in the OData specification. Below is just a partial example of what is possible:

query = svc['Products'].query
query.where(query[:Price].lt(15))
query.where(query[:Rating].gt(3))
query.limit(3)
query.skip(2)
query.order_by("Name")
query.select("Name,CreatedBy")
query.inline_count
results = query.execute
results.each {|product| puts product['Name']}

The process of querying is kept purposely verbose to allow for lazy behavior to be implemented at higher layers. Internally, OData::Query relies on the OData::Query::Criteria for the way the where method works. You should refer to the published RubyDocs for full details on the various capabilities:

Contributing

  1. Fork it ( https://github.com/[my-github-username]/odata/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