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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.
Add this line to your application's Gemfile:
gem 'odata'
And then execute:
$ bundle
Or install it yourself as:
$ gem install odata
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.
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.
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",
})
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"
}
}
})
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
Some versions of Microsoft CRM do not support count.
products.count
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)
svc['ProductsSet']['<guid of entity>']
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
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.
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:
- Fork it ( https://github.com/[my-github-username]/odata/fork )
- Create your feature branch (
git checkout -b my-new-feature) - Commit your changes (
git commit -am 'Add some feature') - Push to the branch (
git push origin my-new-feature) - Create a new Pull Request