Rust oData is library for building OData REST services in Rust. This library is referenced and utilized by the ConnectFour project in the game_server repository for service generation.

The online documentation for rust-odata can be found here.

OData (Open Data Protocol) is an ISO/IEC approved, OASIS standard that defines a set of best practices for building and consuming RESTful APIs. OData helps you focus on your business logic while building RESTful APIs without having to worry about the various approaches to define request and response headers, status codes, HTTP methods, URL conventions, media types, payload formats, query options, etc. OData also provides guidance for tracking changes, defining functions/actions for reusable procedures, and sending asynchronous/batch requests. [1]

The library can be used to build REST API based using the Entity Data Model. EntityTypes and EntitySets are declared using macros which provide additional information used to generate metadata and create resource paths. For instance, we can declare a Game EntityType

// Creates a new Game struct and generates serveral methods used internally
defEntity!(Game(keys => id) {
    id: Int64,
    width: Int64,
    height: Int64,
    k: Int16,
    curr_player: Int16,
    status: String,
    board: String
});

and and EntitySet Games which consists of these types.

/// Declares Games as an EntitySet containing entities of type Game. Once added to
/// the model, it will be reachable via <...>/Games(I) 
defEntitySet!(Games, Game);

Now we can implemented CRUD operations for our sevice via the EntitySet trait:

 fn create(&self, value: serde_json::Value) -> Res { ... } 
 fn read(&self, key: String) -> Res { ... } 
 fn read_list(&self) -> Res { ... } 
 fn update ...
 fn delete ...

The EntitySet trait provides a default implementation for these methods, meaning that we only need to directly implement those that we plan on using. Lastly we need to instantiate the model using our EntitySet (here we only have one), as well as declare the name of our service and start listening for requests.

let model = ModelBuilder::new("connect_four.svc")
    .add(Games::declare())
    .build()
    
let svc = ServiceBuilder::new("api")
    .add(model)
    .build();

svc.start();

Now our clients can access our API using <hostname:port>/api/connect_four.svc to, for example, get a list of games by going to <hostname:port>/api/connect_four.svc/Games