Refit is a lightweight, type-safe REST library that empowers .NET developers to create HTTP API clients in a declarative way, reducing redundant code and streamlining your programming process.

While Refit is highly advantageous for simplifying API client development, it's not without its caveats.

Understanding both its powerful features and limitations can help developers optimize their use of this tool.

Installation and Setup

Refit is easily accessible via the NuGet package manager. You can add it to your project by running the following command:

Install-Package Refit

After installation, you're ready to start building your API client.

API Interface Definition

With Refit, API endpoints are declared as interfaces. This approach ensures type safety and aligns with best practices of object-oriented programming. For instance, suppose we have a web service that allows managing artists for a music streaming service. We could define the endpoints like this:

public interface IMusicApi
{
    [Get("/artists")]
    Task<List<Artist>> GetArtists();

    [Get("/artists/{id}")]
    Task<Artist> GetArtist(int id);

    [Post("/artists")]
    Task<Artist> CreateArtist([Body] Artist artist);

    [Put("/artists/{id}")]
    Task UpdateArtist(int id, [Body] Artist artist);

    [Delete("/artists/{id}")]
    Task DeleteArtist(int id);
}

With this interface, we can perform CRUD operations on Artist objects. Each method corresponds to a specific HTTP verb, and parameters translate to parts of the URL or the request body.

Refit Implementation

With our API interface in place, we can now let Refit implement it for us. Using the RestService class, we can construct an instance that provides an implementation of our interface:

var musicApi = RestService.For<IMusicApi>("http://api.example.com");

This instance allows us to make HTTP requests, such as retrieving a list of artists:

var artists = await musicApi.GetArtists();

.NET Core supports registering via HttpClientFactory

services
    .AddRefitClient<IMusicApi>()
    .ConfigureHttpClient(c => c.BaseAddress = new Uri("http://api.example.com"));

Behind the scenes, Refit automatically translates these method calls into corresponding HTTP requests, and automatically deserializes the returned JSON into the defined objects.
 

Advanced Features: Custom Converters, Authentication and More

Refit offers flexibility in various aspects. You can plug in custom converters if the standard JSON.NET serialization doesn't suit your needs. Similarly, for APIs requiring authentication, Refit allows integrating various authentication methods. You can use HttpClient message handlers to attach auth tokens to your requests or integrate more complex authentication flows.
 

Handling Errors

Refit throws an ApiException when a response indicates an HTTP error status. This exception provides crucial details like the status code and error content, facilitating error handling and debugging:

try
{
    var artist = await musicApi.GetArtist(123);
}
catch (ApiException ex)
{
    Console.WriteLine($"An error occurred: {ex.StatusCode}");
}

Limitations of Refit

While Refit is a powerful and convenient tool, it has certain limitations and considerations. First, as Refit is built on top of HttpClient, it inherits some of HttpClient's limitations. For instance, control over timeouts, authentication, and cookie handling still needs to be implemented by you.

Moreover, Refit defaults to using JSON.NET as the serialization tool, but this can be configured to use other serialization tools. If you have special serialization requirements, you might need extra configurations.

Additionally, Refit is most suited for standard RESTful APIs. If your API has non-standard features, such as unique URL structures or request formats, you might need to implement these using other means.
  

Conclusion

Refit is an invaluable tool in the .NET ecosystem, especially for developers working extensively with REST APIs. It encourages cleaner code, enhances productivity, and reduces the likelihood of errors.

With it, you can focus more on your business logic and less on the nitty-gritty details of HTTP communication.

Thanks for reading, and happy coding🤘!
 

Reference: https://github.com/reactiveui/refit