Reference

Fundamental Concepts

Dagny’s fundamental unit is the resource. A resource is identified by, and can be accessed at, a single HTTP URI. A resource may be singular or plural; for example, /users is a collection of users, and /users/31215 is a single user. See the URI documentation for a detailed schema on Dagny’s URIs and their behavior.

In your code, resources are defined as classes with several actions. An action is essentially a method, routed to based on the request path and method, which is in charge of processing that particular request and returning a response. See the Resources documentation for a concrete explanation of how resources and actions are defined.

Actions themselves are broken up into a main body, and a renderer. The body of the action does the processing—saves/retrieves a record, or perhaps performs some calculation. The renderer is responsible for producing a response. This split allows for modular content negotiation: you can define multiple renderer backends for an action, each of which is associated with a MIME type. These backends will be dispatched to based on what the client has requested; the default is to produce HTML, but you can easily write backends for JSON, XML, RDF, or even PNG if necessary. A full reference on the renderer system can be found in the Renderer documentation.

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