REST Basics

Why learn this first?

Before we wire up controllers and services it helps to understand the vocabulary used in REST APIs. Knowing what a resource, route, or HTTP verb means makes the controller code much less mysterious.

Key REST ideas

Resource: A noun that represents something in your system (for example, Task).
Endpoint / Route: The URL you expose for that resource, often combined with an HTTP verb (GET /tasks).
Representation: The JSON payload you send back (or receive) that describes a resource.
Statelessness: Each request contains all info the server needs—no hidden session state.

Common HTTP verbs

Verb	Typical meaning	Example in this project
`GET`	Read data	`GET /tasks` lists tasks
`POST`	Create a new record	`POST /tasks` adds a task
`PATCH`	Update part of a record	`PATCH /tasks/:id` toggles `done`
`DELETE`	Remove a record	`DELETE /tasks/:id` deletes a task

Beginner tip

When you see decorators like @Get() or @Post() in Nest, think of them as aliases for the HTTP verbs above.

Route patterns

Plural nouns keep things consistent: tasks, users, projects.
Use :id in the path to capture a specific record (/tasks/:id).
Query parameters (e.g., /tasks?done=true) are great for filters and pagination.

Request and response flow

Client sends a request using an HTTP verb, URL, optional body, and headers.
Controller decorator catches the request (e.g., @Get('tasks/:id')).
Controller method validates/unwraps parameters and calls the service.
Service performs the database work and returns plain data.
Controller sends a JSON response (Nest handles serialization for you).

Error handling conventions

Return 400 Bad Request when the data is invalid (handled by Zod validation).
Throw 404 Not Found when the requested id does not exist.
Use 500 Internal Server Error for unexpected failures (Nest does this automatically if an uncaught error bubbles up).

With these concepts in mind, you’re ready to build the actual service and controller. Continue to Implement CRUD Service to write the data layer, then wire it up in Controllers & Routes.