Entities

Let's start coding the app by defining the Task entity class.

The Task entity class will be used:

• As a model class for client-side code
• As a model class for server-side code
• By remult to generate API endpoints, API queries, and database commands

The Task entity class we're creating will have an auto-generated id field, a title field, a completed field and an auto-generated createdAt field. The entity's API route ("tasks") will include endpoints for all CRUD operations.

Define the Model

1. Create a shared folder under the src folder. This folder will contain code shared between frontend and backend.

2. Create a file Task.ts in the src/shared/ folder, with the following code:

// src/shared/Task.ts

import { Entity, Fields } from "remult"

@Entity("tasks", {
  allowApiCrud: true
})
export class Task {
  @Fields.cuid()
  id = ""

  @Fields.string()
  title = ""

  @Fields.boolean()
  completed = false

  @Fields.createdAt()
  createdAt?: Date
}

3. In the server's api module, register the Task entity with Remult by adding entities: [Task] to an options object you pass to the remultExpress() middleware:

// src/server/api.ts

import { remultExpress } from "remult/remult-express"
import { Task } from "../shared/Task"

export const api = remultExpress({
  entities: [Task]
})

The @Entity decorator tells Remult this class is an entity class. The decorator accepts a key argument (used to name the API route and as a default database collection/table name), and an options argument used to define entity-related properties and operations, discussed in the next sections of this tutorial.

To initially allow all CRUD operations for tasks, we set the option allowApiCrud to true.

The @Fields.cuid decorator tells Remult to automatically generate a short random id using the cuid library. This value can't be changed after the entity is created.

The @Fields.string decorator tells Remult the title property is an entity data field of type String. This decorator is also used to define field-related properties and operations, discussed in the next sections of this tutorial and the same goes for @Fields.boolean and the completed property.

The @Fields.createdAt decorator tells Remult to automatically generate a createdAt field with the current date and time.

TIP

For a complete list of supported field types, see the Field Types section in the Remult documentation.

Test the API

Now that the Task entity is defined, we can start using the REST API to query and add a tasks.

1. Open a browser with the url: http://localhost:3002/api/tasks, and you'll see that you get an empty array.

2. Use curl to POST a new task - Clean car.

curl http://localhost:3002/api/tasks -d "{\"title\": \"Clean car\"}" -H "Content-Type: application/json"

3. Refresh the browser for the url: http://localhost:3002/api/tasks and see that the array now contains one item.

4. Use curl to POST a few more tasks:

curl http://localhost:3002/api/tasks -d "[{\"title\": \"Read a book\"},{\"title\": \"Take a nap\", \"completed\":true },{\"title\": \"Pay bills\"},{\"title\": \"Do laundry\"}]" -H "Content-Type: application/json"

• Note that the POST endpoint can accept a single Task or an array of Tasks.

5. Refresh the browser again, to see that the tasks were stored in the db.

Wait, where is the backend database?

While remult supports many relational and non-relational databases, in this tutorial we start by storing entity data in a backend JSON file. Notice that a db folder has been created under the root folder, with a tasks.json file containing the created tasks.

Display the Task List

Let's start developing the web app by displaying the list of existing tasks in a React component.

Replace the contents of src/App.tsx with the following code:

// src/App.tsx

import { useEffect, useState } from "react"
import { remult } from "remult"
import { Task } from "./shared/Task"

const taskRepo = remult.repo(Task)

export default function App() {
  const [tasks, setTasks] = useState<Task[]>([])

  useEffect(() => {
    taskRepo.find().then(setTasks)
  }, [])
  return (
    <div>
      <h1>Todos</h1>
      <main>
        {tasks.map(task => {
          return (
            <div key={task.id}>
              <input type="checkbox" checked={task.completed} />
              {task.title}
            </div>
          )
        })}
      </main>
    </div>
  )
}

Here's a quick overview of the different parts of the code snippet:

• taskRepo is a Remult Repository object used to fetch and create Task entity objects.
• tasks is a Task array React state to hold the list of tasks.
• React's useEffect hook is used to call the Remult repository's find method to fetch tasks from the server, once when the React component is loaded.

After the browser refreshes, the list of tasks appears.