Defining a Getter

As their name implies, in a Joystick app, getters are the part of our API responsible for getting data. Getters can retrieve data from any data source (e.g., a third-party API or a static file), though, typically your data source will be one of the databases you've connected to your app.

As an example, we're going to wire up a getter that returns the test data we created earlier via our fixture. In the /api folder created for you when you ran joystick create, we want to create another folder books. Inside of that folder, we want to create a file getters.js:

const getters = {
  books: {
    get: () => {
      return process.databases.mongodb.collection('books').find().toArray();
      // PostgreSQL
      // return process.databases.postgresql.query(`SELECT * FROM books`);
    },
  },
};

export default getters;

Getters are defined on an object (typically, we expect to have more than one getter for a data source/topic). In the file above, we've created a variable getters that's assigned an object containing another object books.

That name, books, is the name of our getter (behind the scenes, Joystick will automatically create an HTTP GET route at /api/_getters/books for this). Finally, we export getters as the default export from our file with export default getters (you'll see how this comes into play in Registering Your API).

On that books object, we've defined a single method get() which is responsible for performing the work to get the data for our getter. The get() function is data-source agnostic, meaning, we can get our data from wherever we'd like. For this example, we're going to retrieve the books that we inserted into our database using our fixture earlier.

Because we configured our Joystick app to connect to MongoDB earlier (or, if you preferred, PostgreSQL), behind the scenes when we started our app, Joystick automatically connected the driver for MongoDB and made it globally accessible in our app at process.databases.mongodb (or process.databases.postgresql for a PostgreSQL database). Here, we tap into that driver and run a .find() query on our books collection to retrieve the books we created with our fixture.

Later, we'll see how to call to our books getter from a component and render our data on the client (browser).