Use start

The start function in each container defines its initialization logic. Whether you’re loading data, setting up configurations, or performing calculations, start manages the container’s setup when it’s ready to launch. In this guide, we’ll cover:

We’ll explore:

• Synchronous and Asynchronous Execution: How to use start for both synchronous and asynchronous tasks.
• Return Value: The structure of the object returned by start, including the api key.

Using start effectively allows containers to initialize with necessary data and handle any required asynchronous operations.

Examples

Example 1: Synchronous Execution in start

For simple tasks that don’t involve asynchronous operations, start can be used synchronously. Here’s an example of a container that initializes with basic configuration data:

import { createContainer, compose } from '@grlt-hub/app-compose';

const configContainer = createContainer({
  id: 'config',
  start: () => {
    console.log('Configuration loaded');
    return { api: { theme: 'dark' } };
  },
});

await compose.up([dataContainer]);

Expected Result

The configContainer initializes and logs its status:

Configuration loaded

Example 2: Asynchronous Execution in start

If start needs to perform asynchronous tasks, such as fetching data from an API, you can make it asynchronous by defining it as an async function. Here’s an example:

import { createContainer, compose } from '@grlt-hub/app-compose';

const dataContainer = createContainer({
  id: 'data',
  start: async () => {
    const response = await fetch('/api/data');
    const data = await response.json();
    console.log('Data loaded:', data);
    return { api: { data } };
  },
});

await compose.up([dataContainer]);

Expected Result

The dataContainer waits until the data is loaded and then completes its initialization:

Data loaded: { ... }

Example 3: Return Value of start

The start function should always return an object with an api key, which provides data or functions that might be needed elsewhere in the application. Here’s an example of how to structure this return value:

const settingsContainer = createContainer({
  id: 'settings',
  start: () => {
    return { api: { setting1: true, setting2: 'value' } };
  },
});

Expected Result

In this example, settingsContainer returns configuration settings within the api key, making them available for use.

{ setting1: true, setting2: 'value' }

Summary

In this guide, we explored how to use the start function to initialize containers. Key takeaways include:

• Synchronous and Asynchronous Execution: start can handle both simple, synchronous tasks and more complex asynchronous operations, such as data fetching. To execute asynchronous tasks, simply define start as an async function.
• Return Value: The start function should always return an object containing an api key. This api key provides data or functionality that may be needed elsewhere in the application, helping to maintain a consistent structure across containers.

By effectively using start, you can set up containers with the required data and manage initialization processes, whether they are synchronous or asynchronous.