Function createExtension

Extensions offer a way to provide custom implementations of certain parts of the CameraKit SDK.

This enables more advanced use-cases, in which the default behavior of the SDK is substantially altered. For example, replacing the default implementation that loads remote lens assets with a custom implementation that returns different assets based on some business logic within the application.

An extension is implemented as a PartialContainer – a collection of factory functions, each with its own dependencies, which each provide some "Service". A Service can be of any type, and the CameraKit SDK defines its own Services, some of which can be overridden by providing a custom implementation of the type via an extension.

Here's an example of how extensions might be used:

import { bootstrapCameraKit, createExtension, remoteMediaAssetLoaderFactory } from '@snap/camera-kit'

const myCustomRemoteAssetLoader = Injectable(
  remoteMediaAssetLoaderFactory.token,
  [remoteMediaAssetLoaderFactory.token] as const,
  (defaultLoader: AssetLoader): AssetLoader => {
    return async (asset, lens) => {
      if (lens?.id === MY_SPECIAL_LENS) {
        return (await fetch('my/asset.glb')).arrayBuffer()
      }
      return defaultLoader(asset, lens)
    }
  },
)

const myExtension = createExtension().provides(myCustomRemoteAssetLoader);
const cameraKit = bootstrapCameraKit(config, container => container.provides(myExtension));
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This also enables greater modularity – the person/team creating the extension can do so in their own package, which could be shared by many applications that all require the same functionality.