WARNING

This package is not yet updated to Block Protocol version 0.2.

React Block Loader

A component which loads a Block Protocol block from a remote URL, and passes on the properties and functions you provide.

Usage

yarn install "react-block-loader"

Pass RemoteBlock (at a minimum) a source url (sourceUrl), the properties the block expects (blockProperties), and functions for it to call (blockProtocolFunctions), as set out in the specification.

1import { RemoteBlock } from "react-block-loader";
2
3const blockDependencies = {
4  react: require("react"),
5  "react-dom": require("react-dom"),
6};
7
8const BlockLoader = ({ blockSourceFolder: string }) => {
9  const [blockMetadata, setBlockMetadata] = useState(null);
10
11  useEffect(() => {
12    fetch(`${blockSourceFolder}/block-metadata.json`)
13      .then((resp) => resp.json())
14      .then(setBlockMetadata);
15  }, [componentId]);
16
17  if (!blockMetadata) {
18    return <div>Loading block metadata...</div>;
19  }
20
21  const blockProperties = {
22    // block's own properties, entityId, linkedEntities, linkGroups, etc
23  };
24
25  const blockProtocolFunctions = {
26    updateEntities: (actions) => {
27      // persist block updates wherever you store them
28    },
29    // more Block Protocol Functions
30  };
31
32  return (
33    <RemoteBlock
34      blockMetadata={blockMetadata}
35      blockProperties={blockProperties}
36      blockProtocolFunctions={blockProtocolFunctions}
37      externalDependencies={blockDependencies}
38      LoadingIndicator={<h1>Optional custom loading indicator</h1>}
39      onBlockLoaded={() =>
40        console.log(`Block with componentId ${componentId} loaded.`)
41      }
42      sourceUrl={`${blockSourceFolder}/${blockMetadata.source}`}
43    />
44  );
45};

Props

name	type	required	default	description
blockMetadata	object	no		the block's block-metadata.json. Will be used to determine Web Component tag names (TBD soon).
blockProperties	object	yes		the block's own properties, and BP-specified properties (e.g. entityId, linkGroups)
crossFrame	boolean	no	false	whether this block should make requests to the parent window for block source
blockProtocolFunctions	object	yes		the functions provided to blocks for reading and editing entity and link data (replaced by graph service in Þ 0.2)
externalDependencies	object	no		libraries which the block depends on but does not include in its package
LoadingIndicator	ReactElement	no	<div>Loading...</div>	an element to display while the block is loading
onBlockLoaded	function	no		a callback, called when the block has been successfully parsed and loaded
sourceUrl	string	yes		the URL to the entry source file for the block

External dependencies

A block may indicate externals in block-metadata.json (docs).

These are libraries the blocks expects the embedding application to supply it. For example, a block may rely on React, but assume that the embedding application will provide it, to save loading it multiple times on a page.

In order to provide blocks with these dependencies, pass an object where the key is <package-name>, and the value is require(<package-name>), e.g.

1const blockDependencies = {
2  react: require("react"),
3  "react-dom": require("react-dom"),
4};

Security

This component automatically fetches, parses, and renders the component from the file at the provided sourceUrl.

You should either make sure you trust the source, or sandbox the component so that it does not matter if it is malicious.

Source Fetching & Caching

Requests are cached by URL, so that each source URL only has to be fetched once, and parsed once (in the same window).

Inside iFrames

Where each RemoteBlock instance is loaded in its own iFrame, you can optionally pass crossFrame=true, and the block will send a message to the parent window requesting the text of the source file. This allows the parent window to keep a cache of text per sourceUrl, which is useful if you have multiple iFrames each loading the same remote block. Each iFrame will still have to parse the source.

See the following exports:

• TextFromUrlRequestMessage – a type for the message request shape
• TextFromUrlResponseMessage – a type for the response
• isTextFromUrlRequestMessage – a typeguard for checking the request is of the type of interest

1// in the parent window, listen for messages requesting text is fetched from a url
2window.addEventListener("message", (requestMessage) => {
3  if (isTextFromUrlRequestMessage(requestMessage)) {
4    // Ideally you would have a Ref to the iFrame in which the component loads,
5    // so that requests to fetch text from other iFrames are not processed.
6    // this function otherwise will fetch any URL requested of it for any iFrame sending the correct message,
7    // and will act with the origin of this window (potentially e.g. sending cookies when fetching the URL)
8    if (source !== frameRef.current?.contentWindow) {
9      return;
10    }
11
12    const { payload, requestId } = requestMessage.data;
13
14    // implement memoizedFetch to cache the text by URL, to avoid fetching it for multiple blocks
15    memoizedFetch(payload.url)
16      .then((resp) => resp.text())
17      .then((text) => {
18        const responseMessage: TextFromUrlResponseMessage = {
19          payload: { data: text },
20          requestId,
21        };
22        requestMessage.source.postMessage(responseMessage, origin);
23      });
24  }
25});

Blocks supported

The component will parse and render blocks which are defined as:

• React components (i.e. a JavaScript file which exports a React component)
• Web Components (i.e. a JavaScript file which exports a custom element class)
• HTML (i.e. an HTML file, which may in turn load other assets)

For JavaScript files, the exported component must be one of:

1. the default export from the file
2. the only named export in the file
3. an export named App

Acknowledgements

The useRemoteBlock hook was adapted from Paciolan/remote-component