Custom File Elements

In Getting Started we used an AttachmentBlock Preset for uploaded files.

This guide explains how the AttachmentBlock Preset works and how to create or customize one.

In this example, we'll add a contentType property and show it in the attachment block.

Custom File Type

🌞 Even if you aren't using TypeScript, we recommend reading this section. You can probably follow the meaning of the type declarations (e.g. originKey: string means the originKey property takes a string type value).

Here is the type for the AttachmentBlockElement.

export type AttachmentBlockElement = {
  type: "attachment-block"
  originKey: string // ✅ `originKey` is the only required property
  filename: string
  bytes: number
  children: [{ text: "" }]
}

This Element has a type of attachment-block. Since it is a void Element, it has children of [{ text: "" }] (a requirement for void Elements).

It also has an originKey which is a string. This is the only required property for a File Element.

The other properties filename and bytes are custom properties on the AttachmentBlockElement. Let's modify it to add a contentType property and also change the type of the Element to custom-attachment-block.

export type CustomAttachmentBlockElement = {
  type: "custom-attachment-block"
  originKey: string
  filename: string
  bytes: number
  contentType: string // ✅ Add a `content-type` property
  children: [{ text: "" }]
}

Custom File Component

This is a version of the AttachmentBlock Component used for rendering but with the styling removed.

export function AttachmentBlock({
  attributes,
  element,
  children,
}: RenderElementPropsFor<AttachmentBlockElement>) {
  // ✅ NOTE: This `userOrigin` hook returns an `Origin` object
  //    which we'll talk about more below.
  const origin = useOrigin(element.originKey)

  return (
    <div {...attributes}>
      <div contentEditable={false}>
        {/* ✅ This is where we show info about this attachment */}
        <div>
          <a href={origin.url} target="_blank" download>
            {element.filename}
          </a>
        </div>
        {/* ✅ This displays a progress bar or an error bar */}
        <StatusBar origin={origin} width={192} height={16}>
          {element.bytes} bytes
        </StatusBar>
      </div>
      {children}
    </div>
  )
}

Like any Element Component it has {...attributes} and {children}. We also set contentEditable={false} on the <div> that surrounds the attachment information so the user can't edit it.

The useOrigin Hook

Something new that we haven't seen before is the useOrigin hook.

const origin = useOrigin(element.originKey)

The useOrigin hook takes the originKey (a string) from the element and returns an Origin object. This Origin object has:

  • a url which is a string

  • a status which can be "uploading", "error or "complete"

  • And other properties depending on the status like the upload progress or an error message

To learn more about these properties of Origin, read the API Reference to Origin.

In the AttachmentBlock code above we use the origin.url as the href for the link.

<a href={origin.url} target="_blank" download>
  {element.filename}
</a>

The StatusBar Component

In the AttachmentBlock Component is a StatusBar Component:

<StatusBar origin={origin} width={192} height={16}>
  {element.bytes} bytes
</StatusBar>

What the StatusBar displays depends on the status of the origin:

  • If the origin status is uploading it shows an upload progress bar

  • If the origin status is error it shows a red bar that says Upload Failed

  • If the origin status is complete it shows the children of the StatusBar component. In the code above, it shows the size of the file in bytes.

In the code above, when the upload is complete, it displays the number of bytes in the file.

Customizing the Component

Let's add our custom contentType property to a CustomAttachmentBlock:

export function CustomAttachmentBlock({
  attributes,
  element,
  children,
}: RenderElementPropsFor<CustomAttachmentBlockElement>) {
  const origin = useOrigin(element.originKey)

  return (
    <div {...attributes}>
      <div contentEditable={false}>
        <div>
          <a href={origin.url} target="_blank" download>
            {element.filename}
          </a>
        </div>
        <StatusBar origin={origin} width={192} height={16}>
          {/* ✅ Show the file's contentType after `bytes` */}
          {element.bytes} bytes, {element.contentType}
        </StatusBar>
      </div>
      {children}
    </div>
  )
}

When the file is finished uploading, our new Attachment will show the content type after the number of bytes in the uploaded file.

Custom createFileElement

When a user uploads a file, if it's an image, it is handled by the createImageFileElement function passed to withPortive if there is one. If the file is not an image or there is no createImageFileElement function defined, then it is handled by the createFileElement function.

Here's how it is used in Getting Started:

const editor = withPortive(reactEditor, {
  createImageFileElement: createImageBlock,
  createFileElement: createAttachmentBlock,
  // ...
})

Here's the createAttachmentBlock method passed into the createFileElement option:

export function createAttachmentBlock(
  e: OnUploadEvent
): AttachmentBlockElement {
  return {
    originKey: e.originKey,
    type: "attachment-block",
    filename: e.file.name,
    bytes: e.file.size,
    children: [{ text: "" }],
  }
}

We can see that it passes the originKey to the Element. It also takes properties from e.file which is a File object to fill the bytes and filename property of the AttachmentBlockElement.

Let's modify it to set the contentType as well:

export function createCustomAttachmentBlock(
  e: OnUploadEvent
): CustomAttachmentBlockElement {
  return {
    originKey: e.originKey,
    type: "custom-attachment-block",
    filename: e.file.name,
    bytes: e.file.size,
    // ✅ Set the `contentType` from the `File` object
    contentType: e.file.type,
    children: [{ text: "" }],
  }
}

Here's the full source code...

import {
  CreatedImageFileElementEvent,
  RendeElementPropsFor,
  HostedImage,
} from "slate-portive"

export type CustomAttachmentBlockElement = {
  type: "custom-attachment-block"
  originKey: string
  filename: string
  bytes: number
  contentType: string // ✅ Add a `content-type` property
  children: [{ text: "" }]
}


export function createCustomAttachmentBlock(
  e: OnUploadEvent
): CustomAttachmentBlockElement {
  return {
    originKey: e.originKey,
    type: "custom-attachment-block",
    filename: e.file.name,
    bytes: e.file.size,
    // ✅ Set the `contentType` from the `File` object
    contentType: e.file.type,
    children: [{ text: "" }],
  }
}

export function CustomAttachmentBlock({
  attributes,
  element,
  children,
}: RenderElementPropsFor<CustomAttachmentBlockElement>) {
  const origin = useOrigin(element.originKey)

  return (
    <div {...attributes}>
      <div contentEditable={false}>
        <div>
          <a href={origin.url} target="_blank" download>
            {element.filename}
          </a>
        </div>
        <StatusBar origin={origin} width={192} height={16}>
          {element.bytes} bytes,
          {/* ✅ Show the file's contentType */}
          {element.contentType}
        </StatusBar>
      </div>
      {children}
    </div>
  )
}
}
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