Context

In addition to the data prop, the message list component accepts a context prop, which can be used to pass additional data updates to the ItemContent and the custom headers and footers, if present. The context prop can be anything, but usually it's a key/value object. For example, the message list tutorial uses the context to work with the loading flags and the channel class instance.

note

The VirtuosoMessageList second type parameter is the type of the context prop.

The example below has a header component that accesses the loading flag from the context. The same approach works for all custom components.

Live Editor

interface MessageListContext {
  loading: boolean
}

const Header: VirtuosoMessageListProps<number, MessageListContext>['Header'] = ({ context }) => (
  <div style={{ height: 30, background: 'lightblue' }}>Header - {context.loading ? 'loading' : 'loaded'}</div>
)

function App() {
  const [loading, setLoading] = useState(false)

  return (
    <>
      <button onClick={() => setLoading(!loading)}>Toggle Loading</button>
      <VirtuosoMessageListLicense licenseKey="">
        <VirtuosoMessageList<number, MessageListContext>
          context={{ loading }}
          Header={Header}
          style={{ height: 400 }}
          initialData={Array.from({ length: 100 }, (_, index) => index)}
        />
      </VirtuosoMessageListLicense>
    </>
  )
}

render(<App />)

Result

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