createComputedCache • tldraw Docs

Create a computed cache that works with any StoreObject (store or object containing a store). This is a standalone version of Store.createComputedCache that can work with multiple store instances.

function createComputedCache<
  Context extends StoreObject<any>,
  Result,
  Record extends
    StoreObjectRecordType<Context> = StoreObjectRecordType<Context>,
>(
  name: string,
  derive: (context: Context, record: Record) => Result | undefined,
  opts?: CreateComputedCacheOpts<Result, Record>
): {
  get(context: Context, id: IdOf<Record>): Result | undefined
}

Example

const expensiveCache = createComputedCache(
  'expensiveData',
  (context: { store: Store<Book> }, book: Book) => {
    return performExpensiveCalculation(book)
  }
)

// Use with different store instances
const result1 = expensiveCache.get(storeObject1, bookId)
const result2 = expensiveCache.get(storeObject2, bookId)

Parameters

Name	Description
`name`	`string` A unique name for the cache (used for debugging)
`derive`	`( context: Context, record: Record ) => Result \| undefined` Function that derives a value from the context and record
`opts`	`CreateComputedCacheOpts<Result, Record>` Optional configuration for equality checks

Returns

{
  get(context: Context, id: IdOf<Record>): Result | undefined
}

A cache that can be used with multiple store instances