Class QueryClient

packages/query-core/src/queryClient.ts:79–1093

 * ```
 */
export class QueryClient {
  #queryCache: QueryCache
  #mutationCache: MutationCache
  #defaultOptions: DefaultOptions
  #queryDefaults: Map<string, QueryDefaults>
  #mutationDefaults: Map<string, MutationDefaults>
  #mountCount: number
  #unsubscribeFocus?: () => void
  #unsubscribeOnline?: () => void

  constructor(config: QueryClientConfig = {}) {
    this.#queryCache = config.queryCache || new QueryCache()
    this.#mutationCache = config.mutationCache || new MutationCache()
    this.#defaultOptions = config.defaultOptions || {}
    this.#queryDefaults = new Map()
    this.#mutationDefaults = new Map()
    this.#mountCount = 0
  }

  /**
   * Called by a framework adapter's `QueryClientProvider`-equivalent when it mounts, to start
   * listening for focus/online events and resume paused mutations. Ref-counted via an internal
   * mount count, so nested or multiple providers sharing the same `QueryClient` don't tear down
   * the shared listeners until the last one unmounts.
   */
  mount(): void {
    this.#mountCount++
    if (this.#mountCount !== 1) return

    this.#unsubscribeFocus = focusManager.subscribe(async (focused) => {
      if (focused) {
        await this.resumePausedMutations()
        this.#queryCache.onFocus()
      }
    })
    this.#unsubscribeOnline = onlineManager.subscribe(async (online) => {
      if (online) {
        await this.resumePausedMutations()
        this.#queryCache.onOnline()
      }
    })
  }

  /**
   * The inverse of {@link QueryClient#mount} — called by a framework adapter's
   * `QueryClientProvider`-equivalent when it unmounts. Only tears down the focus/online
   * listeners once the mount count returns to `0`.
   */
  unmount(): void {
    this.#mountCount--
    if (this.#mountCount !== 0) return

    this.#unsubscribeFocus?.()
    this.#unsubscribeFocus = undefined

    this.#unsubscribeOnline?.()
    this.#unsubscribeOnline = undefined
  }