Method addObserver

packages/query-core/src/query.ts:344–353

(observer: QueryObserver<any, any, any, any, any>)

  }

  addObserver(observer: QueryObserver<any, any, any, any, any>): void {
    if (!this.observers.includes(observer)) {
      this.observers.push(observer)

      // Stop the query from being garbage collected
      this.clearGcTimeout()

      this.#cache.notify({ type: 'observerAdded', query: this, observer })
    }
  }

  removeObserver(observer: QueryObserver<any, any, any, any, any>): void {
    if (this.observers.includes(observer)) {