afterUpdate() {
    // Handle calling ref function
    let ref = this.ref
    if (ref !== this._lastRef) {
      if (typeof this._lastRef === 'function') {
        this._lastRef.call(null, null)
      }
      if (typeof ref === 'function') {
        ref.call(null, this)
        this._lastRef = ref
      } else {
        this._lastRef = null
      }
    }
  }
Called at the end of an update batch, after all individual properties have been assigned.