getRingConnections(ringId, ringIds) {
    let ringConnections = Array();

    for (var i = 0; i < this.ringConnections.length; i++) {
      let rc = this.ringConnections[i];

      for (var j = 0; j < ringIds.length; j++) {
        let id = ringIds[j];

        if (rc.firstRingId === ringId && rc.secondRingId === id || rc.firstRingId === id && rc.secondRingId === ringId) {
          ringConnections.push(rc.id);
        }
      }
    }

    return ringConnections;
  }
Get the ring connections between a ring and a set of rings.

@param {Number} ringId A ring id.
@param {Number[]} ringIds An array of ring ids.
@returns {Number[]} An array of ring connection ids.