QueryRequest.js

import {normalizeQueryEncoding} from './util';

// An QueryRequest is used to represent a RethinkDB query that a component is
// subscribed to. It should be used for values in the object returned from the
// observe() function of components that use the provided mixin. See Mixin.js
// for the API.
//
// QueryRequests have have 3 required properties.
// * query:     the RethinkDB query to run
// * changes:   boolean specifying whether to subscribe to the realtime
//              changefeed too
// * initial:   value to be returned before the query finishes loading
// * transform: function applied after the query finishes loading
//
// Here is a simple example of an QueryRequest that a component might use in
// its observe() function:
//   new QueryRequest({
//     query: r.table('turtles'),
//     changes: true,
//     initial: [],
//     transform: (rows) => { // array-to-object, using id as key for O(1) lookup
//       rows.reduce((prev, cur) => {
//        prev[cur.id] = cur
//        prev
//      }, {})
//    }
//   })
export class QueryRequest {
  constructor({query, changes, initial, transform}) {
    this.query = normalizeQueryEncoding(query);
    this.changes = changes;
    this.initial = initial;
    this.transform = transform;
  }

  // Convert the QueryRequest into a string that can be used as a
  // deterministic lookup key in an object. The key should be identical for two
  // QueryRequests that need access to the same data.
  toStringKey() {
    return JSON.stringify({
      query: this.query.build(),
      changes: this.changes,
    });
  }
}