getRate method

Future<Rate> getRate({ required Currency from, required Currency to, })

Uses caching to avoid fetching the rate every time.

To set the cache duration see cacheDuration.

Implementation

Future<Rate> getRate({required Currency from, required Currency to}) async {
  // Create a fake rate so we get a [_Cache] object with the right id.
  final fakeCache = _Cache(Rate(from, to, 1.0));
  var cache = _cache.lookup(fakeCache);

  if (cache != null &&
      cache.created.add(cacheDuration).isBefore(DateTime.now())) {
    _cache.remove(cache);
    cache = null;
  }
  if (cache == null) {
    final latest = await this.latest(from: from);
    _cache.addAll(latest.map((rate) => _Cache(rate)));
    cache = _cache.lookup(fakeCache);
  }
  return cache!.rate;
}