/// <summary>
/// Works like SelectMany, but memoizes selector calls. In addition, it
/// guarantees that no more than 'maxConcurrent' selectors are running
/// concurrently and queues the rest. This is very important when using
/// web services to avoid potentially spamming the server with hundreds
/// of requests.
///
/// This overload is useful when making the same web service call in
/// several places in the code, to ensure that all of the code paths are
/// using the same cache.
/// </summary>
/// <param name="existingCache">An already-configured ObservableAsyncMRUCache.</param>
/// <returns>An Observable representing the flattened results of the
/// cache selector.</returns>
public static IObservable <TRet> CachedSelectMany <T, TRet>(this IObservable <T> This, ObservableAsyncMRUCache <T, TRet> existingCache)
{
return(This.SelectMany(existingCache.AsyncGet));
}
/// <summary>
/// Works like SelectMany, but memoizes selector calls. In addition, it
/// guarantees that no more than 'maxConcurrent' selectors are running
/// concurrently and queues the rest. This is very important when using
/// web services to avoid potentially spamming the server with hundreds
/// of requests.
/// </summary>
/// <param name="selector">A selector similar to one you would pass as a
/// parameter passed to SelectMany. Note that similarly to
/// ObservableAsyncMRUCache.AsyncGet, a selector must return semantically
/// identical results given the same key - i.e. it must be a 'function' in
/// the mathematical sense.</param>
/// <param name="maxCached">The number of items to cache. When this limit
/// is reached, not recently used items will be discarded.</param>
/// <param name="maxConcurrent">The maximum number of concurrent
/// asynchronous operations regardless of key - this is important for
/// web-based caches to limit the number of concurrent requests to a
/// server. The default is 5.</param>
/// <param name="scheduler"></param>
/// <returns>An Observable representing the flattened results of the
/// selector.</returns>
public static IObservable <TRet> CachedSelectMany <T, TRet>(this IObservable <T> This, Func <T, IObservable <TRet> > selector, int maxCached = 50, int maxConcurrent = 5, IScheduler scheduler = null)
{
var cache = new ObservableAsyncMRUCache <T, TRet>(selector, maxCached, maxConcurrent, null, scheduler);
return(This.SelectMany(cache.AsyncGet));
}