More on #UWPCommunityToolkit CacheBase #uwpdev

In the first version of UWP Community Toolkit, we only had ImageCache which had its origin in Windows App Studio. A few issues were raised to optimise it and one mentioned extensible cache that can be used to create any case.

FileCache, ImageCache, VideoCache, JsonCache.. you name it.. Yesterday I mentioned CacheBase. FileCache and ImageCache that ship with UWP Community Toolkit are implementations of CacheBase by giving it a specific type.

Today I had to implement ability to pull configuration settings from our server. I tried using current prod version of FileCache but my implementation was somewhat wrong there. It would try to create File from Stream and return null and then fail internally (fixed in current dev branch) however I needed something today. Enter ConfigCache.. well JsonCache really

public class ConfigCache : CacheBase<ConfigurationSetting>
{
    JsonSerializer jsonSerializer = new JsonSerializer();

    /// <summary>
    /// Private singleton field.
    /// </summary>
    private static ConfigCache _instance;

    /// <summary>
    /// Gets public singleton property.
    /// </summary>
    public static ConfigCache Instance => _instance ?? (_instance = new ConfigCache() { MaintainContext = false });

    protected override async Task<ConfigurationSetting> InitializeTypeAsync(StorageFile baseFile)
    {
        using (var stream = await baseFile.OpenStreamForReadAsync())
        {
            return InitializeTypeAsync(stream);
        }
    }

    protected override Task<ConfigurationSetting> InitializeTypeAsync(IRandomAccessStream stream)
    {
        var config = InitializeTypeAsync(stream.AsStream());
        return Task.FromResult<ConfigurationSetting>(config);
    }

    private ConfigurationSetting InitializeTypeAsync(Stream stream)
    {
        var reader = new StreamReader(stream);

        using (var jsonReader = new JsonTextReader(reader))
        {
            return jsonSerializer.Deserialize<ConfigurationSetting>(jsonReader);
        }
    }
}

In this case I am using a specific type to deserialise json to. How do I use it ?

ConfigCache.Instance.CacheDuration = TimeSpan.FromDays(1);

this.ConfigurationSettings = await ConfigCache.Instance.GetFromCacheAsync(new Uri(urlPath));

This would ensure that if configuration is older than a day, it will be downloaded again. Either way the caller will get deserialised data.