REQUESTS - Offline Availability

Offline Availability

• Have you ever found a case where you have a cache, but it just doesn’t care about the user’s current network status?
• Have you ever wanted to ensure data is available for your app the next time it launches, but the user is disconnected?

When you are building a mobile app, you need to consider offline availability. This is especially true for apps that are used in the field or in areas where network connectivity is spotty.

Note

Offline availability is installed by default with the UseMaui setup.

The offline availability middleware is used as part of the default middleware installed by Shiny.Mediator.Maui. Like most other middleware, you simply need to mark your IRequestHandler.Handle method(s) with the attribute [Offline]

The offline attribute also takes a boolean - true = keep the response across app restarts, false = only keep the response in meory with the current app session.

Obviously, offline only works for request handlers with a return value.

Fine grained control over offline data is available via Request Keys

Request Handler Example

public class MyRequestHandler : IRequestHandler<MyRequest, IReadOnlyList<MyThingData>>
{
    [Offline(true)]
    public async Task<IReadOnlyList<MyThingData>> Handle(MyRequest request, CancellationToken cancellationToken)
    {
        // each return will overwrite the previous return value
    }
}

Controlling HOW the offline data is stored

Often, there are times you want to store data based on the parameter arguments within your request. Trying to build these keys for you can be a bit tricky, so we have a simple interface to help you out instead.

The offline middleware looks at your IRequest implementation. You can also implement the IRequestKey interface which is part of the Shiny.Mediator.Contracts library. This allows you to ‘build’ a key from possible arguments in your request object.

Example

public record MyRequest(string Arg1, int Arg2) : IRequest<IReadOnlyList<MyThingData>>, IRequestKey
{
    public string GetKey() => $"{this.Arg1}-{this.Arg2}";
}