Cancelling Requests

In some scenarios, you may want to cancel a long-running HTTP request if it’s no longer needed, such as when a user navigates away from a page or dismisses a loading UI. Uxios provides built-in support for cancelling requests, simplifying how you manage these situations.

This guide explains how to cancel requests in Uxios using the Abort method or through coroutine-based automatic cancellation. By attaching promises to Uxios’s AbortController, you can efficiently manage the lifecycle of HTTP requests in your Unity projects.

Cancellation Mechanism

It’s the HTTP request that gets cancelled, not the promise itself. If the HTTP request has already completed, cancellation has no effect on the handling of the response.

Example Use Cases

• Cancelling a data fetch if the user leaves a page or closes a dialog.
• Stopping requests that are no longer relevant, saving resources and improving performance.
• Automatically aborting requests associated with coroutines when they stop.

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Step 1: Start the Request

Initiate the request using Uxios as you normally would. A promise is returned, which you can use to track and handle the request.

var url = new Uri("https://httpbin.org/delay/10");
var promise = uxios.Get<string>(url);

In this example:

• The URL https://httpbin.org/delay/10 simulates a delay, allowing you to test the cancellation mechanism.

Step 2: Cancel the Request

To cancel the request, simply call the Abort method on the Uxios instance and pass in the promise. For example, if a user action triggers cancellation:

uxios.Abort(promise);

This aborts the associated HTTP request as soon as possible. If the request was already completed, this action will have no effect on the response handling.

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Using Promises in Coroutines

When using promises in a coroutine, you can utilize Uxios's built-in coroutine helpers, such as WaitForRequest or AsCoroutine. These methods ensure that:

1. The promise remains alive as long as the coroutine is running.
2. If the coroutine unexpectedly stops, Uxios automatically calls Abort on the associated promise.

Example:

private IEnumerator FetchData()
{
    var url = new Uri("https://httpbin.org/delay/10");
    var promise = uxios.Get<string>(url);

    yield return promise.WaitForRequest();

    Debug.Log("Request completed: " + promise.CurState);
}

private StoppingACoroutine()
{
    var coroutine = StartCoroutine(FetchData);

    // This will automatically abort the request in the
    // next frame
    StopCoroutine(coroutine);
}        

If the coroutine is stopped, the associated promise will be aborted automatically. There’s no need to manually manage cancellation in this scenario.

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Summary

In this guide, you learned how to cancel requests in Uxios using the Abort method and the automatic cancellation mechanism for coroutines. Key takeaways:

• Step 1: Start a request as usual.
• Step 2: Cancel a request manually by calling Abort on the promise.
• Coroutine Handling: Promises used in coroutines are automatically aborted when the coroutine stops.