Async Programming with Monads

Both Result<T> and Maybe<T> provide full async support for all major operations.

Async Map

Result

var result = await Result.Success("file.txt")
    .Map(async fileName => await File.ReadAllTextAsync(fileName));

Maybe

var maybe = await Maybe.Some("data")
    .Map(async data => await ProcessDataAsync(data));

Async Bind

Result

public async Task<Result<User>> GetUserAsync(int id) =>
    await ValidateId(id)
        .Bind(async validId => await database.GetUserAsync(validId));

Maybe

var result = await Maybe.Some(userId)
    .Bind(async id => await FindUserAsync(id));

Async Side Effects

Result

var result = await CreateUserAsync(email)
    .IfSuccess(async user => await SendWelcomeEmailAsync(user))
    .IfFailure(async error => await LogErrorAsync(error));

Maybe

await maybe
    .IfSome(async value => await ProcessValueAsync(value))
    .IfNone(async () => await HandleMissingValueAsync());

Async Match

var message = await result.Match(
    async user => await FormatUserDetailsAsync(user),
    async error => await FormatErrorMessageAsync(error)
);

Async Ensure

var validated = await result
    .Ensure(async user => await IsUserActiveAsync(user),
            new LogicError("User is not active"));

Task Extensions

All methods work seamlessly with Task<Result<T>> and Task<Maybe<T>>:

public async Task<Result<ProcessedData>> ProcessUserDataAsync(int userId)
{
    return await GetUserAsync(userId)          // Task<Result<User>>
        .Bind(async user => await GetUserDataAsync(user.Id))
        .Map(async data => await ProcessDataAsync(data))
        .IfSuccess(async result => await CacheResultAsync(result));
}

Safe Async Execution

// Catches exceptions as RuntimeError
var result = await Result.Execute(async () =>
    await RiskyAsyncOperation()
);

See Also

Result\ Monad Core Result monad operations and patterns

Maybe\ Monad Core Maybe monad operations and patterns