FluentUtils.Monad 2.0.0

FluentUtils.Monad

This library contains an implementation of the Result monad.

Basic Usage

var okResult = Result.Ok("bob");

// access value of result
okResult.Match(
    value => Console.WriteLine(value),       // "bob"
    err => Console.WriteLine(err.ToString()) // skipped
);

var errResult = Result.Error(new Error(new ErrorCode("1"), new ErrorMessage("No bob")));

errResult.Match(
    value => Console.WriteLine(value),       // skipped
    err => Console.WriteLine(err.ToString()) // "1: Not bob"
);

Async Usage

Order result = await CreateOrderAsync().MatchAsync(
    async (order, token) => await UpdateOrderAsync(order, token),
    async (err, token) => await ErrorOrderAsync(err, token),
    cancellationToken
);

Concepts

Creating Results

Result.Ok

Creates the OkResultType<T> from a value that you provide, or an Empty value if you do not provide one.

ResultType<string> result = Result.Ok("Hello World");
//^? OkResultType<string>

ResultType<Empty> result = Result.Ok();
//^? OkResultType<Empty>

Result.Error

Creates the ErrorResultType<T> from an error that you provide.

ResultType<string> result = Result.Error<string>(new Error("Code", "Message"));
//^? ErrorResultType<string>

ResultType<Empty> result = Result.Error(new Error("Code", "Message"));
//^? ErrorResultType<Empty>

Bind

Binds a factory method into a result type by executing it inside a try/catch block and converting the result of the factory into an OkResultType<T> if it is successful, or an ErrorResultType<T> if it throws an exception.

ResultType<string> okResult = Result.Bind(() => "hello world");
//                 ^? OkResultType<string>

ResultType<string> errorResult = Result.Bind(() => throw Exception());
//                 ^? ErrorResultType<string>

Accessing the Value inside a Result

Match

Checks the state of a ResultType<T>, executing an okHandler if it is an OkResultType<T> or an errorHandler if it is an ErrorResultType<T>.

See Basic Usage for an example

Unwrap

Extracts the value from a ResultType<T> without checking if it is an OkResultType<T> or an ErrorResultType<T>.

string value = Result.Ok("Hello World").Unwrap();
//     ^? "Hello World"

Result.Error(new Error("Code", "Message")).Unwrap();
//                                         ^? throws UnwrapPanicException

Transforming the Value inside a Result

Pipe

Transforms the value of a ResultType<T> using the provided function if it is an OkResultType<T>, otherwise propagates the error of the ErrorResultType<T>.

bool stringIsGreaterThanFive = Result.Bind(() => "hello world")
                                  .Pipe(value => value.Length)
                                  .Pipe(length => length >= 5)
                                  .Unwrap();

Executing Side Effects on the Value of a Result

Tap

Access the value of a result to execute a side effect. The result will be converted into an ErrorResultType<T> if the side effect fails to execute due to an exception.

Result.Ok("Hello World")
    .Tap(value => Console.WriteLine(value));

Ensure

Ensures the value of a result passes the provided predicate. The result will be converted into a ErrorResultType<T> if the predicate does not return true

string result = Result.Ok("Hello World")
    .Ensure(value => value.Length >= 1)
    .Pipe(value => value.ToUpperCase())
    .Unwrap();  // -> "HELLO WORLD"