IO<Operation>

The IO container is for isolating side effects in your program. This container is lazy and will not be evaluated until the unwrap method is called.

IO constructor

You can create an IO by calling the of constructor

const fetch = IO.of(fetch('http://localhost:8080/api/users')) // IO(Promise<Users>)

const aNumber = IO.of(3) // IO(3)

Methods

The IO container exposes several methods for value manipulation

.map(fn)

IO<T>.map<R>(fn: (input: T) => R): IO<R>

const ioValue = IO.of(5);
const newValue = ioValue.map(x => x * 2); // IO(10)

const ioString = IO.of("hello");
const upperCaseValue = ioString.map(str => str.toUpperCase()); // IO("HELLO")

.flatMap(fn)

IO<T>.flatMap<R>(fn: (input: T) => IO<R>): IO<R>

Transforms the value inside the IO into another IO and flattens the result.

const ioValue = IO.of(5);
const newValue = ioValue.flatMap(x => IO.of(x * 2)); // IO(10)

const ioString = IO.of("hello");
const upperCaseValue = ioString.flatMap(str => IO.of(str.toUpperCase())); // IO("HELLO")

.unwrap()

IO<T>.unwrap(): T

Computes and returns the value inside the IO.

const ioValue = IO.of(5);
console.log(ioValue.unwrap()); // 5

const ioString = IO.of("hello");
console.log(ioString.unwrap()); // "hello"

.toMaybe()

IO<T>.toMaybe(): maybe<T>

Converts the IO to a maybe.

const ioValue = IO.of(5);
const maybeValue = ioValue.toMaybe(); // Some(5)

const ioNull = IO.of(null);
const maybeNull = ioNull.toMaybe(); // None