Effect.either

成功・失敗どちらも扱う

どちらのタスクが成功/失敗しても結果を処理したい場合に使う

code:ts

const program = Effect.race(

Effect.either(task1),

Effect.either(task2)

)

Effect.runPromise(program).then(console.log)

code:result

{

"_id": "Either",

"_tag": "Left",

"left": "task1"

}

error型のあるやつをEffect.eitherで囲うとEither (effect)に変換してくれる

code:ts

const recovered = Effect.gen(function* () {

// program :: Effect<string, HttpError | ValidationError, never>

// failureOrSuccess :: Either<string, HttpError | ValidationError>

const failureOrSuccess = yield* Effect.either(program)

if (Either.isLeft(failureOrSuccess)) {

// Failure case: you can extract the error from the left property

const error = failureOrSuccess.left

return Recovering from ${error._tag}

} else {

// Success case: you can extract the value from the right property

return failureOrSuccess.right

}

})