Reference · Core Type

ReaderIOResult

Combine dependency injection (Reader) + lazy effects (IO) + Go error handling (Result). ReaderIOResult[C, A] is ReaderIOEither specialized for error.

Packagegithub.com/IBM/fp-go/v2/readerioresult

TypeMonad (func(C) IO[Result[A]])

01

Overview

type_definition.go

package readerioresult

// ReaderIOResult is ReaderIOEither specialized for error
type ReaderIOResult[C, A any] = ReaderIOEither[C, error, A]
// Which expands to: func(C) func() Either[error, A]

02

Core API

Constructors

Function	Signature	Description
Ok	func Ok[C, A any](value A) ReaderIOResult[C, A]	Create successful value
Error	func Error[C, A any](err error) ReaderIOResult[C, A]	Create error value
Of	func Of[C, A any](value A) ReaderIOResult[C, A]	Alias for Ok
Ask	func Ask[C any]() ReaderIOResult[C, C]	Access context

Transformations

Function	Signature	Description
Map	func Map[C, A, B any](f func(A) B) func(ReaderIOResult[C, A]) ReaderIOResult[C, B]	Transform success value
Chain	func Chain[C, A, B any](f func(A) ReaderIOResult[C, B]) func(ReaderIOResult[C, A]) ReaderIOResult[C, B]	Sequence operations

03

Usage Examples

Basic Usage

basic.go

package main

import (
  RIOR "github.com/IBM/fp-go/v2/readerioresult"
)

type Dependencies struct {
  DB *sql.DB
}

func fetchUser(id string) RIOR.ReaderIOResult[Dependencies, User] {
  return RIOR.Ask[Dependencies, *sql.DB](func(deps Dependencies) *sql.DB {
      return deps.DB
  }).Chain(func(db *sql.DB) RIOR.ReaderIOResult[Dependencies, User] {
      return RIOR.TryCatchError(func() (User, error) {
          return db.QueryUser(id)
      })
  })
}