Optionals in Go

This is a no nonsense zero dependency generic Optional<T> implementation for Go.

Installation

go get github.com/moveaxlab/go-optional

Usage

Return optionals from your repositories:

package repository

import (
  "context"

  "github.com/moveaxlab/go-optional"
)

type Repository interface {
  FindById(ctx context.Context, id string) optional.Optional[Entity]
}

type repository struct {}

func (r *repository) FindById(ctx context.Context, id string) optional.Optional[Entity] {
  var entity Entity
  var entityWasFound bool

  // retrieve the entity in some way

  if !entityWasFound {
    return optional.Empty[Entity]()
  }

  return optional.Of(&entity)
}

The use the optionals in your application logic:

package service

func (s *service) DoSomeStuff(ctx context.Context) {
  maybeEntity := s.repository.FindById(ctx, "1")

  if maybeEntity.IsPresent() {
    // we have the entity!
    entity := maybeEntity.Get()
  }
}

The Optional type offers these methods:

• IsPresent returns true if there is a value in the optional
• Get returns the value contained in the optional, and panics if it's empty
• OrElseGet accepts a function in input, and returns the value contained in the optional if present, or the result of the function otherwise
• OrElsePanic returns the value contained in the optional if present, or panics with a custom error passed in input
• IfPresent runs the function passed as argument if the value is present, passing it the value contained in the optional
• IfPresentOrElse behaves like IfPresent for the first argument, but calls the function passed as second argument if the optional is empty