opt

README

go-opt

go-opt is an implementation of optional values in go.
Optional values can have a number of use cases such as:

• Providing optional parameters to functions
• Representing a look-up value that could be present or absent in particular context.

An optional value implements the following interface

package opt

type Option[T any] interface {

	// Get returns value of type T if present or panic if absent
	Get() T

	// GetOrElse returns value of type T if present else return the value passed
	// as a parameter.
	GetOrElse(T) T

	// GetOrZero returns value of type T if present else returns the zero value of T.
	GetOrZero() T

	// Empty returns true if value is absent else returns false.
	Empty() bool
}

This module provides two implementations of the Option[T] interface

• Some[T]
• None[T]

Installation

go get github.com/iUwej/go-opt

Usage

1. To create an option with a value present, use the Some function.

package main

import "github.com/iUwej/go-opt"

intOpt := opt.Some(5) // creates an int option
strOpt := opt.Some("some string")
custOpt := opt.Some(CustomType())

1. To create an option with a value absent, use the None function.

package main

import "github.com/iUwej/go-opt"

intOpt := opt.None[int]()
strOpt := opt.None[string]()
custOpt := opt.None[CustomType]()

Example

package main

import "github.com/iUwej/go-opt"



type User struct {
	Id     int64
	Name   string
	Emails []string
}

func FindUser(id string)opt.Option[User]  {
	user := User{
		Id : id,
		Name:   "admin",
		Emails: []string{"admin1@admin", "admin2@admin"},
	}
	if true{
		return opt.Some(user)
    } else{
		return opt.None[User]()
    }
	
}

func main() {
    userOpt := FindUser("some_id")
	// check if user present
	if userOpt.Empty(){
		//do something if userOpt is empty
    }
	// get the user if present or provide a default
	user := userOpt.GetOrElse(User{id:"back_up",Name: "Some Name"})
	
	//map the optional user into an optional name
	nameOpt := opt.Map(func(t User) string {
        return t.Name
	},userOpt)
}

Documentation

Overview

Package opt provides the specification and implementation of golang's optional values.

Index

• type Option
  • func Map[T, K any](mapper func(t T) K, opt Option[T]) Option[K]
  • func None[T any]() Option[T]
  • func Some[T any](val T) Option[T]

Types

type Option

type Option[T any] interface {

	// Get returns value of type T if present or panic if absent
	Get() T

	// GetOrElse returns value of type T if present else return the value passed
	// as a parameter.
	GetOrElse(T) T

	// GetOrZero returns value of type T if present else returns the zero value of T.
	GetOrZero() T

	// Empty returns true if value is absent else returns false.
	Empty() bool
}

Option defines the specification for a golang optional value.

func Map

func Map[T, K any](mapper func(t T) K, opt Option[T]) Option[K]

Map convert an Option of type T to an Option of type K.

func None

func None[T any]() Option[T]

None returns the absent value for some type T.

func Some

func Some[T any](val T) Option[T]

Some returns an Option with value of type T present.