Gopt

A very light Optional implementation in Golang

Installation

To install Gopt, use go get:

go get github.com/go-andiamo/gopt

To update Gopt to the latest version, run:

go get -u github.com/go-andiamo/gopt

Examples

package main

import (
    . "github.com/go-andiamo/gopt"
)

func main() {
    optFlt := Of[float64](1.23)
    println(optFlt.IsPresent())
    println(optFlt.OrElse(-1))

    opt2 := Empty[float64]()
    println(opt2.IsPresent())
    println(opt2.OrElse(-1))

    opt2.OrElseSet(10)
    println(opt2.IsPresent())
    println(opt2.OrElse(-1))
}

Methods

Method and description	Returns
Get() returns the value and an error if the value is not present	(T, error)
AsEmpty() returns a new empty optional of the same type	Optional[T]
IsPresent() returns true if the value is present, otherwise false	bool
IfPresent(f func(v T)) if the value is present, calls the supplied function with the value, otherwise does nothing returns the original optional	Optional[T]
IfPresentOtherwise(f func(v T), other func()) if the value is present, calls the supplied function with the value, otherwise calls the other function returns the original optional	Optional[T]
OrElse(other T) returns the value if present, otherwise returns other	T
OrElseGet(f func() T) returns the value if present, otherwise returns the result of calling the supplied function	T
OrElseSet(v T) if the value is not present it is set to the supplied value	Optional[T]
OrElseError(err error) returns the supplied error if the value is not present, otherwise returns nil	error
OrElsePanic(v any) if the value is not present, panics with the supplied value, otherwise does nothing	nothing
DoWith(f func(v T)) if the value is present, calls the supplied function with the value returns the original optional	Optional[T]
Filter(f func(v T) bool) if the value is present and calling the supplied filter function returns true, returns a new optional describing the value Otherwise returns an empty optional	Optional[T]
Map(f func(v T) any) if the value is present and the result of calling the supplied mapping function returns non-nil, returns an optional describing that returned value Otherwise returns an empty optional	Optional[any]
MarshalJSON() implements JSON marshal if the value is present, returns the marshalled data for the value Otherwise, returns the marshalled data for null	([]byte, error)
UnmarshalJSON(data []byte) implements JSON unmarshal if the supplied data is null representation, sets the present to false Otherwise, unmarshal the data as the value and sets the optional to present (unless the result of unmarshalling the value returns an error - in which case the present is set to false)	error
Scan(value interface{}) implements sql.Scan	error

Constructors

Constructor function and description
Of[T any](value T) Optional[T] Creates a new optional with the supplied value
OfNillable[T any](value T) Optional[T] Creates a new optional with the supplied value If the supplied value is nil, an empty (not present) optional is returned
OfNillableString(value string) Optional[string] Creates a new string optional with the supplied value If the supplied value is an empty string, an empty (not-present) optional is returned
Empty[T any]() Optional[T] Creates a new empty (not-present) optional of the specified type