github.com/typomaker/option

Optional type for the Golang. A generic value wrapper that adds two additional value representations:

• Zero - Same as undefined. Basic value state, persists until None or Some value is assigned.
• None - Same as null. A logically explicit absence of a value.
• Some - Usual value representation.

Usage

import "github.com/typomaker/option"

Value initialization and checks.

import "github.com/typomaker/option"
var value option.Option[string]
if value.IsZero() { // if value is undefined.
    value = option.Some("foo") // then define it using Some[string](...).
}
if value.IsSome() { // if value is defined and not null
    value = option.None[string]() // then set it null using None[string]() 
}
if value.IsNone() { // if value is defined and null
    value = option.Option[string]{} // then undefine it with the zero Option struct.
}

Value getting.

var value option.Option[string]

value.Get() // returns value if defined not null, otherwise panics.
value.GetOr("fallback") // returns value if defined not null, otherwise passed value.
value.GetOrZero() // always returns value, if undefined or null then zero value.
value.GetOrFunc(func() string {return "fallback"}) // returns a value if defined not null. otherwise, returns the result of the passed function.

Nilable value.

var value *string 
var optional = option.Nilable(value) // If value is not nil, then returns Some[string](*value), otherwise None[string]().
value = optional.GetNilable() // returns &value is some, otherwise returns nil.

Convert value to optional.

Maybe function returns Some[T](...) for non zero and not nil value, otherwise returns None[T]()

fmt.Printf("%#v\n", Maybe(0))
fmt.Printf("%#v\n", Maybe(1))
fmt.Printf("%#v\n", Maybe((*string)(nil)))
fmt.Printf("%#v\n", Maybe("123123"))
// Output:
// None[int]()
// Some[int](1)
// None[*string]()
// Some[string]("123123")

OneOf helper

Returns first some option from passed. If passed doesn't contain some value, then returns None[T]().

var value1 = option.None[int]()
var value2 = option.Some[int](1)
var value3 = option.Some[int](2)

fmt.Printf("%#v", option.OneOf(value1, value2, value3))

// Output:
// Some[int](1)

GetOf helper

Returns value of first some option from passed.

var value1 = option.None[int]()
var value2 = option.Some[int](1)
var value3 = option.Some[int](2)

fmt.Printf("%#v", option.GetOf(value1, value2, value3))

// Output:
// 1

PickOf helper

Returns all some option from passed.

var value1 = option.None[int]()
var value2 = option.Some[int](1)
var value3 = option.Some[int](2)

fmt.Printf("%#v", option.PickOf(value1, value2, value3))

// Output:
// []int{1, 2}