Optionals

This Package provides the Optional{T} type, this type is a simple wrapper around Union{T, Missing} at least semantically.

Why should I use this package?

In Julia 0.7 and above the Union{T, Missing} type makes it quite convenient to use fields with optional values. The Missings package tries to backport this feature to 0.6, unfortunately v0.6 is not very efficient in using Union fields. In the interim Optional provides a somewhat more efficient way for packages which need to support both v0.6 and newer. After dropping support for v0.6 and older, Optional{T} can simply be replaced with Union{T, Missing} (hopefully) without further changes.

How to use

using Optionals

struct Foo
   x::Optional{Int}
end

Construction without a value: Foo(missing)

Construction with a value: Foo(42)

Test if field x has a value: ismissing(foo.x)

Get value or replace missing with default: coalesce(foo.x, 42)

Convert an Optional{T} to a Union{T, Missing}: coalesce(foo.x)