struct Union(*T)
inherits Value
¶
A union type represents the possibility of a variable or an expression having more than one possible type at compile time.
When invoking a method on a union type, the language checks that the
method exists and can be resolved (typed) for each type in the union.
For this reason, adding instance methods to Union makes no sense and
has no effect. However, adding class method to Union is possible
and can be useful. One example is parsing JSON into one of many
possible types.
Union is special in that it is a generic type but instantiating it might not return a union type:
Union(Int32 | String) # => (Int32 | String)
Union(Int32) # => Int32
Union(Int32, Int32, Int32) # => Int32
Class methods¶
.nilable?
¶
Returns true if this union includes the Nil type.
(Int32 | String).nilable? # => false
(Int32 | Nil).nilable? # => true