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Uniontypes

For those libraries that return one thing or another. Similar to Union types in Typescript.

Installation

haxelib install uniontypes then put -lib uniontypes in your .hxml.

Usage

final x : Union<Int, String> = "A string";

switch x.type() {
    case Int(i): trace('It was an Int: $i');
    case String(s): trace('It was a String: ${s.toUpperCase()}');
    case Null: trace('It was null');
}

The Union type is for two types, but the library also includes Union3, Union4, Union5 and Union6 for more extreme cases.

To trust, or not to trust

Depending on how much you trust the data in the union, you can specify different types of unions:

  • Union.TrustedUnion assumes a value will never be null, meaning a Null enum constructor will not exist.
  • Union.UntrustedUnion includes both a Null and an Unknown(u : Dynamic) enum constructor, to guarantee coverage of all cases, however improbable.

Special case: Anonymous structures

Since an anonymous structure isn't a defined type, it cannot be detected in the same way as a well-defined type like a Class, Enum or basic types like Int, String, etc. Reflection is instead used to compare the (non-optional) fields of anonymous structures to see if they unify, which on dynamic targets shouldn't make much of a difference in speed. The library is optimizing for this case however, placing all anonymous structures last, moving the more expensive operation to the else part of the condition.