How can I use coalescing operator in Haxe? - operators

Question

As I mentioned in the question,
How can I use coalescing operator in Haxe?

Answer 1

Haxe does not have a null coalescing operator like C#'s ??.
That being said, it's possible to achieve something similar with macros. It looks like somebody has already written a library that does exactly this a few years ago. Here's an example from its readme:
var s = Sys.args()[0];
var path = s || '/default/path/to/../';
It uses the existing || operator because macros can not introduce entirely new syntax.
However, personally I would probably prefer a static extension like this:
class StaticExtensions {
public static function or<T>(value:T, defaultValue:T):T {
return value == null ? defaultValue : value;
}
}
using StaticExtensions;
class Main {
static public function main() {
var foo:String = null;
trace(foo.or("bar")); // bar
}
}
Instead of making your own, you could also consider using the safety library, which has a number of additional static extensions for Null<T> and features for dealing with null in general.

Answer 2

Use this addon:
https://github.com/skial/nco
Then, type
var value = a || 'backup value';
instead of
var value = (a == null) ? 'backup value' : a;

Answer 3

You can also utilize abstracts instead of macros for this purpose
class Test {
static function main() {
trace("Haxe is great!");
var s:Ory<String> = "hi!";
trace(s || "I don't get picked");
s = null;
trace(s || "I get picked");
trace(s + "!");
}
}
#:forward abstract Ory<T>(T) from T to T {
#:op(a||b) public inline function or(b:T):Ory<T> {
return this != null ? this : b;
}
}