This snippet demonstrates how to add a map field to a type.
We can use expression reification to turn basic types into appropriate expressions. Maps, however, are a complex type. As such they need to be treated a little differently.
A map is a container of key-value pairs that can be observed as an array of key => value expressions. For example: var m = [ 1 => "ONE", 2 => "TWO"]. With that in mind, building a map field is no different than creating an array of the correct expressions.
Note the use of macro to create the key => value expression. Also note the use of expression reification: $v{} to generate expressions from specified values, and $a{} to create the expression array.
Build macro
import haxe.macro.Context; import haxe.macro.Expr; class MapBuilder { public static macro function build(names : Array<String>) : Array<Field> { // The context is the class this build macro is called on var fields = Context.getBuildFields(); // A map is an array of `key => value` expressions var map : Array<Expr> = []; // We add a `key => value` expression for every name for (name in names) { // Expression reification generates expression from argument map.push(macro $v{name} => $v{haxe.crypto.Sha256.encode(name)}); } // We push the map into the context build fields fields.push({ // The line position that will be referenced on error pos: Context.currentPos(), // Field name name: "namesHashed", // Attached metadata (we are not adding any) meta: null, // Field type is Map<String, String>, `map` is the map kind: FieldType.FVar(macro : Map<String, String>, macro $a{map}), // Documentation (we are not adding any) doc: null, // Field visibility access: [Access.APublic, Access.AStatic] }); // Return the context build fields to build the type return fields; } }
Usage
@:build(MapBuilder.build(["Aaron", "Bobbi", "Carol", "Dennis", "Eric", "Frank"])) class Main { static function main() { trace(namesHashed.get("Bobbi")); } }
Learn about macros here: https://haxe.org/manual/macro.html
