10.2.5 Map

A Map is a container composed of key, value pairs. A Map is also commonly referred to as an associative array, dictionary, or symbol table. The following code gives a short example of working with maps:

class Main {
  static public function main() {
    // Maps are initialized like arrays, but
    // use the map literal syntax with the
    // '=>' operator. Maps can have their
    // key value types defined explicity
    var map1:Map<Int, String> =
      [1 => "one", 2=>"two"];

    // Or they can infer their key value types
    var map2 = [
      "one"=>1,
      "two"=>2,
      "three"=>3
    ];
    $type(map2); // Map<String, Int>

    // Keys must be unique
    // Error: Duplicate Key
    //var map3 = [1=>"dog", 1=>"cat"];

    // Maps values can be accessed using array
    // accessors "[]"
    var map4 = ["M"=>"Monday", "T"=>"Tuesday"];
    trace(map4["M"]); //Monday

    // Maps iterate over their values by
    // default
    var valueSum;
    for (value in map4) {
      trace(value); // Monday \n Tuesday
    }

    // Can iterate over keys by using the
    // keys() method
    for (key in map4.keys()) {
      trace(key); // M \n T
    }

    // Like arrays, a new Map can be made using
    // comprehension
    var map5 = [
      for (key in map4.keys())
        key => "FRIDAY!!"
    ];
    // {M => FRIDAY!!, T => FRIDAY!!}
    trace(map5);
  }
}

Under the hood, a Map is an abstract type. At compile time, it gets converted to one of several specialized types depending on the key type:

• String: haxe.ds.StringMap
• Int: haxe.ds.IntMap
• EnumValue: haxe.ds.EnumValueMap
• {}: haxe.ds.ObjectMap

The Map type does not exist at runtime and has been replaced with one of the above objects.

Map defines array access using its key type.

See the Map API for details of its methods.