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.StringMapInt: haxe.ds.IntMapEnumValue: haxe.ds.EnumValueMap{}: haxe.ds.ObjectMapThe 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.