Dart Map with String key, compare with ignore case

Question

Does the Map class in Dart have a way to ignore case if the key is a string?

Eg.

var map = new Map<String, int>(/*MyComparerThatIgnoresCase*/);
map["MyKey"] = 42;
var shouldBe42 = map["mykey"];

In C# the Dictionary constructor takes a comparer like the comment above. What is the canonical way to do this in Dart?

Answer 1

The way to create a HashMap with a custom equals function (and corresponding custom hashCode function) is to use the optional parameters on the HashMap constructor:

new HashMap<String,Whatever>(equals: (a, b) => a.toUpperCase() == b.toUpperCase(),
                             hashCode: (a) => a.toUpperCase().hashCode);

I really, really recommend finding a way to not do the toUpperCase on every operation!

Answer 2

You can also do this using package:collection's CanonicalizedMap class. This class is explicitly designed to support maps with "canonical" versions of keys, and is slightly more efficient than passing a custom equality and hash code method to a normal Map.