Update dart snippet

content/snippets/dart-how-to-get-the-index-on-array-loop-map.md

@@ -20,21 +20,35 @@ Unlike JavaScript, one cannot simply access the index of a list during a `List.m
 
 {{< file "dart" "main.dart" >}}
 ```dart
-List myList = ['a', 'b', 'c'];
+final myList = ['a', 'b', 'c'];
 
 myList.map( (val, index) {
     // This does not work!
     // Which index am I on?
-})
+});
 ```
 
 ## Solutions
 
 There are several ways to access the index when looping over a List. 
 
+### Use `indexed`
+
+Every `Iterable` has an [`indexed`](https://api.dart.dev/dart-collection/IterableExtensions/indexed.html) extension available, you can call it to have a new `Iterable` of `(int, E)`.
+
+{{< file "dart" "main.dart" >}}
+```dart
+myList.indexed.map((entry) {
+    int idx = entry.$1;
+    String val = entry.$2;
+
+    return something;
+});
+```
+
 ### Use Map Entries
 
-Convert the `List` to a `Map`, then map the [entries](https://api.dartlang.org/stable/2.0.0/dart-core/Map/entries.html) containing the key/value pairs. Each key in the map is the index of the original list. 
+Convert the `List` to a `Map`, then map the [entries](https://api.dart.dev/dart-core/Map/entries.html) containing the key/value pairs. Each key in the map is the index of the original list. 
 
 {{< file "dart" "main.dart" >}}
 ```dart
@@ -43,7 +57,7 @@ myList.asMap().entries.map((entry) {
     String val = entry.value;
 
     return something;
-}
+});
 ```
 
 
@@ -52,28 +66,28 @@ myList.asMap().entries.map((entry) {
 If you are looping over many lists that have a fixed length, it may be more efficient to generate a single list once. For example, the we create a ranged list that is the same length as the original, i.e. `[0, 1, 2, ..., n]`
 
 ```dart
-final List fixedList = Iterable<int>.generate(myList.length).toList();
+final fixedList = List.generate(myList.length, (i) => i);
 
 
 fixedList.map((idx) {
     String val = myList[idx];
 
     return something;
-}
+});
 ```
 
 
 ### Grab the Index of Unique Values
 
-You can access the index of a specific value by searching for it with [List.indexOf](https://api.dartlang.org/stable/2.6.1/dart-core/List/indexOf.html), which returns the index of the first match. This approach is most predictable when all values are unique. A [Set](https://api.dartlang.org/stable/2.6.1/dart-core/Set-class.html) can ensure uniqueness throughout the list. 
+You can access the index of a specific value by searching for it with [List.indexOf](https://api.dart.dev/dart-core/List/indexOf.html), which returns the index of the first match. This approach is most predictable when all values are unique. A [Set](https://api.dart.dev/dart-core/Set-class.html) can ensure uniqueness throughout the list. 
 
 ```dart
-final List uniqueList = Set.from(myList).toList();
+final uniqueList = Set.of(myList).toList();
 
 
 uniqueList.map((val) {
     String idx = uniqueList.indexOf(val);
 
     return something;
-}
+});
 ```