How do I split or chunk a list into equal parts, with Dart?

Question

Assume I have a list like:

var letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'];

I would like a list of lists of 2 elements each:

var chunks = [['a', 'b'], ['c', 'd'], ['e', 'f'], ['g', 'h']];

What's a good way to do this with Dart?

Answer 1

Here is another way:

  var chunks = [];
  int chunkSize = 2;
  for (var i = 0; i < letters.length; i += chunkSize) {
    chunks.add(letters.sublist(i, i+chunkSize > letters.length ? letters.length : i + chunkSize)); 
  }
  return chunks;

Run it on dartpad

Answer 2

Quiver (version >= 0.18) supplies partition() as part of its iterables library (import 'package:quiver/iterables.dart'). The implementation returns lazily-computed Iterable, making it pretty efficient. Use as:

var letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'];
var pairs = partition(letters, 2);

The returned pairs will be an Iterable<List> that looks like:

[['a', 'b'], ['c', 'd'], ['e', 'f'], ['g', 'h']]

Answer 3

A slight improvement on Seth's answer to make it work with any list or chunk size:

var len = letters.length;
var size = 2;
var chunks = [];

for(var i = 0; i< len; i+= size)
{    
    var end = (i+size<len)?i+size:len;
    chunks.add(letters.sublist(i,end));
}