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stringdartiterationiterable
David K.
David K.

Reputation: 6361

Dart String Iterable interface

Why doesn't Dart String class implement the iterable interface? It seems like there is an obvious notion of iteration for strings, i.e. just return each character in turn.

Upvotes: 4

Views: 2854

Answers (3)

Erisan Olasheni
Erisan Olasheni

Reputation: 2905

You can easily convert Dart to List by using .split('') and you can use it as Iterable, because List is a subclass.

String s = 'foo';
for(String d in s.split('')) {
 print(d);
}

Upvotes: 2

lrn
lrn

Reputation: 71643

To answer the "Why":

The Iterable interface is a fairly heavy-weight interface (many members) that is intended for collections of elements.

While a String can be seen as a List of characters (but Dart doesn't have a type for characters, so it would really be "List of single-character Strings"), that is not its main usage, and also being an Iterable would clutter the actual String methods.

A better solution would be to have a List view of a String. That is fairly easily doable:

class StringListView extends ListBase<String> {
  final String _string;
  StringListView(this._string);

  @override
  String operator [](int index) => _string[index];

  @override
  int get length => _string.length;

  @override
  set length(int newLength) {
    throw UnsupportedError("Unmodifiable");
  }

  @override
  void operator []=(int index, String v) {
    throw UnsupportedError("Unmodifiable");
  }
}

Would be even easier if the libraries exposed the UnmodifiableListBase used to make UnmodifiableListView.

Upvotes: 5

G&#252;nter Z&#246;chbauer
G&#252;nter Z&#246;chbauer

Reputation: 657248

Maybe not that terse as you would like 

String s = 'foo';
s.codeUnits.forEach((f) => print(new String.fromCharCode(f)));
s.runes.forEach((f) => print(new String.fromCharCode(f)));

Upvotes: 4

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