Extension Iterable

main.dart

void main() {
  final list = ['a', 'b', 'c'];
  list.mapIndex((i, index) {
    print("item $i inddex $index ");
  }).toList();

  print("===============");
  
  list.forEachIndex((i, index) {
    print("item $i inddex $index ");
  });
    print(list.getOrElse(7,()=>"7"));

}

extension ExtensionIterable<E> on Iterable<E> {
  Iterable<T> mapIndex<T>(T f(E e, int i)) {
    var i = 0;
    return this.map((e) => f(e, i++));
  }

  void forEachIndex(void f(E e, int i)) {
    var i = 0;
    this.forEach((e) => f(e, i++));
  }

  E getOrNull(int index) {
    try {
      return this.elementAt(index);
    } catch (e) {
      return null;
    }
  }
  E getOrElse(int index, E f()) {
    try {
      return this.elementAt(index);
    } catch (e) {
      return f();
    }
  }
}