yield 就是固定返回一个“数组”代码里yield 相当于数据的add
main() {
getEmoji(10).forEach(print);
}
Iterable<String> getEmoji(int count) sync* {
Runes first = Runes('\u{1f47f}');
for (int i = 0; i < count; i++) {
yield String.fromCharCodes(first.map((e) => e + i));
}
}