如果你在List.generate中打开回调函数，你可以执行多行操作（通过删除箭头函数声明），你可以执行任意多个if语句。例如下面的示例，扩展了num类以包含2种类型的in between函数，从而使if语句更简洁

final List<Map<dynamic, dynamic>> flashcards = List.generate(10, (index) {
    if (index.isBetweenInclusive(0, 3)) {
        return {
            "isSelected": false,
            "id": index,
            "front": "front $index",
            "back": "back $index",
            "reviewDate": DateTime.now(),
            "answerStreak": 0,
        };
    } else if (index.isBetweenInclusive(4, 7)) {
        return {
            "isSelected": false,
            "id": index,
            "front": "front $index",
            "back": "back $index",
            "reviewDate": DateTime.now(),
            "answerStreak": 0,
        };
    } else {
        return {
            "isSelected": false,
            "id": index,
            "front": "front $index",
            "back": "back $index",
            "reviewDate": DateTime.now(),
            "answerStreak": 0,
        };
    }
});

extension Range on num {
  bool isBetween(num from, num to) {
    return from < this && this < to;
  }
}

extension Range on num {
  bool isBetweenInclusive(num from, num to) {
    return from <= this && this <= to;
  }
}

试试这个

const abc = ["A", "B", "C"];
void main() {
  final List<Map<dynamic, dynamic>> flashcards = List.generate(
      10,
      (index) => {
            "isSelected": false,
            "id": index,
            "front": "front $index",
            "back": "back $index",
            "reviewDate": DateTime.now(),
            "answerStreak": 0,
            "Type": abc[index ~/ 4]
          });
}