flutter - 从对象列表创建副本并更改新列表，而不更改原始的一个 flutter

Question

我有一个对象列表，我想获得该对象的副本并在不更改原始对象的情况下更改新对象。

List<Comment> manageComment(List<Comment> incomingComments) {
  List<Comment> finalArr = [];
    var comments = List.from(incomingComments);
  while (comments.isNotEmpty) {
    var comment = comments.removeAt(0);
    if (comment.parentId == null) {
      finalArr.add(comment);
    } else {
      for (var i = 0; i < finalArr.length; i++) {
        var el = finalArr[i];
        if (el.commentId == comment.parentId) {
          comment.replyTo = el.user;
          el.children.add(comment);
          break;
        } else {
          for (var j = 0; j < el.children.length; j++) {
            var childEl = el.children[j];
            if (childEl.commentId == comment.parentId) {
              comment.replyTo = childEl.user;
              el.children.add(comment);
              break;
            }
          }
        }
      }
    }
  }
    print(finalArr[0].children);
    return finalArr;
}

评论类:

class Comment {
  String commentId;
  User user;
  User replyTo;
  String text;
  num date;
  String parentId;
  List<Comment> children;

  Comment({
    this.commentId,
    this.user,
    this.replyTo,
    this.text,
    this.date,
    this.parentId,
    this.children,
  });

  Comment copyWith({
    String commentId,
    User user,
    User replyTo,
    String text,
    num date,
    String parentId,
    List<Comment> children,
  }) {
    return Comment(
      commentId: commentId ?? this.commentId,
      user: user ?? this.user,
      replyTo: replyTo ?? this.replyTo,
      text: text ?? this.text,
      date: date ?? this.date,
      parentId: parentId ?? this.parentId,
      children: children ?? this.children,
    );
  }

  Comment.fromJson(Map json)
      : commentId = json['commentId'],
        text = json['text'],
        parentId = json['parentId'],
        user = User.fromJson(json['user']),
        children = [],
        date = json['date'];
}

我尝试了这个，但它也改变了原始列表。

我怎样才能实现这一目标？

Answer 1

我找到了这个解决方案并且有效:

在评论类(class)中:

  Comment.clone(Comment source)
      : this.commentId = source.commentId,
        this.user = source.user,
        this.replyTo = source.replyTo,
        this.text = source.text,
        this.date = source.date,
        this.parentId = source.parentId,
        this.children = source.children.map((item) => Comment.clone(item)).toList();

并获取副本:

var comments = incomingComments.map((e) => Comment.clone(e)).toList();

reference link