flutter - The method 'where' was called on null. Receiver: null Tried calling: where(Closure: (UserModel) => bool)

Question

I am having this error and i dont know how to resolved it pls help me out:

    The method 'where' was called on null.
Receiver: null
Tried calling: where(Closure: (UserModel) => bool)

This is where the error is coming from:

The List is of type the UserModel class which is writen below

List<UserModel> userList;

final List<UserModel> suggestionList = query.isEmpty
    ?[]
    : userList.where((UserModel user) {
      String _getUsername = user.username.toLowerCase();
      String _query = query.toLowerCase();
      String _getName = user.name.toLowerCase();
      bool matchesUsername = _getUsername.contains(_query);
      bool matchesName = _getName.contains(_query);

      return (matchesUsername || matchesName);
}).toList();

This is the class which the userList is calling from: This is the Model class that is begin called.

    class UserModel {
  String uid;
  String name;
  String email;
  String username;
  String status;
  int state;
  String profilePhoto;

  UserModel({
    this.uid,
    this.name,
    this.email,
    this.username,
    this.status,
    this.state,
    this.profilePhoto,
  });

  Map toMap(UserModel user) {
    var data = Map<String, dynamic>();
    data['uid'] = user.uid;
    data['name'] = user.name;
    data['email'] = user.email;
    data['username'] = user.username;
    data["status"] = user.status;
    data["state"] = user.state;
    data["profile_photo"] = user.profilePhoto;
    return data;
  }

  UserModel.fromMap(Map<String, dynamic> mapData) {
    this.uid = mapData['uid'];
    this.name = mapData['name'];
    this.email = mapData['email'];
    this.username = mapData['username'];
    this.status = mapData['status'];
    this.state = mapData['state'];
    this.profilePhoto = mapData['profile_photo'];
  }
}

question from:https://stackoverflow.com/questions/65843105/the-method-where-was-called-on-null-receiver-null-tried-calling-whereclosu

Answer 1

The "userList" variable is not initialized. The easiest fix you can do is to initialize it with an empty list when you declare it.

List<UserModel> userList = <UserModel>[];