使用 ! 时用于空值错误的空值检查运算符颤振中的操作员

Answer 1

试试下面的代码：

class Client {
  List<Clients>? clients;

  Client({this.clients});

  Client.fromJson(Map<String, dynamic> json) {
    if (json['clients'] != null) {
      clients = <Clients>[];
      json['clients'].forEach((v) {
        clients?.add(new Clients.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    if (this.clients != null) {
      data['clients'] = this.clients?.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class Clients {
  int? id;
  String? name;
  String? address;
  String? tinNo;
  String? status;
  String? createdAt;
  String? updatedAt;
  List<Phones>? phones;

  Clients(
      {this.id,
      this.name,
      this.address,
      this.tinNo,
      this.status,
      this.createdAt,
      this.updatedAt,
      this.phones});

  Clients.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    name = json['name'];
    address = json['address'];
    tinNo = json['tin_no'];
    status = json['status'];
    createdAt = json['created_at'];
    updatedAt = json['updated_at'];
    if (json['phones'] != null) {
      phones = <Phones>[];
      json['phones'].forEach((v) {
        phones?.add(new Phones.fromJson(v));
      });
    }
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['name'] = this.name;
    data['address'] = this.address;
    data['tin_no'] = this.tinNo;
    data['status'] = this.status;
    data['created_at'] = this.createdAt;
    data['updated_at'] = this.updatedAt;
    if (this.phones != null) {
      data['phones'] = this.phones?.map((v) => v.toJson()).toList();
    }
    return data;
  }
}

class Phones {
  int? id;
  String? clientId;
  Null? supplierId;
  Null? companyId;
  String? phoneNumber;
  String? email;
  String? model;
  String? category;
  String? createdAt;
  String? updatedAt;

  Phones(
      {this.id,
      this.clientId,
      this.supplierId,
      this.companyId,
      this.phoneNumber,
      this.email,
      this.model,
      this.category,
      this.createdAt,
      this.updatedAt});

  Phones.fromJson(Map<String, dynamic> json) {
    id = json['id'];
    clientId = json['client_id'];
    supplierId = json['supplier_id'];
    companyId = json['company_id'];
    phoneNumber = json['phone_number'];
    email = json['email'];
    model = json['model'];
    category = json['category'];
    createdAt = json['created_at'];
    updatedAt = json['updated_at'];
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['client_id'] = this.clientId;
    data['supplier_id'] = this.supplierId;
    data['company_id'] = this.companyId;
    data['phone_number'] = this.phoneNumber;
    data['email'] = this.email;
    data['model'] = this.model;
    data['category'] = this.category;
    data['created_at'] = this.createdAt;
    data['updated_at'] = this.updatedAt;
    return data;
  }
}