<String, dynamic>' is not a subtype of type 'List<dynamic>' flutter

问题

Here is my sample json response

{
  "billing": [
    {
      "id": 1,
      "add_id": 23
    }
  ],
  "shipping": [
    {
      "id": 2,
      "add_id": 345
    },
    {
      "id": 3,
      "add_id": 345
    }
  ]
}

Here is my api receiving part

      List responseList = response.data['data'];//getting api response after decode
      List<AddressListGroupModel> listData =
          responseList.map((f) => AddressListGroupModel.fromJson(f)).toList();
      return listData;

Here is my model

class AddressListGroupModel {
  List<Add> billing;
  List<Add> shipping;
 

  AddressListGroupModel({this.billing, this.shipping, this.billingShipping});

  AddressListGroupModel.fromJson(Map<String, dynamic> json) {
    billing = List<Add>.from(json["billing"].map((x) => Add.fromJson(x)));
    shipping = List<Add>.from(json["shipping"].map((x) => Add.fromJson(x)));
 
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['billing'] = List<dynamic>.from(billing.map((x) => x.toJson()));
    data['shipping'] = List<dynamic>.from(shipping.map((x) => x.toJson()));

    return data;
  }
}

class Add {
  int id;
  int addId;
  
  Add({
    this.id,
    this.addId,
   
  });

  Add.fromJson(Map<String, dynamic> json) {
    id = json["id"];
    userId = json["add_id"];
   
  }

  Map<String, dynamic> toJson() {
    final Map<String, dynamic> data = new Map<String, dynamic>();
    data['id'] = this.id;
    data['add_id'] = this.userId;
    return data;
  }
}

I need to map the response to the model , I am getting error since response is coming as object .. So how can I map this response .. Please help to fix the issue

I am getting error in List responseList = response.data['data'] since it is coming as a object

回答1:

You are trying to map an array when your response is a json. You must use this variable for doing the mapping.

Map<String, dynamic> resp = response.data;
AddressListGroupModel addressListGroupModel = AddressListGroupModel.fromJson(resp);

Because your json only gives one value and not a list of addresses.

回答2:

You cannot automatically add the Json output to the list. Use this;

AddressListGroupModel.fromJson(response.data);

回答3:

{ //<-- Map
  "billing": [  //<-- List
    { // <-- Map
      "id": 1,
      "add_id": 23
    }
  ],
  "shipping": [// <-- List
    { // <-- Map
      "id": 2,
      "add_id": 345
    },
    {
      "id": 3,
      "add_id": 345
    }
  ]
}

I think your response[data] returns a single Map so you can just replace Map instead of List.

Map data = response[data];
AddressListGroupModel model = AddressListGroupModel.fromMap(data);

or incase it returns a List.

final data = response[data] as Map;
List<AddressListGroupModel> listData =
          responseList.map((f) => AddressListGroupModel.fromMap(f)).toList();
return listData;

This is how Your code should look like

class AddressListGroupModel {
  final List<Add> billing;
  final List<Add> shipping;

  AddressListGroupModel({
    this.billing,
    this.shipping,
  });

  // to know more about factory constructor
  // read https://dart.dev/guides/language/language-tour#constructors
  factory AddressListGroupModel.fromMap(Map<String, dynamic> map) {
    if (map == null) return null;

    return AddressListGroupModel(
      billing: List<Add>.from(map['billing']?.map((x) => Add.fromMap(x))),
      shipping: List<Add>.from(map['shipping']?.map((x) => Add.fromMap(x))),
    );
  }

  Map<String, dynamic> toMap() {
    return {
      'billing': billing?.map((x) => x?.toMap())?.toList(),
      'shipping': shipping?.map((x) => x?.toMap())?.toList(),
    };
  }

  AddressListGroupModel copyWith({
    List<Add> billing,
    List<Add> shipping,
  }) {
    return AddressListGroupModel(
      billing: billing ?? this.billing,
      shipping: shipping ?? this.shipping,
    );
  }
}

class Add {
  final int id;
  // assuming this is userId instead of addId.
  final int userId;

  Add({
    this.id,
    this.userId,
  });

  factory Add.fromMap(Map<String, dynamic> map) {
    if (map == null) return null;

    return Add(
      id: map['id'],
      userId: map['userId'],
    );
  }

  Map<String, dynamic> toJson() {
    return {
      'id': id,
      'userId': userId,
    };
  }
}

来源：https://stackoverflow.com/questions/65796626/string-dynamic-is-not-a-subtype-of-type-listdynamic-flutter