type 'null' is not a subtype of type 'map string dynamic ' flutter

Question

I'm trying to use the API in my application it works normally, but when JSON gets null the app doesn't work.

works normally:

{
   "product":{
      "description_1":"Lorem Ipsum is simply dummy text of the printing and typesetting industry.",
      "description_2":"Contrary to popular belief, Lorem Ipsum is not simply random text. It has roots in a piece of classical Latin literature from 45 BC, making it over 2000 years old.",
      "description_3":"There are many variations of passages of Lorem Ipsum available, but the majority have suffered alteratenter code hereion in some form",

   }
}

Error: "type 'null' is not a subtype of type 'map string dynamic ' ":

{ "product":null }

Class:

class Store {
  Store({
    required this.product,
  });

  Product product;

  factory Store.fromJson(Map<String, dynamic> json) => Store(
        product: Product.fromJson(json["product"]),
      );

  Map<String, dynamic> toJson() => {
        "product": product.toJson(),
      };
}

class Product {
  Product({
    required this.description1,
    required this.description2,
    required this.description3,
  });

  String description1;
  String description2;
  String description3;

  factory Product.fromJson(Map<String, dynamic> json) => Product(
        description1: json["description_1"] ?? "",
        description2: json["description_2"] ?? "",
        description3: json["description_3"] ?? "",
      );

  Map<String, dynamic> toJson() => {
        "description_1": description1,
        "description_2": description2,
        "description_3": description3,
      };
}

lepsch · Accepted Answer · 2022-09-14 23:46:48Z

2

If product can actually be null then Store needs to deal with it. Change the Store class product property to be nullable with ? symbol like the following:

class Store {
  Store({
    this.product,
  });

  Product? product;

  factory Store.fromJson(Map<String, dynamic> json) => Store(
        product: json["product"] != null 
            ? Product.fromJson(json["product"])
            : null,
      );

  Map<String, dynamic> toJson() => {
        "product": product?.toJson(),
      };
}

answered Sep 14, 2022 at 23:46

lepsch

10.5k5 gold badges33 silver badges48 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Rodrigues silva Over a year ago

Thanks for the answer. But the parameters "description_1", "description_2", "description_3", "description_4", "description_5", are not sent and product receives only "null" it still has an error.

Chance Over a year ago

Just correct the answer from json["product"] != null to json["product"] is Map.

lepsch Over a year ago

@Rodriguessilva, is the JSON like this? {"product": null}?

Rodrigues silva Over a year ago

@lepsch Yes, some JSON comes without description_1, description_2, description_3. only NULL

lepsch Over a year ago

The solution I gave should deal with this situation smoothly. Isn't it enough? What exactly are you looking for if product == null?

Collectives™ on Stack Overflow

type 'null' is not a subtype of type 'map string dynamic ' flutter

1 Answer 1

5 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Related