Flutter: 'Null' is not a subtype of type 'String', when calling rest api

Question

I would be highly grateful if the answer is in simple terms. I am a beginner.

here is my full project code: https://drive.google.com/file/d/1nj7Pj7Gzl-xVzzCm-aPRu2H1QUvdjoZB/view?usp=sharing

My error is:

E/flutter (17497): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: type 'Null' is not a subtype of type 'String'
E/flutter (17497): #0      new Welcome.fromJson (package:getx_5_rest_api/models/product.dart:33:22)
E/flutter (17497): #1      welcomeFromJson.<anonymous closure> (package:getx_5_rest_api/models/product.dart:10:60)
E/flutter (17497): #2      MappedListIterable.elementAt (dart:_internal/iterable.dart:413:31)
E/flutter (17497): #3      ListIterator.moveNext (dart:_internal/iterable.dart:342:26)
E/flutter (17497): #4      new List.from (dart:core-patch/array_patch.dart:41:17)
E/flutter (17497): #5      welcomeFromJson (package:getx_5_rest_api/models/product.dart:10:5)
E/flutter (17497): #6      RemoteServices.fetchProducts (package:getx_5_rest_api/services/remote_service.dart:31:14)
E/flutter (17497): <asynchronous suspension>
E/flutter (17497): #7      ProductController.fetchProducts (package:getx_5_rest_api/controllers/product_controller.dart:21:20)
E/flutter (17497): <asynchronous suspension>
E/flutter (17497):

Well, the code part related to this issue would be usefull without having to go through the full repo. About the error, it certainly mean that you try to use a null value somewhere a String is expected. — VincentDR
– VincentDR, Commented Oct 28, 2022 at 13:53

Gwhyyy · Accepted Answer · 2022-10-28 14:18:33Z

1

I found your problem in the JSON response there is an image_link field but in your code inside the :

  factory Welcome.fromJson(Map<String, dynamic> json) => Welcome(
  name: json["name"],
  price: json['price'],
  imageLink: json['imageLink'].toString(),
  rating: json['rating']);

}

you are trying to get imageLink which doesn't exist in the JSON maps List, so it throws null, what exists is image_link and they are not the same so the solution is this : replace the fromJson method with this

      factory Welcome.fromJson(Map<String, dynamic> json) => Welcome(
       name: json["name"],
       price: json['price'],
       imageLink: json['image_link'].toString(),
       rating: json['rating']);
        }

it should now find it.

Hope this helps you.

answered Oct 28, 2022 at 14:18

Gwhyyy

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hamza aboshhiwa · Accepted Answer · 2022-10-28 14:22:15Z

1

in line 22 in product model, you probably entered wrong property in the map, check the response from the API and make sure all the properties match in your fromJson() function

you should use GitHub to share your code, it'll be easier for others to help you when they can just browse the code as easy.

answered Oct 28, 2022 at 14:22

hamza aboshhiwa

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