Getting this error: "The argument type 'Object?' can't be assigned to the parameter type 'List<Map<String, Object>>'."

i want to try to make models. And here’s the code

...

class TutorialStep {
  String step;
  String description;
  TutorialStep({required this.step, required this.description});

  Map<String, Object> toMap() {
    return {
      'step': step,
      'description': description,
    };
  }

  factory TutorialStep.fromJson(Map<String, Object> json) => TutorialStep(
        step: json['step'] as String,
        description: json['description'] as String,
      );

  static List<TutorialStep> toList(List<Map<String, Object>> json) {
    return List.from(json)
        .map((e) => TutorialStep(step: e['step'], description: e['description'])).toList();
  }
}

class Ingredient {
  String name;
  String size;

  Ingredient({required this.name, required this.size});
  factory Ingredient.fromJson(Map<String, Object> json) => Ingredient(
        name: json['name'] as String,
        size: json['size'] as String,
      );

  Map<String, Object> toMap() {
    return {
      'name': name,
      'size': size,
    };
  }

  static List<Ingredient> toList(List<Map<String, Object>> json) {
    return List.from(json)
        .map((e) => Ingredient(name: e['name'], size: e['size']))
        .toList();
  }
}

and this the recipe_helper.dart:

import 'package:recipe/model/recipe.dart';

class RecipeHelper {
  static List<Recipe> newlyPostedRecipe = newlyPostedRecipeRawData
      .map((data) => Recipe(
            title: data['title'] as String,
            photo: data['photo'] as String,
            description: data['description'] as String,
            tutorial: TutorialStep.toList(data['tutorial']),
            ingredients: Ingredient.toList(data['ingredients']),
          ))
      .toList();
}

the error is in the line tutorial: TutorialStep.toList(data['tutorial']), and ingredients: Ingredient.toList(data['ingredients']), at the recipe_helper.dart

I have tried adding as List at the end of the error, but I still get an error.

So, how to solve the error? Any help would be appreciated. Thanks

>Solution :

Try change

        tutorial: TutorialStep.toList(data['tutorial']),
        ingredients: Ingredient.toList(data['ingredients']),

to

        tutorial: TutorialStep.toList(data['tutorial'] as List<Map<String, Object>>),
        ingredients: Ingredient.toList(data['ingredients'] as List<Map<String, Object>>),