Flutter _TypeError (type 'Null' is not a subtype of type 'Map<String, dynamic>')

Question

I am facing an issue with my app, I want to use the WordPress rest API in my flutter application. The problem is when I am trying to Access the UserData model using the CourseData model I am getting an error like that. I want to access the userdata through the course data so that I can get the author's name and details also.

Course Data Model

List<CourseData> courseDataFromJson(String str) =>
    List<CourseData>.from(json.decode(str).map((x) => CourseData.fromJson(x)));

String courseDataToJson(List<CourseData> data) =>
    json.encode(List<dynamic>.from(data.map((x) => x.toJson())));

class CourseData {
  CourseData({
    required this.id,
    required this.date,
    required this.dateGmt,
    required this.guid,
    required this.modified,
    required this.modifiedGmt,
    required this.slug,
    required this.status,
    required this.type,
    required this.link,
    required this.title,
    required this.content,
    required this.excerpt,
    required this.author,
    required this.featuredMedia,
    required this.template,
    required this.courseCategory,
    required this.courseTag,
    required this.links,
    required this.authordata,
  });
  int id;
  DateTime date;
  DateTime dateGmt;
  Guid guid;
  DateTime modified;
  DateTime modifiedGmt;
  String slug;
  String status;
  String type;
  String link;
  Guid title;
  Content content;
  Content excerpt;
  int author;
  int featuredMedia;
  String template;
  List<int> courseCategory;
  List<int> courseTag;
  Links links;
  UsersData authordata;

  factory CourseData.fromJson(Map<String, dynamic> json) => CourseData(
        id: json["id"],
        date: DateTime.parse(json["date"]),
        dateGmt: DateTime.parse(json["date_gmt"]),
        guid: Guid.fromJson(json["guid"]),
        modified: DateTime.parse(json["modified"]),
        modifiedGmt: DateTime.parse(json["modified_gmt"]),
        slug: json["slug"],
        status: json["status"],
        type: json["type"],
        link: json["link"],
        title: Guid.fromJson(json["title"]),
        content: Content.fromJson(json["content"]),
        excerpt: Content.fromJson(json["excerpt"]),
        author: json["author"],
        featuredMedia: json["featured_media"],
        template: json["template"],
        courseCategory: List<int>.from(json["course-category"].map((x) => x)),
        courseTag: List<int>.from(json["course-tag"].map((x) => x)),
        links: Links.fromJson(json["_links"]),
        authordata: UsersData.fromJson(json["authordata"]),
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "date": date.toIso8601String(),
        "date_gmt": dateGmt.toIso8601String(),
        "guid": guid.toJson(),
        "modified": modified.toIso8601String(),
        "modified_gmt": modifiedGmt.toIso8601String(),
        "slug": slug,
        "status": status,
        "type": type,
        "link": link,
        "title": title.toJson(),
        "content": content.toJson(),
        "excerpt": excerpt.toJson(),
        "author": author,
        "featured_media": featuredMedia,
        "template": template,
        "course-category": List<dynamic>.from(courseCategory.map((x) => x)),
        "course-tag": List<dynamic>.from(courseTag.map((x) => x)),
        "_links": links.toJson(),
        "authordata": authordata.toJson(),
      };
}

class Content {
  Content({
    required this.rendered,
    required this.protected,
  });

  String rendered;
  bool protected;

  factory Content.fromJson(Map<String, dynamic> json) => Content(
        rendered: json["rendered"],
        protected: json["protected"],
      );

  Map<String, dynamic> toJson() => {
        "rendered": rendered,
        "protected": protected,
      };
}

class Guid {
  Guid({
    required this.rendered,
  });

  String rendered;

  factory Guid.fromJson(Map<String, dynamic> json) => Guid(
        rendered: json["rendered"],
      );

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

class Links {
  Links({
    required this.self,
    required this.collection,
    required this.about,
    required this.author,
    required this.wpFeaturedmedia,
    required this.wpAttachment,
    required this.wpTerm,
    required this.curies,
  });

  List<About> self;
  List<About> collection;
  List<About> about;
  List<Author> author;
  List<Author> wpFeaturedmedia;
  List<About> wpAttachment;
  List<WpTerm> wpTerm;
  List<Cury> curies;

  factory Links.fromJson(Map<String, dynamic> json) => Links(
        self: List<About>.from(json["self"].map((x) => About.fromJson(x))),
        collection:
            List<About>.from(json["collection"].map((x) => About.fromJson(x))),
        about: List<About>.from(json["about"].map((x) => About.fromJson(x))),
        author:
            List<Author>.from(json["author"].map((x) => Author.fromJson(x))),
        wpFeaturedmedia: List<Author>.from(
            json["wp:featuredmedia"].map((x) => Author.fromJson(x))),
        wpAttachment: List<About>.from(
            json["wp:attachment"].map((x) => About.fromJson(x))),
        wpTerm:
            List<WpTerm>.from(json["wp:term"].map((x) => WpTerm.fromJson(x))),
        curies: List<Cury>.from(json["curies"].map((x) => Cury.fromJson(x))),
      );

  Map<String, dynamic> toJson() => {
        "self": List<dynamic>.from(self.map((x) => x.toJson())),
        "collection": List<dynamic>.from(collection.map((x) => x.toJson())),
        "about": List<dynamic>.from(about.map((x) => x.toJson())),
        "author": List<dynamic>.from(author.map((x) => x.toJson())),
        "wp:featuredmedia":
            List<dynamic>.from(wpFeaturedmedia.map((x) => x.toJson())),
        "wp:attachment":
            List<dynamic>.from(wpAttachment.map((x) => x.toJson())),
        "wp:term": List<dynamic>.from(wpTerm.map((x) => x.toJson())),
        "curies": List<dynamic>.from(curies.map((x) => x.toJson())),
      };
}

class About {
  About({
    required this.href,
  });

  String href;

  factory About.fromJson(Map<String, dynamic> json) => About(
        href: json["href"],
      );

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

class Author {
  Author({
    required this.embeddable,
    required this.href,
  });

  bool embeddable;
  String href;

  factory Author.fromJson(Map<String, dynamic> json) => Author(
        embeddable: json["embeddable"],
        href: json["href"],
      );

  Map<String, dynamic> toJson() => {
        "embeddable": embeddable,
        "href": href,
      };
}

class Cury {
  Cury({
    required this.name,
    required this.href,
    required this.templated,
  });

  String name;
  String href;
  bool templated;

  factory Cury.fromJson(Map<String, dynamic> json) => Cury(
        name: json["name"],
        href: json["href"],
        templated: json["templated"],
      );

  Map<String, dynamic> toJson() => {
        "name": name,
        "href": href,
        "templated": templated,
      };
}

class WpTerm {
  WpTerm({
    required this.taxonomy,
    required this.embeddable,
    required this.href,
  });

  String taxonomy;
  bool embeddable;
  String href;

  factory WpTerm.fromJson(Map<String, dynamic> json) => WpTerm(
        taxonomy: json["taxonomy"],
        embeddable: json["embeddable"],
        href: json["href"],
      );

  Map<String, dynamic> toJson() => {
        "taxonomy": taxonomy,
        "embeddable": embeddable,
        "href": href,
      };
}

User Data Model

List<UsersData> usersDataFromJson(String str) =>
    List<UsersData>.from(json.decode(str).map((x) => UsersData.fromJson(x)));

String usersDataToJson(List<UsersData> data) =>
    json.encode(List<dynamic>.from(data.map((x) => x.toJson())));

class UsersData {
  UsersData({
    required this.id,
    required this.name,
    required this.url,
    required this.description,
    required this.link,
    required this.slug,
    required this.avatarUrls,
    required this.meta,
    required this.isSuperAdmin,
    required this.woocommerceMeta,
    required this.links,
  });

  int id;
  String name;
  String url;
  String description;
  String link;
  String slug;
  Map<String, String> avatarUrls;
  List<dynamic> meta;
  bool isSuperAdmin;
  WoocommerceMeta woocommerceMeta;
  Links links;

  factory UsersData.fromJson(Map<String, dynamic> json) => UsersData(
        id: json["id"],
        name: json["name"],
        url: json["url"],
        description: json["description"],
        link: json["link"],
        slug: json["slug"],
        avatarUrls: Map.from(json["avatar_urls"])
            .map((k, v) => MapEntry<String, String>(k, v)),
        meta: List<dynamic>.from(json["meta"].map((x) => x)),
        isSuperAdmin: json["is_super_admin"],
        woocommerceMeta: WoocommerceMeta.fromJson(json["woocommerce_meta"]),
        links: Links.fromJson(json["_links"]),
      );

  Map<String, dynamic> toJson() => {
        "id": id,
        "name": name,
        "url": url,
        "description": description,
        "link": link,
        "slug": slug,
        "avatar_urls":
            Map.from(avatarUrls).map((k, v) => MapEntry<String, dynamic>(k, v)),
        "meta": List<dynamic>.from(meta.map((x) => x)),
        "is_super_admin": isSuperAdmin,
        "woocommerce_meta": woocommerceMeta.toJson(),
        "_links": links.toJson(),
      };
}

class Links {
  Links({
    required this.self,
    required this.collection,
  });

  List<Collection> self;
  List<Collection> collection;

  factory Links.fromJson(Map<String, dynamic> json) => Links(
        self: List<Collection>.from(
            json["self"].map((x) => Collection.fromJson(x))),
        collection: List<Collection>.from(
            json["collection"].map((x) => Collection.fromJson(x))),
      );

  Map<String, dynamic> toJson() => {
        "self": List<dynamic>.from(self.map((x) => x.toJson())),
        "collection": List<dynamic>.from(collection.map((x) => x.toJson())),
      };
}

class Collection {
  Collection({
    required this.href,
  });

  String href;

  factory Collection.fromJson(Map<String, dynamic> json) => Collection(
        href: json["href"],
      );

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

class WoocommerceMeta {
  WoocommerceMeta({
    required this.activityPanelInboxLastRead,
    required this.activityPanelReviewsLastRead,
    required this.categoriesReportColumns,
    required this.couponsReportColumns,
    required this.customersReportColumns,
    required this.ordersReportColumns,
    required this.productsReportColumns,
    required this.revenueReportColumns,
    required this.taxesReportColumns,
    required this.variationsReportColumns,
    required this.dashboardSections,
    required this.dashboardChartType,
    required this.dashboardChartInterval,
    required this.dashboardLeaderboardRows,
    required this.homepageLayout,
    required this.homepageStats,
    required this.taskListTrackedStartedTasks,
    required this.helpPanelHighlightShown,
    required this.androidAppBannerDismissed,
  });

  String activityPanelInboxLastRead;
  String activityPanelReviewsLastRead;
  String categoriesReportColumns;
  String couponsReportColumns;
  String customersReportColumns;
  String ordersReportColumns;
  String productsReportColumns;
  String revenueReportColumns;
  String taxesReportColumns;
  String variationsReportColumns;
  String dashboardSections;
  String dashboardChartType;
  String dashboardChartInterval;
  String dashboardLeaderboardRows;
  String homepageLayout;
  String homepageStats;
  String taskListTrackedStartedTasks;
  String helpPanelHighlightShown;
  String androidAppBannerDismissed;

  factory WoocommerceMeta.fromJson(Map<String, dynamic> json) =>
      WoocommerceMeta(
        activityPanelInboxLastRead: json["activity_panel_inbox_last_read"],
        activityPanelReviewsLastRead: json["activity_panel_reviews_last_read"],
        categoriesReportColumns: json["categories_report_columns"],
        couponsReportColumns: json["coupons_report_columns"],
        customersReportColumns: json["customers_report_columns"],
        ordersReportColumns: json["orders_report_columns"],
        productsReportColumns: json["products_report_columns"],
        revenueReportColumns: json["revenue_report_columns"],
        taxesReportColumns: json["taxes_report_columns"],
        variationsReportColumns: json["variations_report_columns"],
        dashboardSections: json["dashboard_sections"],
        dashboardChartType: json["dashboard_chart_type"],
        dashboardChartInterval: json["dashboard_chart_interval"],
        dashboardLeaderboardRows: json["dashboard_leaderboard_rows"],
        homepageLayout: json["homepage_layout"],
        homepageStats: json["homepage_stats"],
        taskListTrackedStartedTasks: json["task_list_tracked_started_tasks"],
        helpPanelHighlightShown: json["help_panel_highlight_shown"],
        androidAppBannerDismissed: json["android_app_banner_dismissed"],
      );

  Map<String, dynamic> toJson() => {
        "activity_panel_inbox_last_read": activityPanelInboxLastRead,
        "activity_panel_reviews_last_read": activityPanelReviewsLastRead,
        "categories_report_columns": categoriesReportColumns,
        "coupons_report_columns": couponsReportColumns,
        "customers_report_columns": customersReportColumns,
        "orders_report_columns": ordersReportColumns,
        "products_report_columns": productsReportColumns,
        "revenue_report_columns": revenueReportColumns,
        "taxes_report_columns": taxesReportColumns,
        "variations_report_columns": variationsReportColumns,
        "dashboard_sections": dashboardSections,
        "dashboard_chart_type": dashboardChartType,
        "dashboard_chart_interval": dashboardChartInterval,
        "dashboard_leaderboard_rows": dashboardLeaderboardRows,
        "homepage_layout": homepageLayout,
        "homepage_stats": homepageStats,
        "task_list_tracked_started_tasks": taskListTrackedStartedTasks,
        "help_panel_highlight_shown": helpPanelHighlightShown,
        "android_app_banner_dismissed": androidAppBannerDismissed,
      };
}

Any Help will be appreciated.

Answer 1

Checking the url https://egiye.com/wp-json/wp/v2/courses (shared in comment) I don't see any authordata prop, so that is why flutter is telling you that it is expecting a map but it receives a null value instead.