我如何在 dart 中调用泛型类型的方法

Question

There are several models have a same structure, { type: xxx, settings: xxx}, so i would like to use a parent class "WidgetConfig" with a generic type "T" to implement this, but problem occurs when i add "fromJson" methods. How can i invoke method on a generic type or any other ways to implement this?

class BannerWidgetViewModel extends ChangeNotifier {
  WidgetConfig<BannerWidgetConfig> config;

  BannerWidgetViewModel(String configJson){
    config = WidgetConfig.fromJson(configJson);
  }
}

class BannerWidgetConfig {
  String imgUrl;
  String padImgUrl;
  String lessonId;

  BannerWidgetConfig.fromJson(json){
    if (json != null) {
      this.imgUrl = json['imgUrl'];
      this.padImgUrl = json['padImgUrl'];
      this.lessonId = json['lessonId'];
    }
  }
}

class WidgetConfig<T> {
  WidgetType type;

  WidgetConfig.fromJson(json){
    if (json != null) {
      this.type = json['type'];
      // this.settings = T.fromJson(json['settings']); // T doesn't have fromJson method
    }
  }
}

---

then i use a abstract class but still not working.

abstract class BaseWidgetConfig {
  BaseWidgetConfig.fromJson(dynamic json);
}

class WidgetConfig<T extends BaseWidgetConfig> {
  WidgetType type;
  T settings;

  WidgetConfig.fromJson(json){
    if (json != null) {
      this.type = json['type'];
      this.settings = T.fromJson();
    }
  }
}

code picture

Answer 1

Directly show the function as a reference.

send function as a reference here.

FireStoreHelper.getList<ModelLesson>('grade4', ModelLesson.fromJson);

get the method here.

static Future<List<T>> getList<T>(String path, Function fromJson)