Can't call method of an object that is part of the observable array

[BornaGajic]

Hi!
I'm trying to update an element in the observable array by accessing it and calling a method that updates it.
But I'm getting Unhandled Rejection (TypeError): item.changeData is not a function. I'm using Typescript with React.

(...)
  service: IServices;

  myTasks: Task[] = [];
  favBusinesses: IBusiness[] = [];

  constructor (service: IServices)
  {
      makeAutoObservable(this, { service: false });

      this.service = service;
  }

  async updateMyTask (newTask: TaskCrud): Promise<void>
  {
      // Void service method that updates the task on the server
      //await this.service.taskService.updateTask(newTask);
  
      runInAction(() => {
          this.myTasks.forEach( (item, idx) => {
              if(item.id === newTask.id)
              {
                  item.changeData({ description: "Some description" } as ITask); // <===== Error
              }
          });

          // If i update it like this then it works!
          // x.highPrice = 100000;
          //x.description = "This works";
      });

      console.log(JSON.stringify(this.myTasks.find(x => x.id === newTask.id))) // --> It's not null!
  }

changeData is a method of the Task class that updates it's fields (which is also made observable with makeAutoObservable)

  changeData (data: ITask): void
  {
      this.description = data.description ?? this.description;
      this.lowPrice = data.lowPrice ?? this.lowPrice;
      this.highPrice = data.highPrice ?? this.highPrice;
      this.username = data.username ?? this.username;
      this.email = data.email ?? this.email;
  }

TaskCrud

export interface TaskCrud
{
    description?: string;
    highPrice?: number;
    lowPrice?: number;

    id?: string;
}

[mweststrate]

I can't spot an obvious problem with this, so for any help a reproduction is needed. The most likely problem is that you have some plain json objects in your myTasks collection, that are not actual Task class instances, so they will have the id etc fields, but not a changeData method. I'd check any code that fills the collection.

[BornaGajic]

The most likely problem is that you have some plain json objects in your myTasks collection, that are not actual Task class instances,

This was the problem, thanks! :)