KanbanBoardWebPart04.ts

// ...
import {
  BaseClientSideWebPart,
  IPropertyPaneConfiguration,
  PropertyPaneTextField,
  PropertyPaneDropdown
} from '@microsoft/sp-webpart-base';
import { escape } from '@microsoft/sp-lodash-subset';
// ...

import { ITask } from "./models/ITask";
import { IListInfo } from "./models/IListInfo";
import { IFieldInfo } from "./models/IFieldInfo";
// ...
export default class KanbanBoardWebPart extends BaseClientSideWebPart<IKanbanBoardWebPartProps> {

  private statuses: string[] = [];
  private tasks: ITask[] = [];
  private availableLists: IListInfo[] = [];
  // ...
  private _getAvailableFieldsFromCurrentList(): IFieldInfo[] {
    if (!this.properties.tasksListId)
      return [];

    let filteredListInfo = this.availableLists.filter(l => l.Id == this.properties.tasksListId);
    if (filteredListInfo.length != 1)
      return [];

    return filteredListInfo[0].Fields.filter(f => f.TypeAsString == "Choice");
  }

  protected getPropertyPaneConfiguration(): IPropertyPaneConfiguration {
    return {
      pages: [
        {
          header: {
            description: "Settings"
          },
          groups: [
            {
              groupName: "Tasks source configuration",
              groupFields: [
                PropertyPaneDropdown('tasksListId', {
                  label: "Source Task list",
                  options: this.availableLists.map(l => ({
                    key: l.Id,
                    text: l.Title
                  }))
                }),
                PropertyPaneDropdown('statusFieldName', {
                  label: "Status field Internal name",
                  options: this._getAvailableFieldsFromCurrentList().map(f => ({
                    key: f.InternalName,
                    text: f.Title
                  }))
                })
              ]
            }
          ]
        }
      ]
    };
  }
}