from article on evalvite, example 3 models from dist

models.ts

// file: example3/models.ts
// model for one input box
export interface NumberModelItem {
  [key: string]: any;
  value: Attribute<number>;
}
// … other models omitted
export default class NumberModel {
  [key: string]: any;
  // array content has to be an object, can't be just ArrayAttribute<number>; see NaiveArrayAttribute if you want to do an array of number
  content: ArrayAttribute<NumberModelItem>;
  isDefined: Attribute<boolean>;
  number: Attribute<number>;
  average: Attribute<number>;
  sum: Attribute<number>;
  max: Attribute<number>;
  constructor() {
    this.content = ev.array<NumberModelItem>("content");
    // how many items
    this.number = ev.computed<number>(
      (values: NumberStateItem[]) => {
        return values.length;
      },
      [this.content],
      "number"
    );
    // is it zero length?
    this.isDefined = ev.computed<boolean>(
      (n: number): boolean => {
        return n > 0;
      },
      [this.number],
      "isDefined"
    );
    // sum
    this.sum = ev.computed<number>(
      (values: NumberStateItem[]) =>
        values
          .map((nm: NumberStateItem) => nm.value)
          .reduce((prev: number, curr: number) => prev + curr, 0),
      [this.content],
      "sum"
    );
    // avg
    this.average = ev.computed<number>(
      (total: number, howMany: number, divisionOK: boolean): number => {
        if (divisionOK) {
          return total / howMany;
        }
        return 0; // won't matter, user will not see this
      },
      [this.sum, this.number, this.isDefined],
      "average"
    );
    // max
    this.max = ev.computed<number>(
      (values: NumberStateItem[]): number => {
        return values
          .map((nm: NumberStateItem) => nm.value)
          .reduce(
            (prev: number, curr: number) => (prev > curr ? prev : curr),
            0
          );
      },
      [this.content],
      "max"
    );
  }
}