Angular 角度插值语法：从所有子对象中计算所有子对象

我有以下课程：

export class VrpInstance {
  routes: Array<Route>;
}

export class Route {
  points: Array<number>;
}

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如何使用插值语法实现这一点？

您应该避免从模板中调用方法，因为每次运行更改检测时都会调用该方法。如果值可以更改，则应使用管道，因为它不会每次运行角度更改检测，而是仅在值更改时运行

将ArrayVRP实例作为参数的简单管道：

@Pipe({name: 'calculatePoint'})
export class CalculatePointPipe implements PipeTransform {
  transform(route: VrpInstance): number {
    const total = 0;
    route.routes.forEach((points: Array<number>) => {
        total += point.length;
    })
    return total;
  }
}

---

你不应该在html中这样做

@Pipe({name: 'calculatePoint'})
export class CalculatePointPipe implements PipeTransform {
  transform(route: VrpInstance): number {
    const total = 0;
    route.routes.forEach((points: Array<number>) => {
        total += point.length;
    })
    return total;
  }
}

{{ routes | calculatePoint }}