Переменная от сервиса к компоненту пуста, код состояния 304 HTTP GET

Question

У меня есть компонент center-prices.component.ts

import { Component, OnInit } from '@angular/core';
import { ActivatedRoute } from '@angular/router';
import { PriceRule } from '../models/price-rule';
import { PriceRulesService } from '../services/price-rules.service'

@Component({
  selector: 'app-center-prices',
  templateUrl: './center-prices.component.html',
  providers: [PriceRulesService],
  styles: [`
  nb-card {
    width: 300px;
  }
  nb-select {
    width: 125px;
  }`],
})

export class CenterPricesComponent implements OnInit {

  centerprices: PriceRule[];
  pricerule: PriceRule;
  errorMessage: string;

  constructor(
    private priceruleService: PriceRulesService,
    private route: ActivatedRoute
  ) {}

  ngOnInit() {
    this.getPriceRule();
  }

  getPriceRule() {
    //const id = this.route.snapshot.paramMap.get('id');
    this.priceruleService.getPriceRule('1')
      .subscribe(
        pricerule => this.pricerule = pricerule
      );
  }
}

Услуга:

import { Injectable } from '@angular/core';
import { PriceRule } from '../models/price-rule';
import { HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';

@Injectable()

export class PriceRulesService {

    private url: string = 'http://localhost:5555/price_rules';

    constructor(private http: HttpClient) {
        this.http = http;
    }

    getPriceRules(): Observable<PriceRule[]> {
        return this.http.get<PriceRule[]>(this.url);
    }

    getPriceRule(id: string): Observable<PriceRule> {
        return this.http.get<PriceRule>(`${this.url}/${id}`)
        .map(response => PriceRule.fromJson(response));
    }

    addPriceRule(p: PriceRule) {
        return this.http.post(this.url, p);
    }

    delPriceRule(id: string) {
        return this.http.delete<PriceRule>(`${this.url}/${id}`);
    }
}

Я использую поддельный json-сервер благодаря пакету npm json-server вот так: sudo json-server -p 5555 price_rules.json

price_rules.json:

{
  "price_rules": [
    {
      "id": "1",
      "activity": "Tennis",
      "duration": 45,
      "is_indoor": false,
      "surface": "code",
      "hour_start": "08:00",
      "hour_end": "17:00",
      "price": 1500,
      "currency": "EUR",
      "weekdays": [
        1,
        2,
        3,
        4,
        5,
        6,
        7
      ]
    },
    {
      "id": "2",
      "activity": "Badminton",
      "duration": 90,
      "is_indoor": true,
      "surface": "code",
      "hour_start": "10:00",
      "hour_end": "18:00",
      "price": 1600,
      "currency": "EUR",
      "weekdays": [
        1,
        2,
        3,
        4,
        5
      ]
    }
  ]
}

Сервер работает, моя проблема, когда я console.log pricerule в компоненте, это результат в консоли: {}

Когда я console.log response в функции getPriceRule службы, все детали, которые мне нужны, отображаются в консоли.

Вот класс PriceRule

export class PriceRule {

    public static fromJson(json: Object): PriceRule {

        return new PriceRule(
            json['id'],
            json['activity'],
            json['duration'],
            json['is_indoor'],
            json['surface'],
            json['hour_start'],
            json['hour_end'],
            json['price'],
            json['currency'],
            json['weekdays']
        );
    } 

    constructor(
        id: string,
        activity: string,
        duration: number,
        is_indoor: boolean,
        surface: string,
        hour_start: string,
        hour_end: string,
        price: number,
        currency: string,
        weekdays: number[]
    ){ }
}

Я также заметил, что GET возвращает код 304 Not modified в консоли в разделе networks