问HttpClient在Angular 6中未检索json数据

EN

btc = this.http.get<any>(this.btcurl).subscribe(res => this.btc = res);

  eth = this.http.get<any>(this.ethurl).subscribe(res => this.eth = res);

  ltc = this.http.get<any>(this.ltcurl).subscribe(res => this.ltc = res);

  progressInfoData = [
    {
      title: 'Bitcoin (BTC) Price',
      value: this.btc,
      activeProgress: 70,
      description: 'Better than last week (70%)',
    },
    {
      title: 'Ethereum (ETH) Price',
      value: this.eth,
      activeProgress: 30,
      description: 'Better than last week (30%)',
    },
    {
      title: 'Litecoin (LTC) Price',
      value: this.ltc,
      activeProgress: 55,
      description: 'Better than last week (55%)',
    },
  ];

<nb-card size="medium">
  <nb-card-body>
    <div class="progress-info" *ngFor="let item of progressInfoData | async">
      <div class="title">{{ item.title }}</div>
      <div class="value">{{ item.value.EUR }}</div>
      <nb-progress-bar [value]="item.activeProgress"></nb-progress-bar>
      <div class="description">
        <bdi>{{ item.description }}</bdi>
      </div>
    </div>
  </nb-card-body>
</nb-card>

 <div class="value">{{ btc.EUR }}</div>