角组件返回未定义

Question

I have a service file that returns two functions with API and array data. Inside a component in the constructor I initiate a service and try to retrieve data onInit in the component, first API function returns and console.log the data without a problem, but the second function getRatings() returns undefined in console.log. Why?

import { Injectable } from '@angular/core';
import { HttpClient } from '@angular/common/http';
import { HttpClientModule } from '@angular/common/http';
import 'rxjs/Rx';


@Injectable()
export class ProductService{
  result:any;
  ratings:any;
  constructor(private http: HttpClient) {}
    getProducts() {
        return this.http.get('https://min-api.cryptocompare.com/data/pricemulti?fsyms=BTC,ETH,IOT,TRX&tsyms=USD').map(result => this.result = result);
      }
    getRatings() {
           return
           [
            {
                imageUrl: "http://loremflickr.com/150/150?random=1",
                productName: "Product 1",
                releasedDate: "May 31, 2016",
                description: "Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin commodo. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.",
                rating: 4,
                numOfReviews: 2
            },
            {
                imageUrl: "http://loremflickr.com/150/150?random=2",
                productName: "Product 2",
                releasedDate: "October 31, 2016",
                description: "Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin commodo. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.",
                rating: 2,
                numOfReviews: 12
            },
            {
                imageUrl: "http://loremflickr.com/150/150?random=3",
                productName: "Product 3",
                releasedDate: "July 30, 2016",
                description: "Cras sit amet nibh libero, in gravida nulla. Nulla vel metus scelerisque ante sollicitudin commodo. Cras purus odio, vestibulum in vulputate at, tempus viverra turpis. Fusce condimentum nunc ac nisi vulputate fringilla. Donec lacinia congue felis in faucibus.",
                rating: 5,
                numOfReviews: 2
            }];
        }
      }

import { Component } from '@angular/core';
import { ProductService } from './product.service';
import { RatingComponent } from './rating.component';
@Component({
  selector: 'crypto',
  styleUrls: ['./app.component.css'],
  template: `<div *ngIf="cryptos">
    <div id="crypto-container" *ngFor="let crypto of objectKeys(cryptos)">
      <span class="left">{{ crypto }}</span>
      <span class="right">{{ cryptos[crypto].USD | currency:'USD':true }}</span>
      <br />
      <rating>
      </rating>
    </div>
  </div>`
})
export class CryptoComponent {
  objectKeys = Object.keys;
cryptos: any;
ratings: any;

constructor(private _data: ProductService) {

}

ngOnInit() {
  this._data.getProducts()
    .subscribe(res => {
      this.cryptos = res;
      console.log(res);
    });
  this.ratings = this._data.getRatings();
    console.log(this.ratings);


}

    onClick($event){
      console.log("Clicked",$event)
    }
}

Answer 1

At the beginning of your getRatings service method, change:

getRatings() {
  return
  [
  // ...

to:

getRatings() {
  return [
  // ...

Explanation : semicolons are implicit on line end in some cases. In your case, your code is interpreted as just return; and the following code is ignored.