Exploring the contents within an array

https://i.sstatic.net/s3Zsn.png

I've encountered an issue with accessing elements of an array in my code. Upon logging the array using :

console.log(MyArray);

The console output displays the content as shown in the image.

The data in this array comes from an API. Rather than accessing it inside the callback function, I aim to use the data later for plotting markers on a map.

However, I am currently facing a roadblock in achieving this.

     private MyArray: any[] = [];
     ngOnInit() {
        this.httpservice.getdata().subscribe
        (data=>
        {this.MyArray.push(data);});

     console.log(MyArray[0]);//My attempt at accessing it here

    var mapProp = {
      center: new google.maps.LatLng(51.508742, -0.120850),
      zoom: 10,
      mapTypeId: google.maps.MapTypeId.ROADMAP
    };
    var map = new google.maps.Map(document.getElementById("googleMap"), 
     mapProp);

    var markerarray: any[] = [];



    //My intention is to eventually access the data here

    for (i = 0; i < 21; i++) {
      markerarray[i] = new google.maps.Marker({
      position: new google.maps.LatLng(MyArray[0][i].latitude, MyArray[i]
     [i].longitude),          //This line
        title: MyArray[1][i].name,  //and this
        map: map
      });


    }

The structure of my httpservice.ts is as follows:

import { Injectable } from '@angular/core';
import { Http } from '@angular/http';
import { Observable } from 'rxjs/Observable';
import { Response, RequestOptions, Headers } from '@angular/http'

@Injectable()
export class HttpService {

    constructor(private hhtp: Http) { }
    getdata() {
        return this.hhtp.get('url').map((res: Response) => { //the url which I am using
            return res.json();
        })

    }

}

Answer №1

It seems that the issue arises from attempting to access your array before the subscribe method has completed its operation.

To resolve this, you can make a simple modification in ngOnInit() and give it a try:

   private MyArray: any[] = [];
   ngOnInit() {
    var mapProp = {
           center: new google.maps.LatLng(51.508742, -0.120850),
           zoom: 10,
           mapTypeId: google.maps.MapTypeId.ROADMAP
    };
    var map = new google.maps.Map(document.getElementById("googleMap"), 
                  mapProp);

   var markerarray: any[] = [];
   this.httpservice.getdata().subscribe(
   (data)=>
   {
     this.MyArray.push(data);
     console.log(MyArray[0]);//Access it here

    //I want to eventually access the data here

    for (i = 0; i < 21; i++) {
      markerarray[i] = new google.maps.Marker({
        position: new google.maps.LatLng(MyArray[0][i].latitude, MyArray[i]
              [i].longitude),          //In this line
        title: MyArray[1][i].name,  //and this
        map: map
      });
    }  // end for
   });  // end subscribe
 } // end ngOninit

The browser console will display the complete data because if you hover over an object 'i' tool tip, it will show 'Value below are evaluated just now'. This indicates that at the time of accessing objects within the array during console logging, they may not have been populated yet.

Answer №2

Are you attempting to access the elements at the right moment? Trying to access them before the service responds will leave MyArray empty.

If you attempt to access an element immediately after receiving the data, you should see it functioning:

private MyArray: any[] = [];
ngOnInit() {
    this.httpservice.getdata().subscribe
    (data=>
    {
     this.MyArray.push(data);

     console.log(MyArray[0][1].name);
    });
}

If you wish to access the data outside of the service method, ensure that the service function has loaded the data first.

You can wait for it using the following approach:

private MyArray: any[] = [];

private IsDataLoaded: boolean = false;

ngOnInit() {
    this.httpservice.getdata().subscribe
    (data=>
    {
     this.MyArray.push(data);
     IsDataLoaded = true;
    });
}

while(true) {
    if(IsDataLoaded) {
        break;
    }
}

// Or alternatively
// while(!IsDataLoaded) {
//    // do nothing but wait
// }

console.log(MyArray[0][1].name);

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