I'm having trouble accessing the first element of an undefined property in Angular 2, resulting in an error message. The error context is shown as [object Object]

My service functions in the following way:

getRecords(): Observable<any>{
    return this.http.get(this.fetchAdminData)
                    .map(this.extractData)
                    .catch(this.handleError);
  }

The extraction of data happens like this:

private extractData(res: Response) {
    let body = res.json();
    return body || { };
  }

In my component, I make the call as shown below:

import {Component, OnInit} from '@angular/core'
import {FormsHandler} from '../services/service.forms'


@Component({
  selector: 'form-admin',
  templateUrl: '../partials/form5.html'
})

export class FormAdminComponent implements OnInit {
  public records
  constructor(private formHandler : FormsHandler){
  }

  ngOnInit(){
    this.formHandler.getRecords().subscribe(res => {
      if (res.ok){
        this.records = res.data
        console.log(res)
        console.log(this.records[0])
      }
    })
  }

}

However, when I include it in the HTML like this, errors occur:

{{records}} // This works perfectly 
    {{records[0]}}  //Cannot read property '0' of undefined ERROR CONTEXT:    [object Object]

Moreover, even accessing nested objects poses a challenge:

<tr *ngFor="let record of records">
              <td>{{record.firstName + " "+ record.middleName+ " "+ record.LastName}}</td>
              <td>{{record.BankingDetails.company}} </td> // This results in errorTypeError: Cannot read property 'company' of undefined
              <td>{{record.BankingDetails}} </td> //working fine but resulting in [object Object]

              <td>Pending</td>
              </td>
            </tr>

This leads to TypeError: Cannot read property 'company' of undefined

The response object looks like this:

Object {ok: true, data: Array[2]}

The complete data structure is as follows :

[
 {
"Address": {
"addressLine1":  "nh" ,
"addressLine2":  "nghn" ,
"city":  "ngh" ,
"formStatus": 2 ,
"pinCode":  "ngh" ,
"state":  "nghn"
} ,
"BankingDetails": {
"bankName":  "csdcss" ,
"company":  "cd" ,
"designation":  "kn" ,
"loanAmount":  "csd" ,
"loanPurpose":  "cs" ,
"panCardNumber":  "84894848" ,
"salary":  "55"
} ,
"contact":  "vsd" ,
"date":  "vsd" ,
"dob": Mon Jan 01 1 00:00:00 GMT+00:00 ,
"email": <a href="/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="fb9a99939288939e90bb9c969a9297d5989496">[email protected]</a>, »
"firstName":  "cs" ,
"firstname":  "" ,
"formStatus": 3 ,
"gender":  "male" ,
"id":  "98fd72b9-62fe-4fcd-90d6-f2a5f83c052b" ,
"isAdmin": 1 ,
"lastName":  "vs" ,
"lastname":  "" ,
"middleName":  "vds" ,
"middlename":  "" ,
"month":  "vsd" ,
"password": <binary, 60 bytes, "24 32 61 24 31 30..."> ,
"username":  "" ,
"year":  "vs"
},
...
]

I am struggling to understand why I can print JSON using console.log but cannot access it via HTML.

Furthermore, when I use

{{records}} 

it shows up as [object Object]. Therefore, I have to add

{{records | json}}

to view the complete data.

Please advise on what I might be doing wrong, as I aim to access nested elements like records.BankingDetails.company.

Answer №1

When fetching records asynchronously, Angular may encounter an issue where the bindings are resolved before records is assigned a value, causing records[0] to fail.

To avoid this, you can utilize the following syntax:

{{records && records[0]}}

For other expressions, consider using the safe-navigation (Elvis) operator, like so:

{{records?.someprop}}

However, be aware that there is no safe-navigation equivalent for array index access (?[]).

Answer №2

After receiving guidance from @Akshay Rao, I was able to find a solution to the problem. I implemented these suggestions in order to ensure data availability before the page is rendered

<div *ngIf="records">
</div>

Furthermore, following advice from @Günter Zöchbauer, I utilized the (Elvis) operator like so:

{{record.BankingDetails?.company}}

This implementation proved successful. Thank you.

Answer №3

The data starts off as null but is populated once the server responds

It is recommended to use the following code snippet:

{{ records }}

{{records && records[0]}}

Answer №4

  1. When encountering [object object], it is important to first convert the content into a string and then parse it as shown below...

var data = JSON.parse(JSON.stringify(records));

  1. If you need to access nested elements, there are two options available... 2(a). You can either initialize them as empty arrays or objects, although this may not be ideal.
on initialization :-
records.bankingDetails = {};

2(b). The recommended approach by the angular team is to use ngIf on the parent div where the nested elements are being used.

This should meet your needs :)

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