Angular - Issue: Attempting to access properties on undefined (specifically 'forEach')

I'm attempting to access the roles array from this object but encountering the following error:

TypeError: Cannot read properties of undefined (reading 'forEach')

Here is the code snippet causing the issue:

this.data.roles.forEach(role => {

  this.roleIds.push(role.id); // roleIds is a separate array of numbers that I've created.

})

The data object looks like this:

{
    "userID": "abcd",
    "firstName": "FNU",
    "lastName": "LNU",
    "allowedOffices": [
        {
            "roles":[ 
                {
                    "id":"ABC",
                    "name": "Read"
                },
                {
                    "id":"XYZ",
                    "name": "Write"
                }
            ]
        }
    ]
}

this.data.roles.forEach(role => {

  this.roleIds.push(role.id); // roleIds is another array of numbers I have defined.

})

Answer №1

Upon analyzing your code, it appears that the issue may be related to how you are defining the array within the Angular lifecycle.

export class Component implements OnInit {
  data: any; // Alternatively, if you prefer to specify a type for your JSON data
  roleIds: any = [];

  constructor() {
      this.data = // Insert your JSON data here
  }

  ngOnInit() {
    this.data.roles.forEach(role => {
        this.roleIds.push(role.id);
     }
  }
}

You could also consider using an interface if you encounter other issues while working with the JSON object. Something like the following example might suit your needs:

interface UserData {
  userID: string;
  firstName: string;
  allowedOffices: any[];
  lastName: string;
  roles: {
    id: string;
    name: string;
  }[];
}

Please note that in your provided snippet, the allowedOffices property lacks a closing bracket. This could imply that you are unable to access roles from your current location (i.e., you may need to reference this.data.allowedOffices.roles to fetch the desired data).

I hope this explanation proves helpful! ✨

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