How to iterate formgroup with array in Angular2

Fixed it!!!

So apparently I need to read up on Angular2 Fundamentals because I thought my mistake was legal. Basically, I ignored the square brackets around formGroupName in the tutorial because I've done it numerous times before without issue, but not this time. So to fix I simply added the brackets:

<div formGroupName="i"> => <div [formGroupName]="i">

Here is the solution that worked for me. https://plnkr.co/edit/cs244r

HTML Template:

<div>
      <h2>RegionId: {{regionId}}</h2>
      <h2>Region:  {{region.name}}</h2>
    </div>
    <form [formGroup]="regionFormGroup">
      Region Name: <input type="text" formControlName="regionName" [(ngModel)]="region.name" />
      <div formArrayName="customersArray">
      <table class="simple-table">
        <tr>
          <th>Customer</th>
          <th>Current Period</th>
          <th>Previous Period</th>
        </tr>
        <tbody>
          <tr [formGroupName]="i" *ngFor="let customerGroup of regionFormGroup.controls.customersArray.controls; let i = index">
            <td>{{region.customers[i].name}} - index {{i}}</td>
            <td><input type="text" formControlName="currentPeriod" [(ngModel)]="region.customers[i].currentPeriod"/></td>
            <td><input type="text" formControlName="previousPeriod" [(ngModel)]="region.customers[i].previousPeriod"></td>
          </tr>
        </tbody>
      </table>
      </div> <!-- end: div FormArrayName -->
    </form>

Component.ts

export class AppComponent  implements OnInit {

  regionId: number = 5;
  region: RegionModel;
  regionFormGroup: FormGroup;

  constructor( private customerService: CustomerService,private fb: FormBuilder) {  }

  ngOnInit(): void {

    // initialize form
    this.regionFormGroup = new FormGroup({
      regionName: new FormControl(''),
      customersArray: new FormArray([])
    });

    // Retrieve data from datasource
    this.customerService.getCustomerByRegion(5)
      .subscribe( (reg: RegionModel )  => {
        this.region = reg;
        this.buildForm();
      });
  }

  buildForm = () : void => {

    const customersControls = <FormArray>this.regionFormGroup.controls['customersArray'];

    this.region.customers.forEach( (cust : CustomerModel) => {
      customersControls.push(this.createCustomerFormGroup(cust));
       console.log(customersControls);
    });
  }

  createCustomerFormGroup(cust: CustomerModel) {

        return this.fb.group({
            currentPeriod: [''],
            previousPeriod: ['']
        });
    }
}