I want to conditionally apply a css class if the error count in a form is greater than 1. How do I do this in angular4? 

Component:

```
import { Component } from "@angular/core";
import { FormGroup, ReactiveFormsModule, FormBuilder, Validators } from '@angular/forms';

@Component({
    ...
})

export class RegisterComponent {
  complexForm : FormGroup;

  constructor(fb: FormBuilder){
    this.complexForm = fb.group({
      'emailAddress' : [null, Validators.email],
      'firstName': [null, Validators.compose([Validators.required, Validators.minLength(2)])],
      ...
    })
  }

  submitForm(value: any){
    console.log(value);
  }
}

```

Template:

```
<form [formGroup]="complexForm" (ngSubmit)="submitForm(complexForm.value)">
      <section class="form-block">
          <div class="form-group" [ngClass]="{'has-error':!complexForm.controls['emailAddress'].valid && complexForm.controls['emailAddress'].touched}">
                <label for="formFields_1">Email Address</label>
                <input [formControl]="complexForm.controls['emailAddress']" type="text" spellcheck="false" id="formFields_1" placeholder="" size="35">
                <span *ngIf="complexForm.controls['emailAddress'].hasError('email') && complexForm.controls['emailAddress'].touched" class="tooltip-content">
                    Please enter a valid email address (ex. joan@vmware.com)
                </span>
          </div>   
          <div class="form-group" [ngClass]="{'has-error':!complexForm.controls['firstName'].valid && complexForm.controls['firstName'].touched}">
              <label for="formFields_2">First Name</label>
                <input [formControl]="complexForm.controls['firstName']" type="text" spellcheck="false" id="formFields_2" placeholder="" size="35">
                <span *ngIf="complexForm.controls['firstName'].hasError('required') && complexForm.controls['firstName'].touched" class="tooltip-content">
                    Your first name must contain at least one letter
                </span>
          </div>
     </section>
</form>

```

If I want to apply the class `form-error` to `<form>` if the forms error count is greater than 1, how do I do this? Thanks for your ideas.