formbuilder angular 8 on edit code example

Example: formbuilder angular example

this.contactForm = this.formBuilder.group({
  firstname: ['', [Validators.required, Validators.minLength(10)]],
  lastname: ['', [Validators.required, Validators.maxLength(15), Validators.pattern("^[a-zA-Z]+$")]],
  email: ['', [Validators.required, Validators.email]],
  gender: ['', [Validators.required]],
  isMarried: ['', [Validators.required]],
  country: ['', [Validators.required]],
  address: this.formBuilder.group({
    city: ['', [Validators.required]],
    street: ['', [Validators.required]],
    pincode: ['', [Validators.required]],
  })
});