1. 首先，创建包含嵌套FormArray的FormGroup。例如，我们创建一个如下所示的FormGroup：

this.form = this.fb.group({
  name: '',
  addresses: this.fb.array([])
})

2. 然后，我们可以使用FormBuilder来创建一个FormArray。例如，假设我们要添加两个地址，我们可以这样做：

this.addresses = this.form.get('addresses') as FormArray;
this.addresses.push(this.fb.group({
  street: '',
  city: '',
  state: '',
  zip: ''
}));
this.addresses.push(this.fb.group({
  street: '',
  city: '',
  state: '',
  zip: ''
}));

3. 现在，我们可以使用PatchValue更新FormGroup中的嵌套FormArray。例如，如果我们要更新第一个地址的街道和城市，我们可以这样做：

this.form.patchValue({
  addresses: [
    { street: '123 Main St', city: 'Anytown' },
    {}
  ]
});

注意，我们使用对象数组来更新地址，同时留空第二个对象以保持其原始值。如果我们不这样做，第二个地址将被删除。

完整示例代码如下：

import { Component, OnInit } from '@angular/core';
import { FormBuilder, FormGroup, FormArray } from '@angular/forms';

@Component({
  selector: 'app-address-form',
  templateUrl: './address-form.component.html',
  styleUrls: ['./address-form.component.css']
})
export class AddressFormComponent implements OnInit {
  form: FormGroup;
  addresses: FormArray;

  constructor(private fb: FormBuilder) { }

  ngOnInit() {
    this.form = this.fb.group({
      name: '',
      addresses: this.fb.array([])
    });

    this.addresses = this.form.get('addresses') as FormArray;
    this.addresses.push(this.fb.group({
      street: '',
      city: '',
      state: '',
      zip: ''
    }));
    this.addresses.push(this.fb.group({
      street: '',
      city: '',
      state: '',
      zip: ''
    }));
  }

  updateAddresses() {
    this.form.patchValue({
      addresses: [
        { street: '123 Main St', city: 'Anytown' },
        {}
      ]
    });
  }
}