1. FormGroup和FormControl

FormGroup用来创建一个表单分组，FormControl则是表单分组中的每个表单元素。

示例代码：

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

@Component({
  selector: 'app-my-form',
  template: `
    

      
      
      Submit
    
  `
})
export class MyFormComponent implements OnInit {

  myForm: FormGroup;

  ngOnInit() {
    this.myForm = new FormGroup({
      username: new FormControl(''),
      password: new FormControl('')
    });
  }

  onSubmit() {
    console.log(this.myForm.value);
  }

}

2. FormArray

FormArray用来创建多个表单元素的数组，例如多选框和多个文本输入框。

示例代码：

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

@Component({
  selector: 'app-my-form',
  template: `
    

      

         Reading
         Dancing
         Singing
      
      Submit
    
  `
})
export class MyFormComponent implements OnInit {

  myForm: FormGroup;

  ngOnInit() {
    this.myForm = new FormGroup({
      hobbies: new FormArray([])
    });
    this.addCheckboxes();
  }

  private addCheckboxes() {
    const checkboxes = ['Reading', 'Dancing', 'Singing'];
    checkboxes.forEach((o, i) => {