表单的创建
1、Reactive forms
响应式表单，使用显式和不可变的方法来管理表单在给定时间点的状态，对表单状态的每个更改都返回一个新状态，该状态在更改之间维护模型的完整性。
几个关键词：FormControl/[formControl]; FormGroup/[formGroup]; [formControlName]; FormBuilder;

响应式的表单最主要的是form control

name = new FormControl('');//常用的参数有formState表示值，validators:[]表示验证new FormControl('abc',[Validators.required])<label> Name: <input type="text" [formControl]="name"></label><p> Value: {{ name.value }}</p>updateName() { this.name.setValue('Nancy');}getName(){ return this.name.value; //value 是 readonly}

当多个form control组合在一起的时候使用FormGroup

profileForm = new FormGroup({ firstName: new FormControl('',[Validators.required]), lastName: new FormControl(''), address:new FormGroup({ street: new FormControl('') })});//另外一种方式constructor(private fb: FormBuilder) { }profileForm = this.fb.group({ firstName: ['', Validators.required], lastName: [''],});<form [formGroup]="profileForm"> <label> First Name: <input type="text" formControlName="firstName"> </label> <label> Last Name: <input type="text" formControlName="lastName"> </label> <div formGroupName="address"> <h4>Address</h4> <label> Street: <input type="text" formControlName="street"> </label> </div></form>//获取form controlthis.profileForm.get('firstName');//批量更新this.profileForm.setValue(valueObj);//must all key existthis.profileForm.patchValue({ firstName: 'Nancy', address: { street: '123 Drew Street' }});

2、Template-driven forms
传统方式创建form，几个关键词：ngModel; ngForm
这种方式创建表单主要是通过model来实现双向绑定，通过ngForm来将普通的form转成angular form

<form #heroForm = "ngForm"> <div class="form-group"> <label>Name</label> <input type="text" class="form-control" name="name" [(ngModel)]="model.name" #name="ngModel"> </div> </form>

在这个例子中，heroForm有一个属性form，heroForm.form其实就和FormGroup创建的form一样了，
设置了#name="ngModel"，就可以用heroForm.controls.name来获取name了

表单的验证
整个表单的验证
Reactive form通过profileForm.invalid
Template-driven form通过heroForm.form.invalid

单个字段的验证
Reactive form直接获取即可

<form [formGroup] = "profileForm"> <input type="text" formControlName="lastName"> <div *ngIf="lastName.invalid && (lastName.dirty || lastName.touched)" class="alert alert-danger"> <div *ngIf="lastName.errors.maxlength"> Name must be at most 10 characters long. </div> </div></form>

如果formControlName是一个变量，用下面这种方式

<form [formGroup] = "profileForm"> <input type="text" [formControlName]="xxx"> <div *ngIf="profileForm.get('xxx').invalid && (profileForm.get('xxx').dirty || profileForm.get('xxx').touched)" class="alert alert-danger"> <div *ngIf="profileForm.get('xxx').errors.maxlength"> Name must be at most 10 characters long. </div> </div></form>

Template-driven通过变量判断

<input type="text" class="form-control" name="name" [(ngModel)]="model.name" required minlength="4" appForbiddenName="11111" #name="ngModel"><p *ngIf="name.invalid" class="alert alert-danger"> <span *ngIf="name.errors.required">Name is required</span> <span *ngIf="name.errors.minlength">Min 4 chars</span> <span *ngIf="name.errors.forbiddenName">This is forbidden name</span></p>

一定要有#name="ngModel"这句，这句是定义一个名称为name的form control

表单的提交
1、通过form的(ngSubmit)="onSubmit()"，怎么触发form的提交，和传统form是一样的
2、通过按钮的click事件

Reactive form<button click="onSubmit()" class="btn btn-success" [disabled]="profileForm.invalid">Submit</button>Template-driven form<button click="onSubmit()" class="btn btn-success" [disabled]="heroForm.form.invalid">Submit</button>