angular4 Form表单相关

逃离我推掉我的手 2022-05-08 12:04 54阅读 0赞

原文出处：[https://www.cnblogs.com/artimis/p/9019518.html][https_www.cnblogs.com_artimis_p_9019518.html]  （原文更易阅读）

ng4中，有两种方式去声明一个表单

*  一：Template-Driven Forms - 模板驱动式表单   \[引入FormsModule\]

**1.ngForm赋值 **\[可以方便的获取表单的**值**\]

<form #f='ngForm' novalidate (ngSumbit)='onSubmit(f)'>
      <input type='text'
             name='username'
             [(ngModel)]='login.username'
             required>
      <div *ngIf='f.controls.username?.required' class='error'>
        Name is required. 
     </div> 
    </form>

**2.ngModel绑定 **\[ngModel会自动关联表单控件name属性，并使用该值作为ngForm对象的属性名\]

以下有三种写法：

**3.ngModel赋值 **\[可以操纵表单控件的**事件**\]

<form #f='ngForm' novalidate (ngSumbit)='onSubmit(f)'>
      <input type='text'
              name='username'
              [(ngModel)]='login.username'
              #username='ngModel'
              (change)='changeName(username.value)'
              required>
      <div *ngIf='username.error?.required && username.touched' class='error'>
        Name is required. 
     </div> 
    </form>

**4.验证规则相关 **\[required/minlength/maxlength等\]

<form #f='ngForm' novalidate (ngSumbit)='onSubmit(f)'>
      <input  type='text'
    　　　　　  name='username'
    　　　　　  [(ngModel)]='login.username'　
    　         #username='ngModel'
               minlength='8'>
      <div *ngIf='username.error?.minlength && username.touched' class='error'>
        The minlength is 8.
     </div> 
    </form>

**5.验证状态相关 **\[touched/valid/invalid/pristine/dirty/untouched等\]

valid：控件有效

invalid：控件无效

pristine：控件值未改变

dirty：控件值已改变

untouched：表单控件未被访问过

<form novalidate #f='ngForm'>
        ...
       <button type='submit' 
               [disabled]='f.invalid' 
               (click)='onSubmit(f)'>
               submit
      </button>
    </form>

*  二：Reactive Forms (Model-Driven Forms) - 响应式表单  \[引入ReactiveFormsModule\]

**1.FormGroup（FormControl+FormArray）**\[表单对象\]

*   FormGroup*：**包含一组FormControl和FormArray的实例**，可用于跟踪一组实例的值和验证状态

*   FormControl & FormArray*：为单个表单控件提供支持的类，用于跟踪控件的值和验证状态 前者是单值类型，后者是多值类型

**2.Validators** \[表单验证\]

//html方面
    
    <form novalidate [formGroup]='thatForm'>
        <input type='text' formControlName='name'>
        <div class='error' 
               *ngIf="thatForm.get('name').hasError('required') && 
                      thatForm.get('name').touched">
                Name is required
        </div>
        <div class='error' 
               *ngIf="thatForm.get('name').hasError('minlength') && 
                      thatForm.get('name').touched">
                The minlength is 2.
        </div>
    </form>

//xx.component.ts
    
    export class xxComponent implements OnInit{
        thatForm: FormGroup;
        constructor(){};
       ngOnInit() {
        this.thatForm=new FormGroup({
           name:new FormGroup('',[Validators.required,Validators.minLength(2)])     
       })      
      }
    }

**3.FormBuilder** \[简化新建FormGroup对象整个过程\]

//FormGroup用法
    
    export class xxComponent implements OnInit{
        thatForm: FormGroup;
        constructor(){};
       ngOnInit() {
        this.thatForm=new FormGroup({
           name:new FormGroup('',[Validators.required,Validators.minLength(2)])     
       })      
      }
    }

//FormBuilder用法
    
    export class xxComponent implements OnInit{
        thatForm: FormGroup;
        constructor(private formBuilder: FormBuilder){};
       ngOnInit() {
          this.thatForm=this.formBuilder.group({
              name:['',[Validator.required,Validators.minLength(2)]]
         })
       }
    }

**4.FormValidation** \[统一管理验证错误\]

//html方面
    <form novalidate [formGroup]='thatForm'>
        <input type='text' formControlName='name'>
        <div class='error'>
          {
      {
      formValidation.msgs.name.errors}}
        </div>
    </form>

//form-validation.ts
    
    export class xxValidation extends FormValidation{
       constructor(){
         super()
      }
      msgs={
        name:{
          errors:'',
          messages:{ 
             required:'please type the name.',
             minlength:'please enter 3 charactors atleast.'
         }
       }
     }
    }

//xx.component.ts
    
    export class xxComponent implements OnInit{
        formValidation:xxValidation=new xxValidation();
         thatForm:FormGroup;
    
        constructor(private formBuilder: FormBuilder){}
         ngOnInit(){
          this.thatForm=this.formBuilder.group({
           name:['',[Validators.required,Validators.minLength(4)]] 
         })
       }
       
    }

*  **两种方式的比较：**

**模板驱动表单（Template-Driven Forms）**

1.使用方便

2.适用于简单的场景

3.通过\[(ngModel)\]实现数据双向绑定

4.最小化组件类的代码

5.不利于单元测试

**响应式表单（Reactive Forms）**

1.比较灵活

2.适用于复杂的场景

3.简化了HTML模板的代码，把验证逻辑抽离出来了

4.方便跟踪表单控件值的变化