Angular learning talks about two types of forms

This article will take you to understand the forms inangularand learn about the two types of forms: template-driven and model-driven. I hope it will be helpful to everyone!

In Angular, there are two types of forms, namelytemplate drivenandmodel driven. [Recommended related tutorials: "angular tutorial"]

1. Template driver

1.1 Overview

Thecontrol logicof the form is written in thecomponent template, which is suitable forsimpleform types.

1.2 Get started quickly

1), introduce the dependent module FormsModule

import { FormsModule } from "@angular/forms" @NgModule({ imports: [FormsModule], }) export class AppModule {}

2), convert the DOM form to ngForm

3), declare the form field as ngModel

  提交 

4), get the form field value

import { NgForm } from "@angular/forms" export class AppComponent { onSubmit(form: NgForm) { console.log(form.value) // {username: ''} } }

5), form grouping

 
  
 
  
 提交 

import { NgForm } from "@angular/forms" export class AppComponent { onSubmit(form: NgForm) { console.log(form.value) // {contact: {phone: ''}, user:{username: ''}} } }

1.3 Form validation

##required Required fields
• minlength Minimum field length
• maxlength Maximum field length
• pattern validation regular example: pattern="\d" matches a value

•   提交 

  export class AppComponent { onSubmit(form: NgForm) { // 查看表单整体是否验证通过 console.log(form.valid) } }

   提交

  
 
请填写用户名
 
不符合正则规则
 
 

input.ng-touched.ng-invalid { border: 2px solid red; }

2. Model driven

2.1 Overview

Written in thecomponent class, it has more control over the verification logic and is suitable forcomplexform types.In a model-driven form, the form field needs to be an instance of the

class. The instance object canverify the value in the form field, whether the value has been modified, etc.

A group of form fields constitutes the entire form. The entire form needs to be an instance of theFormGroup
class, which canoverallvalidate the form.

FormControl: a form item in the form group
FormGroup: form group, the form is at least A FormGroup
FormArray: used for complex forms, which can dynamically add form items or form groups. During form validation, if one item in the FormArray fails, the entire form fails.

2.2 Get started quickly1), introduce ReactiveFormsModule

import { ReactiveFormsModule } from "@angular/forms" @NgModule({ imports: [ReactiveFormsModule] }) export class AppModule {}

2), in the component Create a FormGroup form control object in the class

import { FormControl, FormGroup } from "@angular/forms" export class AppComponent { contactForm: FormGroup = new FormGroup({ name: new FormControl(), phone: new FormControl() }) }

3), associate the form in the component template

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4), get the form value

export class AppComponent { onSubmit() { console.log(this.contactForm.value) } }

5), and set the form default value

contactForm: FormGroup = new FormGroup({ name: new FormControl("默认值"), phone: new FormControl(15888888888) })

6), form grouping

contactForm: FormGroup = new FormGroup({ fullName: new FormGroup({ firstName: new FormControl(), lastName: new FormControl() }), phone: new FormControl() })

 
   
  提交 

onSubmit() { console.log(this.contactForm.value.name.username) console.log(this.contactForm.get(["name", "username"])?.value) }

2.3 FormArrayRequirement: Display a set of contact information on the page by default , you can add more contact groups by clicking the button.

import { Component, OnInit } from "@angular/core" import { FormArray, FormControl, FormGroup } from "@angular/forms" @Component({ selector: "app-root", templateUrl: "./app.component.html", styles: [] }) export class AppComponent implements OnInit { // 表单 contactForm: FormGroup = new FormGroup({ contacts: new FormArray([]) }) get contacts() { return this.contactForm.get("contacts") as FormArray } // 添加联系方式 addContact() { // 联系方式 const myContact: FormGroup = new FormGroup({ name: new FormControl(), address: new FormControl(), phone: new FormControl() }) // 向联系方式数组中添加联系方式 this.contacts.push(myContact) } // 删除联系方式 removeContact(i: number) { this.contacts.removeAt(i) } ngOnInit() { // 添加默认的联系方式 this.addContact() } onSubmit() { console.log(this.contactForm.value) } }

 
 
    删除联系方式 
 
 添加联系方式 提交 

2.4 Built-in form validator1), use the validation rules provided by the built-in validator to validate the form fields

import { FormControl, FormGroup, Validators } from "@angular/forms" contactForm: FormGroup = new FormGroup({ name: new FormControl("默认值", [ Validators.required, Validators.minLength(2) ]) })

2), Get whether the entire form has passed the verification

onSubmit() { console.log(this.contactForm.valid) }

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3), and display the error message when the verification has passed in the component template

get name() { return this.contactForm.get("name")! }

  
 
请填写姓名
 
 姓名长度不能大于 {{ name.errors.maxlength.requiredLength }} 实际填写长度为 {{ name.errors.maxlength.actualLength }} 
 
 

2.5 Customize the synchronization form Validator

The type of custom validator is TypeScript class
The class contains specific verification methods, verification The method must be a static method
The verification method has a parameter control, of type AbstractControl. In fact, it is the type of the instance object of the FormControl class.
If the verification is successful, null will be returned.
If the verification fails, the object and the properties in the object will be returned. It is the verification identifier, and the value is true, indicating that the verification failed.
The return value of the verification method is ValidationErrors | null

• import { AbstractControl, ValidationErrors } from "@angular/forms" export class NameValidators { // 字段值中不能包含空格 static cannotContainSpace(control: AbstractControl): ValidationErrors | null { // 验证未通过 if (/\s/.test(control.value)) return { cannotContainSpace: true } // 验证通过 return null } }

  import { NameValidators } from "./Name.validators" contactForm: FormGroup = new FormGroup({ name: new FormControl("", [ Validators.required, NameValidators.cannotContainSpace ]) })

   
  姓名中不能包含空格
   

2.6 Custom asynchronous form validator

import { AbstractControl, ValidationErrors } from "@angular/forms" import { Observable } from "rxjs" export class NameValidators { static shouldBeUnique(control: AbstractControl): Promise { return new Promise(resolve => { if (control.value == "admin") { resolve({ shouldBeUnique: true }) } else { resolve(null) } }) } }

contactForm: FormGroup = new FormGroup({ name: new FormControl( "", [ Validators.required ], NameValidators.shouldBeUnique ) })

 
用户名重复
 
 
正在检测姓名是否重复

2.7 FormBuilderCreate the form

this.fb.control
• : Form item

this.fb.group
• : Form group, the form is at least one FormGroup

this.fb.array
• : used for complex forms, you can dynamically add form items or form groups during form validation , one item in FormArray failed, and the whole failed.

  import { FormBuilder, FormGroup, Validators } from "@angular/forms" export class AppComponent { contactForm: FormGroup constructor(private fb: FormBuilder) { this.contactForm = this.fb.group({ fullName: this.fb.group({ firstName: ["", [Validators.required]], lastName: [""] }), phone: [] }) } }

实际工作中，我们常常需要根据某个表单值得变化而进行相应的处理，一般可以使用ngModalChange或者表单来实现

import { FormControl, FormGroup } from "@angular/forms" export class AppComponent { public name = 'a'; public nameChange() { } }

import { FormControl, FormGroup } from "@angular/forms" export class AppComponent { contactForm: FormGroup = new FormGroup({ name: new FormControl() }) ngOnInt() { this.contactForm.get("name").valueChanges.subscribe(data => { console.log(data); } } }

   {{ item.name }}  提交 

import { Component } from "@angular/core" import { FormArray, FormBuilder, FormGroup } from "@angular/forms" interface Data { name: string value: string } @Component({ selector: "app-checkbox", templateUrl: "./checkbox.component.html", styles: [] }) export class CheckboxComponent { Data: Array = [ { name: "Pear", value: "pear" }, { name: "Plum", value: "plum" }, { name: "Kiwi", value: "kiwi" }, { name: "Apple", value: "apple" }, { name: "Lime", value: "lime" } ] form: FormGroup constructor(private fb: FormBuilder) { this.form = this.fb.group({ checkArray: this.fb.array([]) }) } onChange(event: Event) { const target = event.target as HTMLInputElement const checked = target.checked const value = target.value const checkArray = this.form.get("checkArray") as FormArray if (checked) { checkArray.push(this.fb.control(value)) } else { const index = checkArray.controls.findIndex( control => control.value === value ) checkArray.removeAt(index) } } onSubmit() { console.log(this.form.value) } }

export class AppComponent { form: FormGroup constructor(public fb: FormBuilder) { this.form = this.fb.group({ gender: "" }) } onSubmit() { console.log(this.form.value) } }

  Male  Female Submit 

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