表單欄位驗證validator

src/app/app.component.html

@@ -1,9 +1,15 @@
-<div [formGroup] = "form">
-  <div formArrayName="Tasks" *ngFor="let control of tasks.controls; let index = index">
-    <ng-container [formGroupName]="index">
-      <input type="text" placeholder="主旨" formControlName="Subject"/>
-      <input type="text" placeholder="內容" formControlName="Content"/>
+<div [formGroup]="form">
+  <div>
+    帳號：<input type="text" formControlName="id" />
+    <ng-container *ngIf="id.touched">
+      <span *ngIf="id.hasError('required')">帳號為必填欄位</span>
     </ng-container>
   </div>
+  <div>
+    密碼：<input type="password" formControlName="password" />
+  </div>
+  <div>
+    <button type="reset">重設</button>
+    <button type="submit">登入</button>
+  </div>
 </div>
-<pre>{{form.value| json}}</pre>

src/app/app.component.ts

@@ -1,28 +1,44 @@
 import { Component } from '@angular/core';
-import { FormArray, FormControl, FormGroup } from '@angular/forms';
-
+import {
+  FormBuilder,
+  FormControl,
+  FormGroup,
+  Validators,
+} from '@angular/forms';
 
 @Component({
   selector: 'my-app',
   templateUrl: './app.component.html',
   styleUrls: ['./app.component.css'],
 })
-export class AppComponent  {
-  readonly form = new FormGroup({
-    Tasks: new FormArray([]),
-  });
+export class AppComponent {
+  // 方法一
+  // readonly form = new FormGroup({
+  //   id: new FormControl('', [Validators.required]),
+  //   password: new FormControl(''),
+  // });
 
-  get tasks(): FormArray{
-    return this.form.get('Tasks') as FormArray;
-  }
+  // 方法二
+  // readonly form = new FormGroup({
+  //   id: new FormControl('', { validators: [Validators.required] }),
+  //   password: new FormControl(''),
+  // });
+
+  // 方法三
+  // readonly form = this.fb.group({
+  //   id: this.fb.control('', [Validators.required]),
+  //   password: this.fb.control('')
+  // });
+
+  // 方法四
+  readonly form = this.fb.group({
+    id: this.fb.control('', { validators: [Validators.required] }),
+    password: this.fb.control(''),
+  });
 
-  ngOnInit(): void{
-    this.tasks.push(//注意此push用法
-      new FormGroup({
-        Subject: new FormControl(),
-        Content: new FormControl(),
-      })
-    );
+  get id(): FormControl {
+    return this.form.get('id') as FormControl;
   }
 
+  constructor(private fb: FormBuilder) {}
 }