表單陣列結構的操作

預設數量只會根據原模型數量去設定
包含push method，可以加入新的Formgroup

src/app/app.component.html

@@ -1,11 +1,15 @@
-<div [formGroup]="form">
-  <div>工作事項:<input type="text" formControlName="subject" /></div>
-  <div>工作內容:<input type="text" formControlName="content" /></div>
-  <div>
-    <button type="button" (click) = "onReset()">Reset</button>
-    <button type="button" (click) = "onSetValue()">Set Value</button>
-    <button type="button" (click) = "onPatchValue()">Patch Value</button>
+<button type="button" (click)="onSetValue()">Set</button>
+<button type="button" (click)="onAdd()">Add</button>
+<button type="button" (click)="onClear()">Clear</button>
+<div class="form" [formGroup]="form">
+  <div formArrayName="tasks" *ngFor="let control of tasks.controls; let index = index">
+    <ng-container [formGroupName]="index">
+      <div>工作事項：<input type="text" formControlName="subject" /></div>
+      <div>工作內容：<input type="text" formControlName="content" /></div>
+      <button type="button" (click)="onRemove(index)">Remove</button>
+      <hr>
+    </ng-container>
   </div>
 </div>
-<pre>{{form.value |json}}</pre>
-<pre>{{form.dirty |json}}</pre>
+
+<pre>{{ tasks.value | json }}</pre>

src/app/app.component.ts

@@ -1,6 +1,7 @@
 import { Component, OnDestroy, OnInit } from '@angular/core';
 import {
   AbstractControl,
+  FormArray,
   FormBuilder,
   FormControl,
   ValidationErrors,
@@ -15,20 +16,34 @@ import { debounce, debounceTime, distinctUntilChanged, filter, map } from 'rxjs/
   styleUrls: ['./app.component.css'],
 })
 export class AppComponent {
-
-  constructor(private fb: FormBuilder) { }
-  readonly form = this.fb.group({
-    subject: this.fb.control(''),
-    content: this.fb.control(''),
+  form = this.fb.group({
+    tasks: this.fb.array([]),
   });
+  get tasks(): FormArray {
+    return this.form.get('tasks') as FormArray;
+  }
+  constructor(private fb: FormBuilder) { }
 
   onSetValue(): void {
-    this.form.setValue({ subject: 'Task A', content: '' });
+    this.tasks.patchValue([
+      { subject: 'Task A', content: 'Do something...' },
+      { subject: 'Task B', content: 'Do something...' },
+    ])
   }
-  onPatchValue(): void {
-    this.form.patchValue({subject:'Task A'});
+
+  onAdd(): void{
+    const group = this.fb.group({
+      subject: this.fb.control(''),
+       content: this.fb.control(''),
+    });
+    this.tasks.push(group);
+  }
+
+  onRemove(index: number): void {
+    this.tasks.removeAt(index);
   }
-  onReset():void{
-    this.form.reset({subject:'', content:''});
+
+  onClear(): void {
+    this.tasks.clear();
   }
 }