angular学习之动态创建表单的方法

import { ReactiveFormsModule } from '@angular/forms';
@NgModule({
 imports: [
  ReactiveFormsModule
 ]
})

export class QuestionBase<T> {
  value: T;//表单元素的值
  key: string;//表单元素键的名称
  label: string;//输入元素的标题
  required: boolean;//是否必输
  order: number;//排序
  controlType: string;//表单的类型 选择框/文本输入框

  constructor(options: {
    value?: T,
    key?: string,
    label?: string,
    required?: boolean,
    order?: number,
    controlType?: string
  } = {}) {
    this.value = options.value;
    this.key = options.key || '';
    this.label = options.label || '';
    this.required = !!options.required;
    this.order = options.order === undefined ? 1 : options.order;
    this.controlType = options.controlType || '';
  }
}

import { QuestionBase } from './question-base';

export class QuestionDropdown extends QuestionBase<string>{
  controlType = "dropdown";
  options: { key: string, value: string }[] = [];

  constructor(options: {} = {}) {
    super(options);
    this.options = options["options"] || [];
  }
}

import { QuestionBase } from './question-base';

export class QuestionTextbox extends QuestionBase<string> {
  controlType = "textbox";
  type:string;
  constructor(options:{} ={}){
    super(options);
    this.type = options["type"]||""
  }
}

 getQuestions(){
  let questions:QuestionBase<any>[]=[
   new QuestionDropdown({
    key:'brave',
    label:'Bravery Rating',
    options:[
     {key:'solid',value:'Solid'},
     {key:'great',value:'Great'},
     {key:'good',value:'Good'},
     {key:'unproven',value:'Unproven'}
    ],
    order:3
   }),
   new QuestionTextbox({
    key:'firstName',
    label:'First name',
    value:"Bombasto",
    required:true,
    order:1
   }),
   new QuestionTextbox({
    key:'emailAddress',
    label:"Email",
    type:'email',
    order:2
   })
  ];
  return questions.sort((a, b) => a.order - b.order);
 }

 toFormGroup(questions: QuestionBase<any>[]) {
  let group: any = {};

  questions.forEach(question => {
   group[question.key] = question.required?new FormControl(question.value||"",Validators.required)
   :new FormControl(question.value||"");
  });
  return new FormGroup(group);
 }

<div [formGroup]="form">
 <label [attr.for]="question.key">{{question.label}}</label>
 <div [ngSwitch]="question.controlType">
  <input *ngSwitchCase="'textbox'" [formControlName]= "question.key" 
  [id]="question.key" [type]="question.type">
  <select [id]="question.key" *ngSwitchCase="'dropdown'"
   [formControlName]="question.key">
   <option *ngFor="let opt of question.options" [value]="opt.key">
    {{opt.value}}
   </option>
  </select>
 </div>
 <div class="errorMessage" *ngIf="!isValid">
  {{question.label}} is required
 </div>
</div>

import { Component, OnInit, Input } from '@angular/core';
import {FormGroup} from '@angular/forms';

import {QuestionBase} from '../question-base';

@Component({
 selector: 'app-dynamic-form-question',
 templateUrl: './dynamic-form-question.component.html',
 styleUrls: ['./dynamic-form-question.component.less']
})
export class DynamicFormQuestionComponent implements OnInit {
 @Input() question:QuestionBase<any>;
 @Input() form :FormGroup;
 get isValid(){
  return this.form.controls[this.question.key].valid;
 }
 constructor() { }

 ngOnInit() {
 }

}

  <div *ngFor="let question of questions" class="form-row">
   <app-dynamic-form-question [question]="question" [form]="form"></app-dynamic-form-question>
  </div>