Angular docs-表单-使用 reactive forms 创建动态表单

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使用 reactive forms 创建动态表单

使用 formGroup 动态呈现不能控件和验证器的表单。

Bootstrap

在 AppModule 中加载 ReactiveFormsModule:

//app.module.ts
import { BrowserModule }                from '@angular/platform-browser';
import { ReactiveFormsModule }          from '@angular/forms';
import { NgModule }                     from '@angular/core';

import { AppComponent }                 from './app.component';
import { DynamicFormComponent }         from './dynamic-form.component';
import { DynamicFormQuestionComponent } from './dynamic-form-question.component';

@NgModule({
  imports: [ BrowserModule, ReactiveFormsModule ],
  declarations: [ AppComponent, DynamicFormComponent, DynamicFormQuestionComponent ],
  bootstrap: [ AppComponent ]
})
export class AppModule {
  constructor() {
  }
}


//main.ts
import { platformBrowserDynamic } from '@angular/platform-browser-dynamic';
import { AppModule } from './app/app.module';

platformBrowserDynamic().bootstrapModule(AppModule);

Question 数据模型

每个动态呈现的表单都表示一个问题。先创建基本的类 QuestionBase：

//src/app/question-base.ts
export class QuestionBase<T>{
  value: T;
  key: string;
  label: string;
  required: boolean;
  order: number;
  controlType: string;

  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 || '';
  }
}

再创建呈现文件框问题的子类 TextboxQuestion 和呈现下拉选择框的问题子类 DropdownQuestion。

TextboxQuestion 中能基于 type 属性支持 text, email, url 等类型：

//src/app/question-textbox.ts
import { QuestionBase } from './question-base';

export class TextboxQuestion extends QuestionBase<string> {
  controlType = 'textbox';
  type: string;

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

//src/app/question-dropdown.ts
import { QuestionBase } from './question-base';

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

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

创建 QuestionControlService 将各问题数据模型转换返回 FormGroup：

//src/app/question-control.service.ts
import { Injectable }   from '@angular/core';
import { FormControl, FormGroup, Validators } from '@angular/forms';

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

@Injectable()
export class QuestionControlService {
  constructor() { }

  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);
  }
}

Question 表单组件

DynamicFormComponent 是入口及表单的主容器：

//dynamic-form.component.ts
import { Component, Input, OnInit }  from '@angular/core';
import { FormGroup }                 from '@angular/forms';

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

@Component({
  selector: 'dynamic-form',
  templateUrl: './dynamic-form.component.html',
  providers: [ QuestionControlService ]
})
export class DynamicFormComponent implements OnInit {

  @Input() questions: QuestionBase<any>[] = [];
  form: FormGroup;
  payLoad = '';

  constructor(private qcs: QuestionControlService) {  }

  ngOnInit() {
    this.form = this.qcs.toFormGroup(this.questions);
  }

  onSubmit() {
    this.payLoad = JSON.stringify(this.form.value);
  }
}

<!--dynamic-form.component.html-->
<div>
  <form (ngSubmit)="onSubmit()" [formGroup]="form">

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

    <div class="form-row">
      <button type="submit" [disabled]="!form.valid">Save</button>
    </div>
  </form>

  <div *ngIf="payLoad" class="form-row">
    <strong>Saved the following values</strong><br>
  </div>
</div>

DynamicFormQuestionComponent 基于绑定的 Question 内的数值，呈现具体的 Question：

//dynamic-form-question.component.ts
import { Component, Input } from '@angular/core';
import { FormGroup }        from '@angular/forms';

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

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

<!--dynamic-form-question.component.html-->
<div [formGroup]="form">
  <label [attr.for]="question.key"></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"></option>
    </select>

  </div> 

  <div class="errorMessage" *ngIf="!isValid"> is required</div>
</div>

获取问题集

//src/app/question.service.ts
import { Injectable }       from '@angular/core';

import { DropdownQuestion } from './question-dropdown';
import { QuestionBase }     from './question-base';
import { TextboxQuestion }  from './question-textbox';

@Injectable()
export class QuestionService {

  // Todo: get from a remote source of question metadata
  // Todo: make asynchronous
  getQuestions() {

    let questions: QuestionBase<any>[] = [

      new DropdownQuestion({
        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 TextboxQuestion({
        key: 'firstName',
        label: 'First name',
        value: 'Bombasto',
        required: true,
        order: 1
      }),

      new TextboxQuestion({
        key: 'emailAddress',
        label: 'Email',
        type: 'email',
        order: 2
      })
    ];

    return questions.sort((a, b) => a.order - b.order);
  }
}

在 AppComponent 中显示一个表单实例：

//app.component.ts
import { Component }       from '@angular/core';

import { QuestionService } from './question.service';

@Component({
  selector: 'my-app',
  template: `
    <div>
      <h2>Job Application for Heroes</h2>
      <dynamic-form [questions]="questions"></dynamic-form>
    </div>
  `,
  providers:  [QuestionService]
})
export class AppComponent {
  questions: any[];

  constructor(service: QuestionService) {
    this.questions = service.getQuestions();
  }
}

参考


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