Angular8表单内置API窥探

创建

formControl

实例用于追踪单个表单控件的值和验证状态

<section>
  <div nz-row nzJustify="start" nzGutter="16">
    <div nz-col nzSpan="8">
      <input nz-input type="text" [formControl]="projectName" placeholder="请输入项目名称">
      <span *ngIf="!projectName.valid">missing required!</span>
    </div>
  </div>
</section>

import { Component, OnInit } from '@angular/core';
import { FormControl, Validators } from '@angular/forms';

@Component({
  selector: 'app-create-form',
  templateUrl: './create-form.component.html',
  styleUrls: ['./create-form.component.scss']
})
export class CreateFormComponent implements OnInit {
  projectName: FormControl;
  constructor() { }

  ngOnInit() {
    this.projectName = new FormControl('123');
  }
}

上述输入控件绑定了一个formControl类型的初始值，未添加任何校验规则，使用内置API添加规则、校验等操作。

  projectNameValidate() {
    // 清除已有的验证器
    this.projectName.clearValidators();
    // 添加新验证器
    this.projectName.setValidators([Validators.required]);
    this.projectName.updateValueAndValidity();
  }

 <div nz-col nzSpan="8">
      <button nz-button (click)="projectNameValidate()">验证</button>
    </div>

FormGroup

跟踪一组FormControl实例的值和有效性状态

<section>
  <form nz-form [formGroup]="outlayGroup" (ngSubmit)="outlayGroupSubmit($event)">
    <div nz-row nzGutter="8" nzJustify="start">
      <div nz-col nzFlex="flex" nzSpan="6">
        <nz-form-item>
          <nz-form-label nzSpan="8" nzRequired>团建</nz-form-label>
          <nz-form-control nzSpan="16">
            <input nz-input type="text" formControlName="activity">
          </nz-form-control>
        </nz-form-item>
      </div>
      <div nz-col nzFlex="flex" nzSpan="6">
        <nz-form-item>
          <nz-form-label nzSpan="8" nzRequired>项目调研</nz-form-label>
          <nz-form-control nzSpan="16">
            <input nz-input type="text" formControlName="project">
          </nz-form-control>
        </nz-form-item>
      </div>
    </div>
    <div nz-row>
      <div nz-col nzSpan="8">
        <button nz-button type="submit">提交申请</button>
      </div>
    </div>
  </form>
</section>

outlayFormInit() {
  this.outlayGroup = new FormGroup({
    activity: new FormControl(null, [Validators.required]),
    project: new FormControl(null, [Validators.required])
  });
}

目前表单是响应式类型，默认change状态进行校验，且初始值均为 空值（推荐使用null替代''）
现在需求有所变动，申请单默认团建费用初始值设为1001，但是公司今年效益不是很好，要求团建费用不得大于1000.

outlayFormInit() {
    this.outlayGroup = new FormGroup({
      activity: new FormControl(1001, [Validators.required, Validators.max(1000)]),
      project: new FormControl(null, [Validators.required])
    });
  }

如果我们进入申请页面，直接点击提交申请，虽然不会提交上去，但是也不会有提示或者报红效果，此刻需要我们进行手动校验表单内选项。

 outlayGroupSubmit(event) {
    if (!this.outlayGroup.valid) {
      const controls = this.outlayGroup.controls;
      for (const key in controls) {
        if (controls.hasOwnProperty(key)) {
          const formField = controls[key];
          formField.markAsDirty();
          formField.updateValueAndValidity();
        }
      }
      return;
    }
    // submit to ...
  }

如果要针对其中某个formControl进行操作，要先获取control再进行操作。

this.outlayGroup.get('activity').markAsDirty();
this.outlayGroup.get('activity').updateValueAndValidity();

tip：不要忘记标记为脏值！

FormArray

跟踪一个控件数组的值和有效性状态。

<section>
  <form nz-form [formGroup]="prosecuteForm" (ngSubmit)="prosecuteFormSubmit($event)">
    <div nz-row nzGutter="8" nzJustify="start">
      <div nz-col nzFlex="flex" nzSpan="6">
        <nz-form-item>
          <nz-form-label nzSpan="8" nzRequired>日期</nz-form-label>
          <nz-form-control nzSpan="16">
            <nz-date-picker formControlName="date"></nz-date-picker>
          </nz-form-control>
        </nz-form-item>
      </div>
      <div nz-col nzFlex="flex" nzSpan="6">
        <nz-form-item>
          <nz-form-label nzSpan="8" nzRequired>被告</nz-form-label>
          <nz-form-control nzSpan="16">
            <input nz-input type="text" formControlName="defendant">
          </nz-form-control>
        </nz-form-item>
      </div>
    </div>
    <div>
      <button nz-button (click)="addMembers()">继续添加</button>
      原告团体：
      <div formArrayName="plaintiff">
        <div nz-row nzGutter="8">
          <div nz-col nzSpan="6" *ngFor="let control of plaintiff.controls;let i = index;">
            <nz-form-item>
              <nz-form-control nzSpan="16">
                <input type="text" nz-input [formControlName]="i">
              </nz-form-control>
            </nz-form-item>
          </div>
        </div>
      </div>
    </div>
    <div nz-row>
      <div nz-col nzSpan="8">
        <button nz-button type="submit">提交申请</button>
      </div>
    </div>
  </form>
</section>

get plaintiff() {
    return this.prosecuteForm.get('plaintiff') as FormArray;
  }
  prosecuteFormInit() {
    this.prosecuteForm = new FormGroup({
      date: new FormControl(null, [Validators.required]),
      defendant: new FormControl(null, [Validators.required]),
      plaintiff: new FormArray([
        new FormControl(2, [Validators.required])
      ])
    });
  }
  addMembers() {
    this.plaintiff.push(new FormControl(null,[Validators.required]));
  }
  prosecuteFormSubmit() {
    console.log(this.prosecuteForm);
    this.plaintiff.controls.forEach((control, index) => {
      control.markAsDirty();
      control.updateValueAndValidity();
    });
  }

FormArray 的数组元素为 FormControl实例；从一组List内获取指定Control 可以通过at(index)获取后进行各种操作，这个很重要；添加新的Control需要获取到FromArray实例后push 而不是add方法。

FormBuilder

这是个可注入的服务提供者，用于创建响应式表单控件。

创建一个记录公司信息的简单表单

<section>
  <form nz-form [formGroup]="enterprisesFormData">
    <div nz-row nzGutter="8">
      <div nz-col nzSpan="8">
        <nz-form-item>
          <nz-form-label nzSpan="6">企业名称</nz-form-label>
          <nz-form-control nzSpan="18">
            <input type="text" nz-input formControlName="enterpriseName">
          </nz-form-control>
        </nz-form-item>
      </div>
      <div nz-col nzSpan="8">
        <nz-form-item>
          <nz-form-label nzSpan="6">企业地址</nz-form-label>
          <nz-form-control nzSpan="18">
            <input type="text" nz-input formControlName="enterpriseAddr">
          </nz-form-control>
        </nz-form-item>
      </div>
      <div nz-col nzSpan="8">
        <nz-form-item>
          <nz-form-label nzSpan="6">企业电话</nz-form-label>
          <nz-form-control nzSpan="18">
            <input type="text" nz-input formControlName="tel">
          </nz-form-control>
        </nz-form-item>
      </div>
    </div>
  </form>
</section>

enterprisesInit() {
    this.enterprisesFormData = this.fb.group({
      enterpriseName: ['', Validators.required],
      enterpriseAddr: [''],
      tel: ['']
    });
  }

使用这个服务创建表单比前面的三种方式都更加简单、明了。

更新（值、状态、添加、删除等）

FormControl

this.projectName.setValue('456');
this.projectName.patchValue('789');

this.projectName.setValidators([Validators.required, Validators.minLength(5)]);
this.projectName.markAsDirty();
this.projectName.updateValueAndValidity();

formControl就是一个控件了，无法添加和删除

FormGroup

outlayFormInit() {
    this.outlayGroup = new FormGroup({
      activity: new FormControl(1001, [Validators.required, Validators.max(1000)]),
      project: new FormControl(null, [Validators.required])
    });
    // 更新单个值
    this.outlayGroup.get('activity').setValue(2000);
    // 多个更新
    this.outlayGroup.patchValue({
      project: '11100001',
      activity: 0
    });
    // 添加
    this.outlayGroup.addControl('other', new FormControl(100,[Validators.max(99)]));
    this.outlayGroup.addControl('game', new FormControl(1000));
    // 移除
    this.outlayGroup.removeControl('game');
    // 状态
    this.outlayGroup.get('other').markAsDirty();
    this.outlayGroup.get('other').updateValueAndValidity();
  }

FormArray

get plaintiff() {
    return this.prosecuteForm.get('plaintiff') as FormArray;
  }
  addMembers() {
    this.plaintiff.push(new FormControl(null, [Validators.required]));
  }

添加使用 this.plaintiff.push(new FormControl())；
获取使用 this.plaintiff.at(i);
移除使用 this.plaintiff.removeAt(i)
更新具体 Control控件和校验 与 前面的API一致；

FormBuilder

这玩意可以创建任意类型控件，根据创建表单类型去使用对应的API；如果创建的是group类型，则与 FormGroup 一样使用。

校验

单个FormControl

直接使用

control.markAsDirty();
control.updateValueAndValidity();

整个form校验

就是将整个表单进行挨个校验的过程，一般为表单的controls属性值进行迭代校验，动态表单可能需要迭代嵌套的逻辑。

outlayGroupSubmit(event) {
    if (!this.outlayGroup.valid) {
      const controls = this.outlayGroup.controls;
      for (const key in controls) {
        if (controls.hasOwnProperty(key)) {
          const formField = controls[key];
          formField.markAsDirty();
          formField.updateValueAndValidity();
        }
      }
      return;
    }
    // submit to ...
  }