Angular 4.x 基于AbstractControl自定义表单验证

Angular 为我们提供了多种方式和 API,进行表单验证。接下来我们将介绍如何利用 AbstractControl 实现 FormGroup 的验证。文章中会涉及 FormGroupFormControlFormBuilder 的相关知识,因此建议不了解上述知识的读者,阅读本文前先阅读 Angular 4.x Reactive Forms 这篇文章。

Contents

  • What is a FormGroup

  • FormBuilder/FormGroup source code

  • AbstractControl

  • Custom validation properties

    • Custom validation Object hook

What is a FormGroup

我们先来看一下 Angular 4.x Reactive Forms 中,使用 FormBuilder 的示例:

signup-form.component.ts

import { Component, OnInit } from '@angular/core';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';
import { User } from './signup.interface';

@Component({...})
export class SignupFormComponent implements OnInit {
  user: FormGroup;
  constructor(private fb: FormBuilder) {}
           
  ngOnInit() {
    this.user = this.fb.group({
      name: ['', [Validators.required, Validators.minLength(2)]],
      account: this.fb.group({
        email: ['', Validators.required],
        confirm: ['', Validators.required]
      })
    });
  }

  onSubmit({ value, valid }: { value: User, valid: boolean }) {
    console.log(value, valid);
  }
}

上面示例中,我们通过 FormBuilder 对象提供的 group() 方法,方便的创建 FormGroupFormControl 对象。接下来我们来详细分析一下 FormBuilder 类。

FormBuilder/FormGroup source code

FormBuilder source code

// angular2/packages/forms/src/form_builder.ts 片段
@Injectable()
class FormBuilder {
  
  // 基于controlsConfig、extra信息,创建FormGroup对象
  group(controlsConfig: {[key: string]: any}, extra: 
      {[key: string]: any} = null): FormGroup {}
  
  // 基于formState、validator、asyncValidator创建FormControl对象
  control(
      formState: Object, validator: ValidatorFn|ValidatorFn[] = null,
      asyncValidator: AsyncValidatorFn|AsyncValidatorFn[] = null): FormControl {}
  
  //基于controlsConfig、validator、asyncValidator创建FormArray对象
  array(
      controlsConfig: any[], validator: ValidatorFn = null,
      asyncValidator: AsyncValidatorFn = null): FormArray {}
}

首先,我们先来看一下 group() 方法:

group(controlsConfig: {[key: string]: any}, extra: {[key: string]: any} = null): 
  FormGroup {}

group() 方法签名中,可以清楚的知道该方法的输入参数和返回类型。具体的使用示例如下:

this.user = this.fb.group({
     name: ['', [Validators.required, Validators.minLength(2)]],
     account: this.fb.group({
        email: ['', Validators.required],
        confirm: ['', Validators.required]
     })
});

接下来我们来看一下 group() 方法的内部实现:

 group(controlsConfig: {[key: string]: any}, extra: {[key: string]: any} = null):     
     FormGroup {
        // 创建controls对象集合
        const controls = this._reduceControls(controlsConfig); 
       // 获取同步验证器
        const validator: ValidatorFn = extra != null ? extra['validator'] : null;
        // 获取异步验证器
        const asyncValidator: AsyncValidatorFn = extra != null ?
          extra['asyncValidator'] : null;
    return new FormGroup(controls, validator, asyncValidator);
  }

我们在来看一下 _reduceControls() 方法的内部实现:

_reduceControls(controlsConfig: {[k: string]: any}): {[key: string]: AbstractControl} {
    const controls: {[key: string]: AbstractControl} = {};
    // controlsConfig - {name: [...], account: this.fb.group(...)}
    Object.keys(controlsConfig).forEach(controlName => {
      // 获取控件的名称,然后基于控件对应的配置信息,创建FormControl控件,并保存到controls对象上
      controls[controlName] = this._createControl(controlsConfig[controlName]);
    });
    return controls;
}

继续看一下 _createControl() 方法的内部实现:

_createControl(controlConfig: any): AbstractControl {
    if (controlConfig instanceof FormControl || controlConfig instanceof FormGroup ||
        controlConfig instanceof FormArray) {
      return controlConfig;
    } else if (Array.isArray(controlConfig)) {
      // controlConfig - ['', [Validators.required, Validators.minLength(2)]]
      const value = controlConfig[0]; // 获取初始值
      // 获取同步验证器
      const validator: ValidatorFn = controlConfig.length > 1 ? controlConfig[1] : null;
      // 获取异步验证器
      const asyncValidator: AsyncValidatorFn = controlConfig.length > 2 ? 
            controlConfig[2] : null;
      // 创建FormControl控件
      return this.control(value, validator, asyncValidator);
    } else {
      return this.control(controlConfig);
    }
  }

最后我们看一下 control() 方法的内部实现:

control(
      formState: Object, 
      validator: ValidatorFn|ValidatorFn[] = null,
      asyncValidator: AsyncValidatorFn|AsyncValidatorFn[] = null): FormControl {
    return new FormControl(formState, validator, asyncValidator);
}

现在先来总结一下,通过分析 FormBuilder 类的源码,我们发现:

this.fb.group({...}, { validator: someCustomValidator })

等价于

new FormGroup({...}, someCustomValidator)

在我们实现自定义验证规则前,我们在来介绍一下 FormGroup 类。

FormGroup source code

// angular2/packages/forms/src/model.ts  片段
export class FormGroup extends AbstractControl {
  constructor(
      public controls: {[key: string]: AbstractControl}, 
      validator: ValidatorFn = null,
      asyncValidator: AsyncValidatorFn = null) {
    super(validator, asyncValidator);
    this._initObservables();
    this._setUpControls();
    this.updateValueAndValidity({onlySelf: true, emitEvent: false});
  }
}  

通过源码我们发现,FormGroup 类继承于 AbstractControl 类。在创建 FormGroup 对象时,会把 validatorasyncValidator 作为参数,然后通过 super 关键字调用基类 AbstractControl 的构造函数。

AbstractControl

接下来我们来看一下 AbstractControl 类:

// angular2/packages/forms/src/model.ts 片段
export abstract class AbstractControl {
  _value: any;
  ...
  private _valueChanges: EventEmitter<any>;
  private _statusChanges: EventEmitter<any>;
  private _status: string;
  private _errors: ValidationErrors|null;
  private _pristine: boolean = true;
  private _touched: boolean = false;
 
  constructor(public validator: ValidatorFn, public asyncValidator: AsyncValidatorFn) {}
  // 获取控件的valid状态,用于表示控件是否通过验证    
  get valid(): boolean { return this._status === VALID; } 

  // 获取控件的invalid状态,用于表示控件是否通过验证
  get invalid(): boolean { return this._status === INVALID; } 

  // 获取控件的pristine状态,用于表示控件值未改变
  get pristine(): boolean { return this._pristine; } 

  // 获取控件的dirty状态,用于表示控件值已改变
  get dirty(): boolean { return !this.pristine; }

  // 获取控件的touched状态,用于表示控件已被访问过
  get touched(): boolean { return this._touched; } 
  ...
}

使用 AbstractControl 不是实现我们自定义 FormGroup 验证的关键,因为我们也可以注入 FormGroup 来实现与表单控件进行交互。现在我们再来观察一下最初的代码:

@Component({...})
export class SignupFormComponent implements OnInit {
  user: FormGroup;
  constructor(private fb: FormBuilder) {}
  ngOnInit() {
    this.user = this.fb.group({
      name: ['', [Validators.required, Validators.minLength(2)]],
      account: this.fb.group({
        email: ['', Validators.required],
        confirm: ['', Validators.required]
      })
    });
  }
}

接下来我们要实现的自定义验证规则是,确保 email 字段的值与 confirm 字段的值能够完全一致。我们可以通过 AbstractControl 来实现该功能,首先我们先来定义验证函数:

email-matcher.ts

export const emailMatcher = () => {};

下一步,我们需要注入 AbstractControl

export const emailMatcher = (control: AbstractControl): {[key: string]: boolean} => {
    
};

Angular 4.x Reactive Forms 文章中,我们介绍了通过 FormGroup 对象 (FormGroup 类继承于AbstractControl),提供的 get() 方法,可以获取指定的表单控件。get() 方法的签名如下:

get(path: Array<string|number>|string): AbstractControl { return _find(this, path, '.'); }

// 使用示例 - 获取sub-group的表单控件
this.form.get('person.name'); 
-OR-
this.form.get(['person', 'name']);

具体示例如下:

<div class="error" *ngIf="user.get('foo').touched && 
  user.get('foo').hasError('required')">
       This field is required
</div>

了解完 AbstractControl,接下来我们来更新一下 emailMatcher 函数:

export const emailMatcher = (control: AbstractControl): {[key: string]: boolean} => {
  const email = control.get('email');
  const confirm = control.get('confirm');
};

上面的示例中,control 表示的是 FormGroup 对象,emailconfirm 都是表示 FormControl 对象。我们可以在控制台中输出它们的值:

► FormGroup {asyncValidator: null, _pristine: true, _touched: false, _onDisabledChange: Array[0], controls: Object…}
► FormControl {asyncValidator: null, _pristine: true, _touched: false, _onDisabledChange: Array[1], _onChange: Array[1]…}
► FormControl {asyncValidator: null, _pristine: true, _touched: false, _onDisabledChange: Array[1], _onChange: Array[1]…}

Custom validation properties

实际上 emailMatcher 自定义验证规则,就是比较 emailconfirm 控件的值是否一致。如果它们的值是一致的,那么返回 null,表示验证通过,没有出现错误。具体代码如下:

export const emailMatcher = (control: AbstractControl): {[key: string]: boolean} => {
  const email = control.get('email');
  const confirm = control.get('confirm');
  if (!email || !confirm) return null;
  if (email.value === confirm.value) {
    return null;
  }
};

上述代码意味着如果一切正常,我们都不会返回任何错误。现在我们需要添加自定义验证。

Custom validation Object hook

我们先来看一下,在 HTML 模板中,我们自定义验证规则的预期使用方式:

...
  <div formGroupName="account">
    <label>
      <span>Email address</span>
      <input type="email" placeholder="Your email address" formControlName="email">
    </label>
    <label>
      <span>Confirm address</span>
      <input type="email" placeholder="Confirm your email address" 
           formControlName="confirm">
    </label>
    <div class="error" *ngIf="user.get('account').touched && 
        user.get('account').hasError('nomatch')">
        Email addresses must match
    </div>
  </div>
...

忽略掉其它无关的部分,我们只关心以下的代码片段:

user.get('account').hasError('nomatch')

这意味着,我们需要先获取 account 对象 (FormGroup实例),然后通过 hasError() 方法,判断是否存在 nomatch 的错误。接下来我们按照该需求更新 emailMatcher 函数,具体如下:

export const emailMatcher = (control: AbstractControl): {[key: string]: boolean} => {
  const email = control.get('email');
  const confirm = control.get('confirm');
  if (!email || !confirm) return null;
  return email.value === confirm.value ? null : { nomatch: true };
};

最后,我们需要导入我们的自定义验证规则,然后在调用 fb.group() 创建 account FormGroup对象时,设置第二个参数,具体示例如下:

...
import { emailMatcher } from './email-matcher';
...
  ngOnInit() {
    this.user = this.fb.group({
      name: ['', Validators.required],
      account: this.fb.group({
        email: ['', Validators.required],
        confirm: ['', Validators.required]
      }, { validator: emailMatcher })
    });
  }
...

完整的示例代码如下:

signup.interface.ts

export interface User {
  name: string;
  account: {
    email: string;
    confirm: string;
  }
}

email-matcher.ts

export const emailMatcher = (control: AbstractControl): {[key: string]: boolean} => {
  const email = control.get('email');
  const confirm = control.get('confirm');
  if (!email || !confirm) {
    return null;
  }
  return email.value === confirm.value ? null : { nomatch: true };
};

signup-form.component.ts

import { Component, OnInit } from '@angular/core';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';
import { emailMatcher } from './email-matcher';

@Component({
  selector: 'signup-form',
  template: `
    <form class="form" novalidate (ngSubmit)="onSubmit(user)" [formGroup]="user">
      <label>
        <span>Full name</span>
        <input type="text" placeholder="Your full name" formControlName="name">
      </label>
      <div class="error" *ngIf="user.get('name').touched && 
        user.get('name').hasError('required')">
        Name is required
      </div>
      <div formGroupName="account">
        <label>
          <span>Email address</span>
          <input type="email" placeholder="Your email address" formControlName="email">
        </label>
        <label>
          <span>Confirm address</span>
          <input type="email" placeholder="Confirm your email address" 
            formControlName="confirm">
        </label>
        <div class="error" *ngIf="user.get('account').touched && 
            user.get('account').hasError('nomatch')">
          Email addresses must match
        </div>
      </div>
      <button type="submit" [disabled]="user.invalid">Sign up</button>
    </form>
  `
})
export class SignupFormComponent implements OnInit {
  user: FormBuilder;
  constructor(public fb: FormBuilder) {}
  ngOnInit() {
    this.user = this.fb.group({
      name: ['', Validators.required],
      account: this.fb.group({
        email: ['', Validators.required],
        confirm: ['', Validators.required]
      }, { validator: emailMatcher })
    });
  }
  onSubmit({ value, valid }) {
    console.log(value, valid);
  }
}

具体详情,可以查看线上示例

参考资源

    原文作者:semlinker
    原文地址: https://segmentfault.com/a/1190000009045615
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
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