angular预置验证器

angular在Validators类中预置了部分验证器。
可以通过如下代码导入

import { FormGroup, FormControl, FormBuilder, Validators } from '@angular/forms';

比如，我们使用一下必填验证required。
首先看下ts代码，在ts文件中，我们通过注入FormBuilder,创建一个FormGroup,在FormGroup中添加一个名称为sku的FormControl，然后我们校验sku，要求用户必须输入。

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

@Component({
  selector: 'app-demo-form-sku-form-builder',
  templateUrl: './demo-form-sku-form-builder.component.html',
  styleUrls: ['./demo-form-sku-form-builder.component.css']
})
export class DemoFormSkuFormBuilderComponent implements OnInit {

  myForm: FormGroup

  constructor(formBuilder: FormBuilder) {

    this.myForm = formBuilder.group({})
    let formControl: FormControl = new FormControl("", Validators.required)
    this.myForm.addControl("sku", formControl)
  }

  ngOnInit(): void {
  }

  onSubmit(form: any): void {
    console.log(form)
  }

}

html代码如下

<nz-card style="width:300px;">
    <form [formGroup]="myForm" nz-form (ngSubmit)="onSubmit(myForm.value)">
        <nz-form-item>
            <nz-form-label [nzSpan]="6" nzFor="sku">sku</nz-form-label>
            <nz-form-control [nzSpan]="14">
                <input nz-input name="sku" type="text" id="sku" [formControl]="myForm.controls['sku']">
                <nz-tag *ngIf="!myForm.controls['sku'].valid && myForm.controls['sku'].touched" [nzColor]="'magenta'">请输入SKU</nz-tag>
            </nz-form-control>
        </nz-form-item>
        <nz-form-item>
            <button type="submit" nz-button class="primary">Submit</button>
        </nz-form-item>
    </form>
</nz-card>

myForm.controls['sku'].valid用于校验用户是否输出，myForm.controls['sku'].touched判断用户是否点击了控件。如果用户点击控件后，没有输入内容。

自定义验证器

自定义验证器其实就是一个方法，这个方法有如下特点：

1. 接收一个FormControl作为参数

2. 验证失败时，返回一个StringMap<string,boolean>对象，键是错误代码、值是true
   ts文件如下

   import { Component, OnInit } from '@angular/core';
   import { FormGroup, FormControl, FormBuilder, Validators } from '@angular/forms';
   
   @Component({
     selector: 'app-demo-form-sku-form-builder',
     templateUrl: './demo-form-sku-form-builder.component.html',
     styleUrls: ['./demo-form-sku-form-builder.component.css']
   })
   export class DemoFormSkuFormBuilderComponent implements OnInit {
   
     myForm: FormGroup
   
     constructor(formBuilder: FormBuilder) {
   
    this.myForm = formBuilder.group({})
    let formControl: FormControl = new FormControl("", Validators.compose(
      [Validators.required, this.skuValidator]
    ))
    this.myForm.addControl("sku", formControl)
     }
   
     ngOnInit(): void {
     }
   
     onSubmit(form: any): void {
    console.log(form)
     }
   
     skuValidator(formControl: FormControl): { [s: string]: boolean } {
    if (!formControl.value.match(/^123/)) {
      return { invalidSku: true }
    }
    return { invalidSku: false }
     }
   
   }

   html代码如下

   <nz-card style="width:300px;">
    <form [formGroup]="myForm" nz-form (ngSubmit)="onSubmit(myForm.value)">
        <nz-form-item>
            <nz-form-label [nzSpan]="6" nzFor="sku">sku</nz-form-label>
            <nz-form-control [nzSpan]="14">
                <input nz-input name="sku" type="text" id="sku" [formControl]="myForm.controls['sku']">
                <nz-tag *ngIf="myForm.controls['sku'].hasError('required') && myForm.controls['sku'].touched" [nzColor]="'magenta'">请输入SKU</nz-tag>
                <nz-tag nzColor="error" *ngIf="myForm.controls['sku'].hasError('invalidSku')">
                    <i nz-icon nzType="close-circle"></i>
                    <span>error</span>
                  </nz-tag>
            </nz-form-control>
        </nz-form-item>
        <nz-form-item>
            <button type="submit" nz-button class="primary">Submit</button>
        </nz-form-item>
    </form>
   </nz-card>

   如果我们输入的sku不是123开头，可以看到以下页面