<form id="login-form" class="login-from" #registerForm="ngForm" (ngSubmit)="doSubmit(registerForm.value)">
 <mat-form-field>
 <input matInput placeholder="邮箱" id="email" name="email" [(ngModel)]="formData.email" required pattern="[\w]+?@[\w]+?\.[a-z]+?">
 <mat-error *ngIf="formErrors.email">{{ formErrors.email }}</mat-error>
 </mat-form-field>

 <fieldset ngModelGroup="passwordGroup" #passwordGroup="ngModelGroup" aria-required="true">
 <mat-form-field>
 <input matInput placeholder="密码" type="password" id="password" name="password" [(ngModel)]="formData.password" #password="ngModel" required minlength="8">
 <!-- <mat-icon matSuffix (click)="hide = !hide">{{hide ? 'visibility' : 'visibility_off'}}</mat-icon> -->
 </mat-form-field>

 <mat-form-field>
 <!--使用自定义的校验器，加入repeatPassword指令，传入第一个密码输入框的ngModel,即用#password1="ngModel"声明的password1-->
 <input matInput placeholder="确认密码" type="password" id="passwordConfirm" name="passwordConfirm" [(ngModel)]="formData.passwordConfirm" [repeatPassword]="password" >
 <!-- <mat-icon matSuffix (click)="hide = !hide">{{hide ? 'visibility' : 'visibility_off'}}</mat-icon> -->
 <mat-error *ngIf="formErrors['passwordGroup.passwordConfirm']">{{ formErrors['passwordGroup.passwordConfirm'] }}</mat-error>
 </mat-form-field>
 </fieldset>

 <button class="w-100p" mat-raised-button [disabled] = "!registerForm.valid" >注册</button>
 </form>

组件

import { Component, OnInit ,ViewChild, AfterViewInit } from '@angular/core';import {NgForm} from "@angular/forms";import { Router } from '@angular/router';@Component({
 selector: 'app-register',
 templateUrl: './register.component.html',
 styleUrls: ['./register.component.css']
})
export class RegisterComponent implements OnInit {

 ngAfterViewInit(): void { //订阅表单值改变事件
 this.registerForm.valueChanges.subscribe(data => this.onValueChanged(data));
 } //找到表单
 @ViewChild('registerForm') registerForm: NgForm;

 formData = {} as any;

 doSubmit(obj: any) { //表单提交
 console.log(JSON.stringify(obj));
 }

 onValueChanged(data) { 
 for (const field in this.formErrors) { 
 this.formErrors[field] = ''; //取到表单字段
 const control = this.registerForm.form.get(field); //表单字段已修改或无效
 if (control && control.dirty && !control.valid) { //取出对应字段可能的错误信息
 const messages = this.validationMessages[field]; //从errors里取出错误类型，再拼上该错误对应的信息
 for (const key in control.errors) { this.formErrors[field] += messages[key] + '';
 }
 }

 }

 } //存储错误信息
 formErrors = { 'email': '', 'passwordGroup.password':'', 'passwordGroup.passwordConfirm':''
 }; //错误对应的提示
 validationMessages = { 'email': { 'required': '邮箱必须填写.', 'pattern': '邮箱格式不对',
 }, 'passwordGroup.password':{ 'required': '请输入密码', 'minlength': '密码太短',
 }, 'passwordGroup.passwordConfirm':{ 'required': '请重复输入密码', 'minlength': '密码太短', 'passwordNEQ':'两次输入密码不同', 'passwordInValid':''
 },

 };

 constructor(private router : Router) { }

 ngOnInit() {
 }

 gotoLogin(){ this.router.navigate(['user/login']);
 }

 recoverPwd(){ this.router.navigate(['/user/recover/pwd']);
 }
}

自定义校验器:repeat-password

import {Directive, Input, OnChanges, SimpleChanges} from '@angular/core';import {NG_VALIDATORS, FormControl, Validator, AbstractControl, ValidatorFn, NgModel} from "@angular/forms";@Directive({
 selector: '[repeatPassword]',
 providers: [{provide: NG_VALIDATORS, useExisting: RepeatPasswordDirective, multi: true}]
})
export class RepeatPasswordDirective implements Validator,OnChanges {

 /**
 * 校验方法
 * @param c
 * @returns {{[p: string]: any}}
 */
 validate(c: AbstractControl): {[p: string]: any} { 
 return verifyPassword(c,this.repeatPassword.control);
 }

 ngOnChanges(changes: SimpleChanges): void { 
 this.repeatPassword=changes['repeatPassword'].currentValue;
 } /**
 * 通过属性传入另一个input标签的model
 * 名称与选择器一致，就不需要在使用的时候加额外的属性传入
 */
 @Input() repeatPassword:NgModel;

 constructor() { }


}/**
 * 导出校验方法，供响应式表单使用
 * @param passwordController
 * @returns {(currentControl:AbstractControl)=>{[p: string]: any}}
 */export function repeatPassword(passwordController:FormControl):ValidatorFn { return (currentControl: AbstractControl): {[key: string]: any} => { return verifyPassword(currentControl,passwordController);
 };
}

function verifyPassword(currentControl: AbstractControl,passwordController:FormControl):{[key: string]: any} { if(!passwordController.valid) {
 console.log("密码1无效"); return {passwordInValid:{'errorMsg':''}}
 } if((!currentControl.untouched||currentControl.dirty)&&passwordController.value!=currentControl.value) { return {passwordNEQ:{'errorMsg':'两次密码输入不一致！'}}
 }
}

注意：

出现上图错误是因为创建指令时使用：ng g directive repeatPassword
命令，自动添加了前缀app

@Directive({ 
selector: '[appRepeatPassword]', 
providers: [{provide: NG_VALIDATORS, 
useExisting: RepeatPasswordDirective,
multi: true}]
})

改为repeatPassword即可

出现上图错误是由于

<input matInput placeholder="密码" type="password" id="password" name="password" [(ngModel)]="formData.password" #password1="ngModel" required minlength="8">
使用的字段是password，（不知道怎么描述）却是#password1。

改为#password即可