angular - 如何在角度组件中使用 debounceTime？

Question

我的要求是以仅在用户停止键入后才显示错误消息的方式执行反应式表单字段验证。

我如何使用响应式表单和 Rxjs debounceTime 来实现这一点？

我正在寻找一种适用于反应式表单的解决方案

Answer 1

让它工作的（或至少一种）方法是在你去的时候动态地删除和添加你的验证器。

在您的输入中，使用keydown将在用户开始键入时剥离验证器的keyup绑定，以及将通过 debounceTime 管道运行然后重新应用验证器的绑定（但仅在指定的去抖动时间过去之后）。

代码在这里：

import { Component, OnInit } from '@angular/core';
import { FormBuilder, FormGroup, Validators } from '@angular/forms';
import { Subject } from 'rxjs';
import { debounceTime } from 'rxjs/operators';

@Component({
    selector: 'form-component',
    template: `
        <form [formGroup]="formGroup">
          <input type="text" formControlName="name" (keyup)="onKeyUp()" (keydown)="onKeyDown()" [ngClass]="{ 'invalid': formGroup.controls.name.invalid }">
        </form>
      `,
    styles: [
        '.invalid { border-color: red; color: red; }'
    ]
})
export class FormComponent implements OnInit {

    formGroup: FormGroup;
    subject: Subject<any> = new Subject();

    constructor(private formBuilder: FormBuilder) {}

    ngOnInit(): void {
        this.formGroup = this.formBuilder.group({
            name: [ '' ]
        });

        // Subscribe to the subject, which is triggered with each keyup
        // When the debounce time has passed, we add a validator and update the form control to check validity
        this.subject
            .pipe(debounceTime(500))
            .subscribe(() => {
                    this.formGroup.controls.name.setValidators([ Validators.minLength(5) ]);
                    this.formGroup.controls.name.updateValueAndValidity();
                }
            );
    }

    onKeyUp(): void {
        this.subject.next();
    }

    onKeyDown(): void {
        // When the user starts to type, remove the validator
        this.formGroup.controls.name.clearValidators();
    }

}

这里还有 StackBlitz：https ://stackblitz.com/edit/debounce-validator

Answer 2

debounceTime等待提到的时间段，然后调用 subscribe 方法。例如; debounceTime(1000)将等待 1 秒。它是通过pipes.

这可以添加到任何订阅方法。以下是工作示例

import { Component, OnInit } from '@angular/core';
import { Validators, AbstractControl } from '@angular/forms';
import { debounceTime } from 'rxjs/operators';

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


@Component({
    selector: 'app-customer-form',
    templateUrl: './customer-form.component.html',
})
export class CustomerFormComponent implements OnInit {

    emailMessage : string;

    private validationMessages = {
        required: "Email field is required",
        email: "Please enter a valid Email"
    }

    customerForm: FormGroup;

    customer = new Customer();

    constructor(private fb: FormBuilder) { }

    ngOnInit() {
        this.customerForm = this.fb.group({
            emailAddress: ['',
                [
                    Validators.required,
                    Validators.email
                ]
            ]
        })

        const emailControl = this.customerForm.get('emailAddress');
        emailControl.valueChanges.pipe( debounceTime(1000) ).subscribe(
            value => this.setEmailMessage(emailControl)
        )
    }

    setEmailMessage( c: AbstractControl ) : void {
        this.emailMessage = '';

        if ( (c.touched || c.dirty) && c.errors ) {
            this.emailMessage = Object.keys(c.errors).map( key => this.validationMessages[key]).join(' ');
        }

    }

}

在您的模板中

<input 
    class="form-control"
    id="emailId" type="email"
    placeholder="Email (required)"
    formControlName="emailAddress"
    [ngClass]="{ 'is-invalid': emailMessage }"/>
    <span class="invalid-feedback">
    {{ emailMessage }}
    </span>