Angular 2 多个验证器

Question

一个表单域可以有多个验证器吗？我试过这个，但它导致了一些奇怪的错误（字段永远无效，即使满足要求）

this.username = new Control('', Validators.minLength(5), Validators.required);

如何使用多个验证器？

Answer 1

您可以使用 Validators.compose() 组合验证器

this.username = new Control('', 
    Validators.compose(
        [Validators.minLength(5), Validators.required]));

供异步验证器使用

this.username = new Control('', null,
    Validators.composeAsync(
        [someAsyncValidator, otherAsyncValidator]));

异步验证器存在一些未解决的问题，尤其是同步验证器与异步验证器结合时不起作用

• https://github.com/angular/angular/issues/8923
• https://github.com/angular/angular/issues/1068

要使同步验证器与异步验证器一起工作，请将同步验证器包装在 Promise 中并将它们组合为异步验证器，例如

this.username = new Control('', null,
    Validators.composeAsync([
        (control:Control) => Promise.resolve(Validators.minLength(5)(control)), 
        (control:Control) => Promise.resolve(Validators.required(control)),
        someAsyncValidator, otherAsyncValidator
    ]));

Answer 2

这个问题已经解决了

你可以创建一个验证器数组

this.username = new FormControl('', [ Validators.minLength(5), Validators.required ]); 

Answer 3

我建议使用 Validators.compose() 方法来组合所有非异步验证器，并为任何异步调用单独传入 Validators.composeAsync()。

FormControl 的构造函数参数如下：

1. formState（或简单的初始值）
2. 验证器（我建议在此处使用 Validators.compose([...])）
3. asyncValidators（我建议在此处使用 Validators.composeAsync([...])）

使用 FormBuilder 的示例（随意直接使用 Control）：

this.acctForm = this.fb.group({
            'name': [
                '',
                Validators.compose([
                    Validators.required, Validators.minLength(2), Validators.maxLength(20), Validators.pattern('[a-zA-Z]')
                ])
            ],
            'cellNumber': [
                '',
                Validators.compose([
                    Validators.required, Validators.pattern('[0-9]{10}')
                ]),
                Validators.composeAsync([
                    this.checkPhoneValid.bind(this)
                ])
            ]
        });

这有助于避免异步验证，直到非异步验证器有效（不包括初始检查，它很容易处理，请参见下文）。

一切组合示例（验证器、异步验证器和去抖动）：

import { Component, Injectable, OnInit } from '@angular/core';
import { Http } from '@angular/http';
import { FormBuilder, FormGroup, Validators, AbstractControl } from '@angular/forms';


@Component({
    selector: 'app-sandbox',
    templateUrl: './sandbox.component.html',
    providers: []
})
export class FormControlsDemoComponent implements OnInit {
    private debouncedTimeout;
    public acctForm: FormGroup;

    constructor(private http: Http, private fb: FormBuilder) {
        // @note Http should never be directly injected into a component, for simplified demo sake...
    }

    ngOnInit() {
        this.acctForm = this.fb.group({
            // Simple Example with Multiple Validators (non-async)
            'name': [
                '',
                Validators.compose([
                    Validators.required, Validators.minLength(2), Validators.maxLength(20), Validators.pattern('[a-zA-Z]')
                ])
            ],
            // Example which utilizes both Standard Validators with an Async Validator
            'cellNumber': [
                '',
                Validators.compose([
                    Validators.required, Validators.minLength(4), Validators.maxLength(15), Validators.pattern('[0-9]{10}')
                ]),
                Validators.composeAsync([
                    this.checkPhoneValid.bind(this) // Important to bind 'this' (otherwise local member context is lost)
                    /*
                        @note if using a service method, it would look something like this...
                        @example:
                            this.myValidatorService.phoneUniq.bind(this.myValidatorService)
                    */
                ])
            ],
            // Example with both, but Async is implicitly Debounced
            'userName': [
                '',
                Validators.compose([
                    Validators.required, Validators.minLength(4), Validators.maxLength(15), Validators.pattern('[a-zA-Z0-9_-]')
                ]),
                Validators.composeAsync([
                    this.checkUserUniq.bind(this) // @see above async validator notes regarding use of bind
                ])
            ]
        });

    }

    /**
     * Demo AsyncValidator Method
     * @note - This should be in a service
     */
    private checkPhoneValid(control: AbstractControl): Promise<any> {
        // Avoids initial check against an empty string
        if (!control.value.length) {
            Promise.resolve(null);
        }

        const q = new Promise((resolve, reject) => {
            // determine result from an http response or something...
            let result = true;

            if (result) {
                resolve(null);
            } else {
                resolve({'phoneValidCheck': false});
            }
        });
        return q;
    }

    /**
     * Demo AsyncValidator Method (Debounced)
     * @note - This should be in a service
     */
    private checkUserUniq(control: AbstractControl): Promise<any> {
        // Avoids initial check against an empty string
        if (!control.value.length) {
            Promise.resolve(null);
        }

        clearTimeout(this.debouncedTimeout);

        const q = new Promise((resolve, reject) => {

            this.debouncedTimeout = setTimeout(() => {

                const req = this.http
                    .post('/some/endpoint', { check: control.value })
                    .map(res => {
                        // some handler logic...
                        return res;
                    });

                req.subscribe(isUniq => {
                    if (isUniq) {
                        resolve(null);
                    } else {
                        resolve({'usernameUnique': false });
                    }
                });

            }, 300);
        });
        return q;
    }

}

有些人喜欢通过绑定到控件的 Observable valueChanges 来破解 debounced async 验证器，如下所示：

this.someControl.debounceTime(300).subscribe(val => {
      // async call...
});

我个人不建议在大多数情况下这样做，因为它会增加不必要的复杂性。

注意：从最新版本的 Angular（2 和 4）开始，这应该可以工作，因为 写这篇文章。