Question

我正在学习Ionic 3，并且在尝试创建一个检查唯一用户名的自定义验证程序时遇到此错误。我已尽力而为，但无法解决这个问题。

CustomValidators.ts

import { Directive, Input } from '@angular/core';

import { FormControl, Validator, AbstractControl } from '@angular/forms';
import { Http, Response, Headers, RequestOptions } from '@angular/http';
import {Observable} from 'rxjs/Rx';

export class CustomValidators {


    constructor(public http: Http){}

      public hasUniqueEmail(
        control: FormControl,
      ){

        return this.http.get('assets/users.json')
        .map(res => res.json())
        .catch((error:any) => Observable.throw(error.json().error || 'Server error'));

      }


}

signup.ts

import { Component } from '@angular/core';
import { IonicPage, NavController, NavParams } from 'ionic-angular';
import { FormBuilder, FormGroup,  Validators } from '@angular/forms';
import { CustomValidators } from '../../components/CustomValidators';

/**
 * Generated class for the SignupPage page.
 *
 * See http://ionicframework.com/docs/components/#navigation for more info
 * on Ionic pages and navigation.
 */


@IonicPage()

@Component({
  selector: 'page-signup',
  templateUrl: 'signup.html',
})


export class SignupPage {

  private sform : FormGroup;

  constructor(
        private formBuilder: FormBuilder,
        private myValidator: CustomValidators,
    ){

    this.sform = this.formBuilder.group({
      name: ['', Validators.compose([Validators.maxLength(30), Validators.pattern('[a-zA-Z ]*'), Validators.required])],
      email:  ['', Validators.compose([Validators.email,this.myValidator.hasUniqueEmail])],
      password: ['',Validators.required                                                                                             ],
    });

  }


  logForm() {

  }


}

这是我得到的错误：

"Uncaught (in promise): Error: No provider for CustomValidators!
Error
    at Error (native)
    at injectionError (http://localhost:8100/build/main.js:1583:86)
    at noProviderError (http://localhost:8100/build/main.js:1621:12)
    at ReflectiveInjector_._throwOrNull (http://localhost:8100/build/main.js:3122:19)
    at ReflectiveInjector_._getByKeyDefault (http://localhost:8100/build/main.js:3161:25)
    at ReflectiveInjector_._getByKey (http://localhost:8100/build/main.js:3093:25)
    at ReflectiveInjector_.get (http://localhost:8100/build/main.js:2962:21)
    at NgModuleInjector.get (http://localhost:8100/build/main.js:3909:52)
    at resolveDep (http://localhost:8100/build/main.js:11369:45)
    at createClass (http://localhost:8100/build/main.js:11225:91)"

Answer 1

您需要将提供程序添加到NgModule，即providers下的module.ts，

providers: [
  CustomValidators 
]

Answer 2

从我所看到的你遗漏了两件事

1）没有该类的装饰者，您正在导入Directive但从未使用它

import { Directive } from '@angular/core';

@Directive({
  name: 'directive-name'
})
export class CustomValidators {
  //...
}

2）NgModule中没有导入

import { CustomValidators } from 'path/to/file';

@NgModule({
  //...
  providers: [
    CustomValidators
  ]
})

如何解决“错误：未捕获（承诺）：错误：没有提供”Ionic 3中的错误

2 个答案: