Javascript 如何解决Ionic 3中的“错误：未捕获（承诺）：错误：没有提供者”错误
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How to solve "Error: Uncaught (in promise): Error: No provider for" error in Ionic 3
提问by J Snow
I'm learning Ionic 3 and I'm getting this error when trying to make a custom validator which checks for a unique username. I've tried my best but couldn't solve this issue.
我正在学习 Ionic 3 并且在尝试制作一个检查唯一用户名的自定义验证器时遇到此错误。我已经尽力了，但无法解决这个问题。
CustomValidators.ts
自定义验证器.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
注册.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() {
}
}
This is the error that I'm getting:
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)"
回答by Sajeetharan
You need to add the provider to the NgModule, i.e module.ts under providers,
需要在NgModule中添加provider，即provider下的module.ts，
providers: [
CustomValidators
]
回答by Baruch
From what I can see you're missing 2 things
据我所知，你错过了两件事
1) no decorator for the class, you're importing Directivebut never using it
1）该类没有装饰器，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) there's no import in the NgModule
2) NgModule 中没有导入
import { CustomValidators } from 'path/to/file';
@NgModule({
//...
providers: [
CustomValidators
]
})
