Validation Error Message not getting displayed for custom validation in Angular 2 - validation

Question

I have a register form where user need to provide username. When customer enters username, I want to show validation error message if that username already exists in db or not.
register.html
<-- code here-->
<div class="form-group">
<label for="username" class="col-sm-3 control-label">UserName</label>
<div class=" col-sm-6">
<input type="text" ngControl="userName" maxlength="45" class="form-control" [(ngModel)]="parent.userName" placeholder="UserName" #userName="ngForm" required data-is-unique/>
<validation-message control="userName"></validation-message>
</div>
</div>
<--code here-->
register.component.ts
import {Component} from 'angular2/core';
import {NgForm, FormBuilder, Validators, FORM_DIRECTIVES} from 'angular2/common';
import {ValidationService} from '../services/validation.service';
import {ValidationMessages} from './validation-messages.component';
#Component({
selector: 'register',
templateUrl: './views/register.html',
directives: [ROUTER_DIRECTIVES, ValidationMessages, FORM_DIRECTIVES],
providers: []
})
export class ParentSignUpComponent {
parentSignUpForm: any;
constructor(private _formBuilder: FormBuilder) {
this._stateService.isAuthenticatedEvent.subscribe(value => {
this.onAuthenticationEvent(value);
});
this.parent = new ParentSignUpModel();
this.parentSignUpForm = this._formBuilder.group({
'firstName': ['', Validators.compose([Validators.required, Validators.maxLength(45), ValidationService.nameValidator])],
'middleName': ['', Validators.compose([Validators.maxLength(45), ValidationService.nameValidator])],
'lastName': ['', Validators.compose([Validators.required, Validators.maxLength(45), ValidationService.nameValidator])],
'userName': ['', Validators.compose([Validators.required, ValidationService.checkUserName])]
});
}
}
validation-message.component
import {Component, Host} from 'angular2/core';
import {NgFormModel} from 'angular2/common';
import {ValidationService} from '../services/validation.service';
#Component({
selector: 'validation-message',
inputs: ['validationName: control'],
template: `<div *ngIf="errorMessage !== null" class="error-message"> {{errorMessage}}</div>`
})
export class ValidationMessages {
private validationName: string;
constructor (#Host() private _formDir: NgFormModel) {}
get errorMessage() {
let control = this._formDir.form.find(this.validationName);
for (let propertyName in control.errors) {
if (control.errors.hasOwnProperty(propertyName) && control.touched) {
return ValidationService.getValidatorErrorMessage(propertyName);
}
}
return null;
}
}
validation-service.ts
import {Injectable, Injector} from 'angular2/core';
import {Control} from 'angular2/common';
import {Observable} from 'rxjs/Observable';
import {Http, Response, HTTP_PROVIDERS} from 'angular2/http';
import 'rxjs/Rx';
interface ValidationResult {
[key:string]:boolean;
}
#Injectable()
export class ValidationService {
static getValidatorErrorMessage(code: string) {
let config = {
'required': 'This field is required!',
'maxLength': 'Field is too long!',
'invalidName': 'This field can contain only alphabets, space, dot, hyphen, and apostrophe.',
'userAlreadyInUse': 'UserName selected already in use! Please try another.'
};
return config[code];
}
static checkUserName(control: Control): Promise<ValidationResult> {
let injector = Injector.resolveAndCreate([HTTP_PROVIDERS]);
let http = injector.get(Http);
let alreadyExists: boolean;
if (control.value) {
return new Promise((resolve, reject) => {
setTimeout(() => {
http.get('/isUserNameUnique/' + control.value).map(response => response.json()).subscribe(result => {
if (result === false) {
resolve({'userAlreadyInUse': true});
} else {
resolve(null);
}
});
}, 1000);
});
}
}
}
Now, when i run, and give a username that already exists in db, the value of 'result' variable i am getting as false, which is expected and correct. But validation error message is not getting displayed. I am able to run and get validation error message for other custom validation functions. I am using Angular 2.0.0-beta.15. Can somebody help me to understand what could be the issue?

Answer 1

There are some known issues with async validation
https://github.com/angular/angular/issues/1068
https://github.com/angular/angular/issues/7538
https://github.com/angular/angular/issues/8118
https://github.com/angular/angular/issues/8923
https://github.com/angular/angular/issues/8022
This code can be simplified
return new Promise((resolve, reject) => {
setTimeout(() => {
http.get('/isUserNameUnique/' + control.value).map(response => response.json())
.subscribe(result => {
if (result === false) {
resolve({'userAlreadyInUse': true});
} else {
resolve(null);
}
});
}, 1000);
});
to
return http.get('/isUserNameUnique/' + control.value).map(response => response.json())
.timeout(200, new Error('Timeout has occurred.'));
.map(result => {
if (result === false) {
resolve({'userAlreadyInUse': true});
} else {
resolve(null);
}
}).toPromise();
Don't forget to import map, timeout, and toPromise.
If you use subscribe() instead of then() on the caller site, then you can event omit toPromise()

Answer 2

if you look into this -
'userName': ['', Validators.compose([Validators.required, ValidationService.checkUserName])] });
-- you can see I am using both synchronous and asynchronous validations together. When i changed method for checkUserName like 'Validators.composeAsync(ValidationService.checkUserName)' instead of Validators.compose method, error message got displayed.