qdouble · July 13, 2016 02:42 · Jul 13, 2016
diff --git a/Username Validation b/Username Validation
@@ -0,0 +1,30 @@
+import { FormControl } from '@angular/forms';
+import { AsyncValidatorFn, ValidatorFn } from '@angular/forms/src/directives/validators';
+import { Control } from '@angular/common';
+import { Injectable } from '@angular/core';
+import { Http } from '@angular/http';
+import { Observable } from 'rxjs/Observable';
+import { ReplaySubject } from 'rxjs/ReplaySubject';
+import { API_USER_URL } from '../services/constants';
+
+@Injectable()
+export class UsernameValidator {
+  input: ReplaySubject<any>;
+  request: any;
+
+  constructor(private http: Http) {
+    this.input = new ReplaySubject(1);
+    this.request = this.input
+      .debounceTime(50)
+      .distinctUntilChanged()
+      .take(1)
+      .switchMap(input => this.http.get(`${API_USER_URL}/checkUsername?username=${input}`))
+      .map(r => r.json())
+      .catch(() => Observable.of(null));
+  }
+
+  usernameTaken = (control: FormControl): AsyncValidatorFn => {
+    this.input.next(control.value);
+    return this.request;
+  }
+}