TypeError: Cannot read property 'router' of null Angular2 Router

Below is my component. Point of error is the this.router.navigate() part. After login, I wanna redirect the user to a different page, something similar to $state.go('dashboard').

import { Component } from '@angular/core';
import { Router } from '@angular/router';

import { AngularFire } from 'angularfire2';

@Component({
  templateUrl: 'app/auth/login.component.html'
})

export class LoginComponent {
  constructor(private af: AngularFire, private router: Router) { }
  onSubmit(formData) {
    if(formData.valid) {
      console.log(formData.value);
      this.af.auth.login({
        email: formData.value.email,
        password: formData.value.password
      }).then(function(success) {
        console.log(success);
        this.router.navigate(['/dashboard']);
      }).catch(function(err) {
        console.log(err);
        this.router.navigate(['/dashboard']);
      })
    }
  }
}

And I keep getting this error. Please enlighten me, what am I doing wrong?

You have to use Arrow function instead of function inside .then's success & catch callback's. Due to which inside success & catch callback function you're loosing component this(context).

Code

this.af.auth.login({
   email: formData.value.email,
   password: formData.value.password
}).then(
   //used Arrow function here
   (success)=> {
      console.log(success);
      this.router.navigate(['/dashboard']);
   }
).catch(
   //used Arrow function here
   (err)=> {
      console.log(err);
      this.router.navigate(['/dashboard']);
   }
)