2.js

Syncin.LoginController = Ember.Controller.extend({
  login: function() {
    var data = {
      username: this.get('username'),
      password: this.get('password')
    }
    var self = this;

    self.set('errorMessage', null);

    Ember.$.post('/api/v1/sessions', data).then(function(response){
      self.set('errorMessage', response.message)

      if (response.success) {
        alert("success token is" + response.token);
        self.controller.set('loggedIn', true);
      }
      else {
        alert("wrong username or password");
      }
    })
  },

  logout: function() {
    this.set('loggedIn', false);
    alert("You are logged out.");
  },
  reset: function() {
    this.set("username", "");
    this.set("password", "");
    this.set("errorMessage", "");
  }
});

sessions_controller.rb

class Api::V1::SessionsController < ApplicationController
  respond_to :json

  def create
    username = params[:username]
    password = params[:password]

    if username == "admin" && password == "123456"
      render :json => {:success => true, :token => "abcdefgh"}
    else
      render :json => {:success => false, :message => "Invalid username or password"}
    end
  end
end