Playing With Promises

.gitignore

node_modules

package.json

{
  "name": "promise-tests",
  "version": "0.0.1",
  "dependencies": {
    "q": "1.0.1",
    "underscore": "1.7.0",
    "jasmine-node": "1.14.5"
  }
}

service-spec.js

var UserService = require("./service");
var userService;

describe("user service with promises", function () {

  beforeEach(function () {
    userService = new UserService();
  });

  afterEach(function () {
    userService = null;
  });

  it("should successfully list all users", function (done) {
    userService.create({ title: "mr", name: "foo"})
      .then(function () { return userService.create({ title: "mrs", name: "bar"}); })
      .then(function () { return userService.clone(2, {name: "baz"}); })
      .then(function () {
        expect(userService.getAll()).toEqual([
          { title: "mr", name: "foo", id: 1},
          { title: "mrs", name: "bar", id: 2},
          { title: "mrs", name: "baz", id: 3}
        ]);

        done();
      })
      .done();
  });

  it("should fail with error 'There was an error finding the user'", function (done) {
    userService.create({ title: "mr", name: "foo"})
      .then(function () { return userService.create({ title: "mrs", name: "bar"}); })
      .then(function () { return userService.clone(4, {name: "baz"}); })
      .fail(function (err) {
        expect(err.message).toEqual("There was an error finding the user");
        done();
      })
      .done();
  });

  it("should fail with error 'User must have a name'", function (done) {
    userService.create({ title: "mr", name: "foo"})
      .then(function () { return userService.create({ title: "mrs", name: "bar"}); })
      .then(function () { return userService.clone(2, {name: ""}); })
      .fail(function (err) {
        expect(err.message).toEqual("User must have a name");
        done();
      })
      .done();
  });

  it("should fail with error 'User with that name already exists'", function (done) {
    userService.create({ title: "mr", name: "foo"})
      .then(function () { return userService.create({ title: "mrs", name: "bar"}); })
      .then(function () { return userService.clone(2, {name: "bar"}); })
      .fail(function (err) {
        expect(err.message).toEqual("User with that name already exists");
        done();
      })
      .done();
  });
});

service.js

var q = require("q");
var _ = require("underscore");

var UserService = function () {
  var users = [];
  var insertId = 0;

  return {
    get: function (id) {
      var deferred = q.defer();

      var user = _.findWhere(users, {id: id});
      if (!user) {
        deferred.reject(new Error("There was an error finding the user"));
      } else {
        deferred.resolve(_.clone(user));
      }

      return deferred.promise;
    },

    getAll: function () {
      return users;
    },

    create: function (data) {
      var deferred = q.defer();

      if (!data.name || data.name === "") {
        deferred.reject(new Error("User must have a name"));
        return deferred.promise;
      }

      var nameAlreadyTaken = _.findWhere(users, {name: data.name});
      if (nameAlreadyTaken) {
        deferred.reject(new Error("User with that name already exists"));
        return deferred.promise;
      }

      insertId++;
      data.id = insertId;
      users.push(data);

      deferred.resolve(data);
      return deferred.promise;
    },

    clone: function (userId, overrides) {
      var deferred = q.defer();

      this.get(userId)
        .then(function (data) {
          var clonedUser = _.extend(data, overrides);
          delete clonedUser.id;
          return this.create(clonedUser);
        }.bind(this))
        .then(function (data) {
          deferred.resolve(data);
        })
        .fail(function (err) {
          deferred.reject(err);
        });

      return deferred.promise;
    }
  };
};

module.exports = UserService;