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• Are document-oriented databases any more suitable than relational ones for persisting objects?

  - by Owen Fraser-Green

  In terms of database usage, the last decade was the age of the ORM with hundreds competing to persist our object graphs in plain old-fashioned RMDBS. Now we seem to be witnessing the coming of age of document-oriented databases. These databases are highly optimized for schema-free documents but are also very attractive for their ability to scale out and query a cluster in parallel. Document-oriented databases also hold a couple of advantages over RDBMS's for persisting data models in object-oriented designs. As the tables are schema-free, one can store objects belonging to different classes in an inheritance hierarchy side-by-side. Also, as the domain model changes, so long as the code can cope with getting back objects from an old version of the domain classes, one can avoid having to migrate the whole database at every change. On the other hand, the performance benefits of document-oriented databases mainly appear to come about when storing deeper documents. In object-oriented terms, classes which are composed of other classes, for example, a blog post and its comments. In most of the examples of this I can come up with though, such as the blog one, the gain in read access would appear to be offset by the penalty in having to write the whole blog post "document" every time a new comment is added. It looks to me as though document-oriented databases can bring significant benefits to object-oriented systems if one takes extreme care to organize the objects in deep graphs optimized for the way the data will be read and written but this means knowing the use cases up front. In the real world, we often don't know until we actually have a live implementation we can profile. So is the case of relational vs. document-oriented databases one of swings and roundabouts? I'm interested in people's opinions and advice, in particular if anyone has built any significant applications on a document-oriented database.

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• How do I get save (no exclamation point) semantics in an ActiveRecord transaction?

  - by James A. Rosen

  I have two models: Person and Address which I'd like to create in a transaction. That is, I want to try to create the Person and, if that succeeds, create the related Address. I would like to use save semantics (return true or false) rather than save! semantics (raise an ActiveRecord::StatementInvalid or not). This doesn't work because the user.save doesn't trigger a rollback on the transaction: class Person def save_with_address(address_options = {}) transaction do self.save address = Address.build(address_options) address.person = self address.save end end end (Changing the self.save call to an if self.save block around the rest doesn't help, because the Person save still succeeds even when the Address one fails.) And this doesn't work because it raises the ActiveRecord::StatementInvalid exception out of the transaction block without triggering an ActiveRecord::Rollback: class Person def save_with_address(address_options = {}) transaction do save! address = Address.build(address_options) address.person = self address.save! end end end The Rails documentation specifically warns against catching the ActiveRecord::StatementInvalid inside the transaction block. I guess my first question is: why isn't this transaction block... transacting on both saves?

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• need advice on Zend framework Application architecture, or say approach dealing with modules

  - by simple

  Let me start with the things that I did and how am I using some things to get results I have set up modular structure as: application/ /configs /layouts /models /modules /users /profile /frontend /backend /controllers /views .... I write a plugin that does addes changes with FrontController-setModuleControllerDirectoryName() FrontController-addModuleDirectory() and It is all good I have a changed all the directories according weather admin page is requested in the url or not (it is some thing like /admin/some/some) Let's say I have a single layout for anything that is related to Profile viewing , in this case the "Profile" module. The Profile layout is divided into three parts In the layout I was pulling out the Profile/PhotoController 's index action with a action() $this->action('index', 'photo', 'profile'); Then I have faced few issues 1. Can get passed Params inside the Photo Controller when calling ( profile/profile/index); 2. found out that helper Action() is evil cause it starts another dispatching loop =) --- and now I am thinking that my approach on plugging in controllers modules into layout also evil =). anyhow how Should I deal with plugging in some controllers (another module controllers) into the layout ?

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• Data Annotations on ViewModels or Domain Objects

  - by Ahmad

  Where would data annotations be more suitable: ViewModels or Domain Objects or Both I am struggling to decide where these will be more suited. I have not as yet fully utilized them but this question came to mind. From most of the examples I have seen, they are generally placed on Models and simply use the required attributes for validation using ModelState.IsValid. I have also seen another question on SO where the use of data annotations alone is not sufficient and advocate. Option 1 - I will still need to validate again in my service layer. ( I think that my service layer should be complete and this include validation, since its planned to be used elsewhere) Option 2 - How will I then get the benefits of the built in validation both client and server side. Option 3 - there will be a repetition of validation logic, however I was wondering if one could use a MetaData class approach that can be used for both ViewModels and Domain Objects. ( This is completely of the top of my head, so it may be nonsensical) I wonder if this question even makes sense. If not, can someone please help in understanding this better. Have I completely misunderstood the use of data annotations?

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• Should I write more SQL to be more efficient, or less SQL to be less buggy?

  - by RenderIn

  I've been writing a lot of one-off SQL queries to return exactly what a certain page needs and no more. I could reuse existing queries and issue a number of SQL requests linear to the number of records on the page. As an example, I have a query to return People and a query to return Job Details for a person. To return a list of people with their job details I could query once for people and then once for each person to retrieve their job details. I've found that in most cases that solution returns things in a reasonable amount of time, but I don't know how well it will scale in my environment. Instead I've been writing queries to join people + job details, or people + salary history, etc. I'm looking at my models and I see how I could shave off maybe 30% of my code if I were to re-use existing queries. This is a big temptation. Is it a bad thing to go for reuse over efficiency in general or does it all come down to the specific situation? Should I first do it the easy way and then optimize later, or is it best to get the code knocked out while everything is fresh in my mind? Thoughts, experiences?

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• Rails - Seeking a Dry authorization method compatible with various nested resources

  - by adam

  Consensus is you shouldn't nest resources deeper than 1 level. So if I have 3 models like this (below is just a hypothetical situation) User has_many Houses has_many Tenants and to abide by the above i do map.resources :users, :has_many => :houses map.resorces :houses, :has_many => :tenants Now I want the user to be able edit both their houses and their tenants details but I want to prevent them from trying to edit another users houses and tenants by forging the user_id part of the urls. So I create a before_filter like this def prevent_user_acting_as_other_user if User.find_by_id(params[:user_id]) != current_user() @current_user_session.destroy flash[:error] = "Stop screwing around wiseguy" redirect_to login_url() return end end for houses that's easy because the user_id is passed via edit_user_house_path(@user, @house) but in the tenents case tenant house_tenent_path(@house) no user id is passed. But I can get the user id by doing @house.user.id but then id have to change the code above to this. def prevent_user_acting_as_other_user if params[:user_id] @user = User.find(params[:user_id] elsif params[:house_id] @user = House.find(params[:house_id]).user end if @user != current_user() #kick em out end end It does the job, but I'm wondering if there is a more elegant way. Every time I add a new resource that needs protecting from user forgery Ill have to keep adding conditionals. I don't think there will be many cases but would like to know a better approach if one exists.

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• Seed has_many relation using mass assignment

  - by rnd

  Here are my two models: class Article < ActiveRecord::Base attr_accessible :content has_many :comments end class Comment < ActiveRecord::Base attr_accessible :content belongs_to :article end And I'm trying to seed the database in seed.rb using this code: Article.create( [{ content: "Hi! This is my first article!", comments: [{content: "It sucks"}, {content: "Best article ever!"}] }], without_protection: true) However rake db:seed gives me the following error message: rake aborted! Comment(#28467560) expected, got Hash(#13868840) Tasks: TOP => db:seed (See full trace by running task with --trace) It is possible to seed the database like this? If yes a follow-up question: I've searched some and it seems that to do this kind of (nested?) mass assignment I need to add 'accepts_nested_attributes_for' for the attributes I want to assign. (Possibly something like 'accepts_nested_attributes_for :article' for the Comment model) Is there a way to allow this similar to the 'without_protection: true'? Because I only want to accept this kind of mass assignment when seeding the database.

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• Populating dropdownlist in asp.net mvc doesn't seem to work for me...

  - by Pandiya Chendur

  I use a dropdownlist in one of my create.aspx but it some how doesnt seem to work... public IEnumerable<Materials> FindAllMeasurements() { var mesurements = from mt in db.MeasurementTypes select new Materials() { Id= Convert.ToInt64(mt.Id), Mes_Name= mt.Name }; return mesurements; } and my controller, public ActionResult Create() { var mesurementTypes = consRepository.FindAllMeasurements().AsEnumerable(); ViewData["MeasurementType"] = new SelectList(mesurementTypes, "Id", "Mes_Name"); return View(); } and my create.aspx has this, <p> <label for="MeasurementTypeId">MeasurementType:</label> <%= Html.DropDownList("MeasurementType", ViewData["MeasurementType"])%> <%= Html.ValidationMessage("MeasurementTypeId", "*") %> </p> When i execute this i got these errors, System.Web.Mvc.HtmlHelper<CrMVC.Models.Material>' does not contain a definition for 'DropDownList' and the best extension method overload 'System.Web.Mvc.Html.SelectExtensions.DropDownList(System.Web.Mvc.HtmlHelper, string, System.Collections.Generic.IEnumerable<System.Web.Mvc.SelectListItem>)' has some invalid arguments 2.cannot convert from 'object' to 'System.Collections.Generic.IEnumerable<System.Web.Mvc.SelectListItem>

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• Python unittest (using SQLAlchemy) does not write/update database?

  - by Jerry

  Hi, I am puzzled at why my Python unittest runs perfectly fine without actually updating the database. I can even see the SQL statements from SQLAlchemy and step through the newly created user object's email -- ...INFO sqlalchemy.engine.base.Engine.0x...954c INSERT INTO users (user_id, user_name, email, ...) VALUES (%(user_id)s, %(user_name)s, %(email)s, ...) ...INFO sqlalchemy.engine.base.Engine.0x...954c {'user_id': u'4cfdafe3f46544e1b4ad0c7fccdbe24a', 'email': u'[email protected]', ...} > .../tests/unit_tests/test_signup.py(127)test_signup_success() -> user = user_q.filter_by(user_name='test').first() (Pdb) n ...INFO sqlalchemy.engine.base.Engine.0x...954c SELECT users.user_id AS users_user_id, ... FROM users WHERE users.user_name = %(user_name_1)s LIMIT 1 OFFSET 0 ...INFO sqlalchemy.engine.base.Engine.0x...954c {'user_name_1': 'test'} > .../tests/unit_tests/test_signup.py(128)test_signup_success() -> self.assertTrue(isinstance(user, model.User)) (Pdb) user <pweb.models.User object at 0x9c95b0c> (Pdb) user.email u'[email protected]' Yet at the same time when I login to the test database, I do not see the new record there. Is it some feature from Python/unittest/SQLAlchemy/Pyramid/PostgreSQL that I'm totally unaware of? Thanks. Jerry

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• asp.net mvc multiple fckeditors field

  - by mazhar kaunain baig

  how to add multiple fckeditor field on asp.net mvc page ok here is the code <% foreach (var OrganizationMeta in ((IEnumerable<Egovt.Models.OrganizationMeta>)ViewData["OrganizationMeta"])) { %> <% if (OrganizationMeta.vcr_DateType == "text") { %> <% TempData["OrganizationMeta"] = OrganizationMeta.vcr_MetaKey + Lang.int_LangId; %> <% Html.RenderPartial("ControlRender"); %> <% } %> <% } %> </div> controlrender <script src="<%= Url.Content("~/Content/js/fck/fckeditor.js") %>" type="text/javascript"></script> <script type="text/javascript"> window.onload = function() { var sBasePath = '<%= Url.Content("~/Content/js/fck/") %>'; var oFCKeditor = new FCKeditor('<%=TempData["OrganizationMeta"] %>'); oFCKeditor.BasePath = sBasePath; oFCKeditor.ReplaceTextarea(); } </script> <%= Html.TextArea(TempData["OrganizationMeta"].ToString(),"", new { @name = TempData["OrganizationMeta"] })%> How will i implement it

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• Problem using Lazy<T> from within a generic abstract class

  - by James Black

  I have a generic class that all my DAO classes derive from, which is defined below. I also have a base class for all my entities, but that is not generic. The method GetIdOrSave is going to be a different type than how I defined SabaAbstractDAO, as I am trying to get the primary key to fulfill the foreign key relationships, so this function goes out to either get the primary key or save the entity and then get the primary key. The last code snippet has a solution on how it will work if I get rid of the generic part, so I think this can be solved by using variance, but I can't figure out how to write an interface that will compile. public abstract class SabaAbstractDAO<T> { ... public K GetIdOrSave<K>(K item, Lazy<SabaAbstractDAO<BaseModel>> lazyitemdao) where K : BaseModel { if (item != null && item.Id.IsNull()) { var itemdao = lazyitemdao.Value; item.Id = itemdao.retrieveID(item); if (item.Id.IsNull()) { return itemdao.SaveData(item); } } return item; } } I am getting this error, when I try to compile: Argument 2: cannot convert from 'System.Lazy<ORNL.HRD.LMS.Dao.SabaCourseDAO>' to 'System.Lazy<ORNL.HRD.LMS.Dao.SabaAbstractDAO<ORNL.HRD.LMS.Models.BaseModel>>' I am trying to call it this way: GetIdOrSave(input.OfferingTemplate, new Lazy<SabaCourseDAO>( () => { return new SabaCourseDAO() { Dao = Dao }; }) ); If I change the definition to this, it works. public K GetIdOrSave<K>(K item, Lazy<SabaCourseDAO> lazyitemdao) where K : BaseModel { So, how can I get this to compile using variance (if needed) and generics, so I can have a very general method that will only work with BaseModel and AbstractDAO<BaseModel>? I expect I should only need to make the change in the method and perhaps abstract class definition, the usage should be fine.

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• Spree customize/extend user roles and permissions

  - by swapnil

  I am trying to specify some custom roles in Spree for example role 'client' and extend the permissions to access the admin section for this role. This user will be able to access only those Product created by that user. Concept is letting a user with role 'client' manage only products and other certain Models. To start with I added CanCan plugin and defined a RoleAbility Class in role_ability.rb Just following this post : Spree Custom Roles Permissions class RoleAbility include CanCan::Ability def initialize(user) user ||= User.new if user.has_role? 'admin' can :manage, :all elsif user.has_role? 'client_admin' can :read, Product can :admin, Product end end end Added this to an initializer : config/initializers/spree.rb Ability.register_ability(RetailerAbility) Also extended admin_products_controller_decorator.rb :app/controllersadmin_products_controller_decorator.rb Admin::ProductsController.class_eval do def authorize_admin authorize! :admin, Product authorize! params[:action].to_sym, Product end end But I am getting flash message 'Authorisation Failure' Trying to find some luck, I referred following links A github gist for Customizing Spree Roles : https://gist.github.com/1277326 Here's a similar issue what I am facing : http://groups.google.com/group/spree-user/browse_thread/thread/1e819e10410d03c5/23b269e09c7ed47e All efforts in vain... Any pointers of what is going on here highly appreciated ? Thanks in advance.

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• How to get root as '/' with Kohana3, base_url and mod rewrite.

  - by Drew

  Hi all! I've only just started using Kohana ( 3 hours ago), and so far it's blown my socks off (and I'm wearing slippers, so that's quite impressive). Right now, I have a controller 'Controller_FrontPage' with associated views and models and I'm trying to get it accesible from the root of my website (eg, http://www.mysite.com/). If I edit the default controller in the bootstrap from: Route::set('default', '(<controller>(/<action>(/<id>)))') ->defaults(array( 'controller' => 'welcome', 'action' => 'index', )); to 'controller' => '', I get an error, could not find controller_ (which makes sense), and if I change it to 'controller' => '/', I get an error, could not find controller_/ (which also makes sense). If I set 'controller' => 'FrontPage', everything works fine, but all my links (html::anchor(...)) point to http://www.mysite.com/FrontPage/*. Is there a way to have all the anchors point to http://www.mysite.com/*?

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• Type or namespace could not be found

  - by Jason Shultz

  I'm using LINQ to SQL to connect my database to my home page. I created my datacontext (named businessModel.dbml) In it I have two tables named Category and Business. In home controller I reference the model and attempt to return to the view the table: var dataContext = new businessModelDataContext(); var business = from b in dataContext.Businesses select b; ViewData["WelcomeMessage"] = "Welcome to Jerome, Arizona!"; ViewData["MottoMessage"] = "Largest Ghost Town in America!"; return View(business); and in the view I have this: <%@ Import Namespace="WelcomeToJerome.Models" %> and <% foreach (business b in (IEnumerable)ViewData.Model) { %> <li><%= b.Title %></li> <% } %> Yet, in the view business is cursed with the red underline and say's that The type or namespace name 'business' could not be found (are you missing a using directive or an assembly reference?) What am I doing wrong? This has had me stumped all afternoon. link to all the code in pastebin: http://pastebin.com/es4RnS2q

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• Creating has_many :through records 2x times

  - by antiarchitect

  I have models class Question < ActiveRecord::Base WEIGHTS = %w(medium hard easy) belongs_to :test has_many :answers, :dependent => :destroy has_many :testing_questions end class Testing < ActiveRecord::Base belongs_to :student, :foreign_key => 'user_id' belongs_to :subtest has_many :testing_questions, :dependent => :destroy has_many :questions, :through => :testing_questions end So when I try to bind questions to testing on it's creation: >> questions = Question.all ... >> questions.count => 3 >> testing = Testing.create(:user_id => 3, :subtest_id => 1, :questions => questions) Testing Columns (0.9ms) SHOW FIELDS FROM `testings` SQL (0.1ms) BEGIN SQL (0.1ms) COMMIT SQL (0.1ms) BEGIN Testing Create (0.3ms) INSERT INTO `testings` (`created_at`, `updated_at`, `user_id`, `subtest_id`) VALUES('2010-05-18 00:53:05', '2010-05-18 00:53:05', 3, 1) TestingQuestion Columns (0.9ms) SHOW FIELDS FROM `testing_questions` TestingQuestion Create (0.3ms) INSERT INTO `testing_questions` (`question_id`, `created_at`, `updated_at`, `testing_id`) VALUES(1, '2010-05-18 00:53:05', '2010-05-18 00:53:05', 31) TestingQuestion Create (0.4ms) INSERT INTO `testing_questions` (`question_id`, `created_at`, `updated_at`, `testing_id`) VALUES(2, '2010-05-18 00:53:05', '2010-05-18 00:53:05', 31) TestingQuestion Create (0.3ms) INSERT INTO `testing_questions` (`question_id`, `created_at`, `updated_at`, `testing_id`) VALUES(3, '2010-05-18 00:53:05', '2010-05-18 00:53:05', 31) TestingQuestion Create (0.3ms) INSERT INTO `testing_questions` (`question_id`, `created_at`, `updated_at`, `testing_id`) VALUES(1, '2010-05-18 00:53:05', '2010-05-18 00:53:05', 31) TestingQuestion Create (0.3ms) INSERT INTO `testing_questions` (`question_id`, `created_at`, `updated_at`, `testing_id`) VALUES(2, '2010-05-18 00:53:05', '2010-05-18 00:53:05', 31) TestingQuestion Create (0.3ms) INSERT INTO `testing_questions` (`question_id`, `created_at`, `updated_at`, `testing_id`) VALUES(3, '2010-05-18 00:53:05', '2010-05-18 00:53:05', 31) SQL (90.2ms) COMMIT => #<Testing id: 31, subtest_id: 1, user_id: 3, created_at: "2010-05-18 00:53:05", updated_at: "2010-05-18 00:53:05"> There is 6 SQL queries and 6 records in testing_questions are created. Why?

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• Have any software engineers gotten math degrees later in their careers?

  - by vin

  I have a bachelors in computer science and worked the last 12 years as a software engineer. I'm bored with doing general development work, so I want to specialize. I'm thinking about getting a master's degree in math so I can build math models and write algorithms to implement them. I'm unsure what type of work I'd do (financial, gaming, graphics, science, research, etc) but I'm open minded. I would need to refresh my undergrad math skills (which are old and faded), but I loved algebra and calculus. I've been working with couple statisticians so I've been finding myself more interested in statistics. Since I'm a parent supporting a household, I would have to continue working while studying. Have any software engineers taken this route? (Specifically, going from BS in comp sci to MS in math.) If so, what advice do you have for coursework, financing, and getting a job that combines programming with advanced math? How abundant are these kinds of jobs? I'm not sure where one starts. Also, how do you hop from a BS to an MS in a different subject?

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• NHibernate collections: many-to-many relationships

  - by Brad Heller

  I've got two models, a Product model and a ShoppingCart model. The ShoppingCart model has a collection of products as a property called Products (List). Here is the mapping for my ShoppingCart model. <class name="MyProject.ShoppingCart, MyProject" table="ShoppingCarts"> <id name="Id" column="Id"> <generator class="native" /> </id> <many-to-one name="Company" class="MyProject.Company, MyProject" column="CompanyId" /> <property name="ExternalId" column="GUID" generated="insert" /> <property name="Name" column="Name" /> <property name="Total" column="Total" /> <property name="CreationDate" column="CreationDate" generated="insert" /> <property name="UpdatedDate" column="UpdatedDate" generated="always" /> <bag name="Products" table="ShoppingCartContents" lazy="false"> <key column="ShoppingCartId" /> <many-to-many column="ProductId" class="MyProjectMyProject.Product, MyProject" fetch="join" /> </bag> </class> When I try to save to the DB, the ShoppingCart is saved, but the mapping rows in ShoppingCartContents aren't save, making me thing that there's an issue with the mapping. Where am I going wrong here?

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• PHP + MYSQLI: Variable parameter/result binding with prepared statements.

  - by Brian Warshaw

  In a project that I'm about to wrap up, I've written and implemented an object-relational mapping solution for PHP. Before the doubters and dreamers cry out "how on earth?", relax -- I haven't found a way to make late static binding work -- I'm just working around it in the best way that I possibly can. Anyway, I'm not currently using prepared statements for querying, because I couldn't come up with a way to pass a variable number of arguments to the bind_params() or bind_result() methods. Why do I need to support a variable number of arguments, you ask? Because the superclass of my models (think of my solution as a hacked-up PHP ActiveRecord wannabe) is where the querying is defined, and so the find() method, for example, doesn't know how many parameters it would need to bind. Now, I've already thought of building an argument list and passing a string to eval(), but I don't like that solution very much -- I'd rather just implement my own security checks and pass on statements. Does anyone have any suggestions (or success stories) about how to get this done? If you can help me solve this first problem, perhaps we can tackle binding the result set (something I suspect will be more difficult, or at least more resource-intensive if it involves an initial query to determine table structure).

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• Controller class not available in Add View ASP.NET MVC

  - by Tassadaque

  Hi I have created the following controller i want to add view that should have the data access class UserMagnament.Controller.menuitems but when i add view by right clicking on view folder,it is not showing "UserMagnament.Controller.menuitems" in add data class using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.Mvc; using UserManagement.Models; namespace UserManagement.Controllers { public class menuitems { EvoLetDataContext db1 = new EvoLetDataContext(); public menuitems() { } public IQueryable<UMUserType> menuitems() { return db1.UMUserTypes; //this.Packages = _SysPackage; //this.Modules = _SysModule; } public List<SysPackage> Packages { get; private set; } public List<SysModule> Modules { get; private set; } } public class Default1Controller : Controller { // // GET: /Default1/ public ActionResult Index() { return View(new menuitems()); } } }

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• Redirecting users after destroy

  - by mathee

  I have 3 models: Questions, Answers, and Profiles (I know, it should be called "Users"). When you view a question Q, I query the database for the answers to Q. (They are linked by id.) In the view, the current user has the option to delete his answer by clicking on the destroy link displayed next to his answer: %table %tr %td Answers: - @answers.each do |a| %tr %td - @provider = Profile.find(a.provider) %i #{h @provider.username} said: %br #{h a.description} %td = link_to 'View full answer', a %td - if a.provider == @profile.id #{link_to 'Delete my answer', a, :confirm => 'Are you sure?', :method => :delete} The problem is that when the user clicks on the destroy link, it redirects to the /answers/index. I want it to redirect to /questions/Q. What's the best way to do this? I know that there's a redirect_to method, but I don't know how to implement it when I want to redirect to an action for a different controller. It also needs to remember the question from which the answer is being deleted. I tried passing something like :question_id in link_to as: #{link_to 'Delete my answer', a, :confirm => 'Are you sure?', :question_id => @question.id, :method => :delete} In AnswersController#destroy: def destroy @answer = Answer.find(params[:id]) @answer.destroy respond_to do |format| format.html { redirect_to(answers_url) } format.xml { head :ok } end @question = Question.find(params[:question_id]) redirect_to question_path(@question) end The :question_id information is not passed to the destroy method, so I get this error: Couldn't find Question without an ID To confirm, I added a puts call before Question.find, and it returned nil.

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• ruby on rails one-to-many relationship

  - by fenec

  I would like to model a betting system relationship using the power of rails. so lets start with doing something very simple modelling the relationship from a user to a bet.i would like to have a model bet with 2 primary keys. here are my migrations enter code here class CreateBets < ActiveRecord::Migration def self.up create_table :bets do |t| t.integer :user_1_id t.integer :user_2_id t.integer :amount t.timestamps end end def self.down drop_table :bets end end class CreateUsers < ActiveRecord::Migration def self.up create_table :users do |t| t.string :name t.timestamps end end def self.down drop_table :users end end the models enter code here class Bet < ActiveRecord::Base belongs_to :user_1,:class_name=:User belongs_to :user_2,:class_name=:User end class User < ActiveRecord::Base has_many :bets, :foreign_key =:user_1) has_many :bets, :foreign_key =:user_2) end when i test here in the console my relationships I got an error enter code here u1=User.create :name="aa" = # u2=User.create :name="bb" = # b=Bet.create(:user_1=u1,:user_2=u2) *****error***** QUESTIONS: 1 How do I define the relationships between these tables correctly? 2 are there any conventions to name the attributes (ex:user_1_id...) thank you for your help

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• ASP.NET MVC Patterns

  - by Sam Striano

  Hello, I am fairly new to MVC, but after playing with it (MVC 3/Razor), I am hooked. I have a few questions: 1) What is the best, or most widely used pattern to develop MVC apps in? Repository, DDD, UOW? 2) I am using the Entity Framework 4, so could some please explain to me or point me to a good source that will explain the Repository Pattern w/EF4? Doesn't EF4 take place as the business layer and the data access layer? Does the Repository Pattern even provide a benefit? 3) Also, one last question, could someone explain the whole relationship between the Controller, the Model and the View? I get the basics, but maybe a little more in depth of the correct way to use it. View Models - Say I have a view that displays customer info, and one that edits it, should I have a view model and an edit model, or can the be passed around? 4) Examples?? Thanks for the help up front, $("Sam") ** EDIT ** Am I on the right track here: Public Class HomeController Inherits System.Web.Mvc.Controller Function Index(ByVal id As Integer) As ActionResult Return View(New HomeModel) End Function <HttpPost()> _ Function Index(ByVal Model As HomeModel) As ActionResult Return View(Model) End Function End Class Public Class HomeModel Private _Repository As IRepository(Of Customer) Public Property Customer As Customer Public Sub New() End Sub Public Sub New(ByVal ID As Integer) _Repository = New CustomerRepository Customer = _Repository.GetByID(ID) End Sub End Class Public Interface IRepository(Of T) Function GetByID(ByVal ID As Integer) As T Sub Add(ByVal Entity As T) Sub Delete(ByVal Entity As T) End Interface Public Class CustomerRepository Implements IRepository(Of Customer) Public Sub Add(ByVal Entity As Customer) Implements IRepository(Of Customer).Add End Sub Public Sub Delete(ByVal Entity As Customer) Implements IRepository(Of Customer).Delete End Sub Public Function GetByID(ByVal ID As Integer) As Customer Implements IRepository(Of Customer).GetByID Return New Customer With {.ID = ID, .FirstName = "Sam", .LastName = "Striano"} End Function End Class Public Class Customer Public Property ID As Integer Public Property FirstName As String Public Property LastName As String End Class

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• Html.ListBox() and MultiselectList

  - by Ivan90

  Hi guys, I've a little problem with an Html.ListBox! I am developing a personal blog in ASP.NET MVC 1.0 and I created an adminpanel where I can add and edit a post! During this two operations, I can add also tags! I think of use an Html.ListBox() helper to list all tags, and so I can select multiple tags to add in a post! The problem isn't during the add mode, but in the edit mode, where I have to pre-select post's tags! I read that I have to use a MultiSelectList and so in its constructor pass, tags' list and tag's list(pre-selected value). But I don't know how to use this class! I post, some code: This is my models method that get all list tags in selectlist public IEnumerable<SelectListItem> GetTagsListBox() { return from t in db.Tags orderby t.IDTag descending select new SelectListItem { Text = t.TagName, Value = t.IDTag.ToString(), }; } So in Edit (Get and Post), Add(Get and Post) I use a ViewData to pass this list in Html.ListBox(). ViewData["Tags"] = tagdb.GetTagsListBox(); And in my view <%=Html.ListBox("Tags",ViewData["Tags"] as SelectList) %> So with this code it's ok in Add Mode! But in Edit Mode I need to pre-select those values! So Now, of course I have to create a method that get all tagsbypostid! and then in ViewData what Must I to pass? Any suggest?

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• How to use associated Model as datasource for DataView

  - by Chris Gilbert

  I have a Model structure as shown below and I want to know how to use the Bookings array as the datasource of my DataView. Model Structure: Client ClientId Name Bookings (HasManyAssociation) Contacts (HasManyAssociation) AjaxProxy JsonReader (ImplicitIncludes is set to true so child models are created with one call) Booking BookingNodeId BookingDetails Contact ContactNodeId ContactDetails The above gives me a data structure as follows: Client Bookings[ Booking Booking ] Contacts[ Contact Contact ] What I want to be able to do is either, create a Store from my Bookings array and then use that store as the datasource for my DataView OR directly use the Bookings array as the datasource (I don't really care how I do it to be honest). If I setup the AjaxProxy on my Booking model it works fine but then obviously I cannot automatically create my Client and Contacts when I load my JSON. It seems to me to make sense that the Client model, being the top level model hierarchically, is the one to load the data. EDIT: I figured it out as follows (with special thanks to handet87 below for his dataview.setStore() pointer). The key in this case is to know that creating the relationship actually sets up another store called, in this case BookingsStore and ContactsStore. All I needed to do was dataview.setStore("BookingsStore")

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• Postgres error with Sinatra/Haml/DataMapper on Heroku

  - by sevennineteen

  I'm trying to move a simple Sinatra app over to Heroku. Migration of the Ruby app code and existing MySQL database using Taps went smoothly, but I'm getting the following Postgres error: PostgresError - ERROR: operator does not exist: text = integer LINE 1: ...d_at", "post_id" FROM "comments" WHERE ("post_id" IN (4, 17,... ^ HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts. It's evident that the problem is related to a type mismatch in the query, but this is being issued from a Haml template by the DataMapper ORM at a very high level of abstraction, so I'm not sure how I'd go about controlling this... Specifically, this seems to be throwing up on a call of p.comments from my Haml template, where p represents a given post. The Datamapper models are related as follows: class Post property :id, Serial ... has n, :comments end class Comment property :id, Serial ... belongs_to :post end This works fine on my local and current hosted environment using MySQL, but Postgres is clearly more strict. There must be hundreds of Datamapper & Haml apps running on Postgres DBs, and this model relationship is super-conventional, so hopefully someone has seen (and determined how to fix) this. Thanks!

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