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  • Is there a scheduling algorithm that optimizes for "maker's schedules"?

    - by John Feminella
    You may be familiar with Paul Graham's essay, "Maker's Schedule, Manager's Schedule". The crux of the essay is that for creative and technical professionals, meetings are anathema to productivity, because they tend to lead to "schedule fragmentation", breaking up free time into chunks that are too small to acquire the focus needed to solve difficult problems. In my firm we've seen significant benefits by minimizing the amount of disruption caused, but the brute-force algorithm we use to decide schedules is not sophisticated enough to handle scheduling large groups of people well. (*) What I'm looking for is if there's are any well-known algorithms which minimize this productivity disruption, among a group of N makers and managers. In our model, There are N people. Each person pi is either a maker (Mk) or a manager (Mg). Each person has a schedule si. Everyone's schedule is H hours long. A schedule consists of a series of non-overlapping intervals si = [h1, ..., hj]. An interval is either free or busy. Two adjacent free intervals are equivalent to a single free interval that spans both. A maker's productivity is maximized when the number of free intervals is minimized. A manager's productivity is maximized when the total length of free intervals is maximized. Notice that if there are no meetings, both the makers and the managers experience optimum productivity. If meetings must be scheduled, then makers prefer that meetings happen back-to-back, while managers don't care where the meeting goes. Note that because all disruptions are treated as equally harmful to makers, there's no difference between a meeting that lasts 1 second and a meeting that lasts 3 hours if it segments the available free time. The problem is to decide how to schedule M different meetings involving arbitrary numbers of the N people, where each person in a given meeting must place a busy interval into their schedule such that it doesn't overlap with any other busy interval. For each meeting Mt the start time for the busy interval must be the same for all parties. Does an algorithm exist to solve this problem or one similar to it? My first thought was that this looks really similar to defragmentation (minimize number of distinct chunks), and there are a lot of algorithms about that. But defragmentation doesn't have much to do with scheduling. Thoughts? (*) Practically speaking this is not really a problem, because it's rare that we have meetings with more than ~5 people at once, so the space of possibilities is small.

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  • How do I get my snapshots in Nexus to appear in the m2eclipse dependency search?

    - by Brabster
    Hi, I've been working through the Nexus guide this weekend and I've got everything set up, to the point that I can publish a snapshot to my local nexus install. I can't seem to work out how to get m2eclipse to see the snapshot and offer it as an option in the Add Dependencies search panel. How do I do that? Thanks! In case it's of any use, my settings.xml is as follows: <settings xmlns="http://maven.apache.org/SETTINGS/1.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd"> <localRepository /> <interactiveMode /> <usePluginRegistry /> <offline /> <pluginGroups /> <servers> <server> <id>localSnap</id> <username>deployment</username> <password>*****</password> </server> </servers> <mirrors> <mirror> <!--This sends everything else to /public --> <id>nexus</id> <mirrorOf>*</mirrorOf> <url>http://localhost:8080/nexus/content/groups/public</url> </mirror> </mirrors> <profiles> <profile> <id>nexus</id> <!--Enable snapshots for the built in central repo to direct --> <!--all requests to nexus via the mirror --> <repositories> <repository> <id>central</id> <url>http://central</url> <releases> <enabled>true</enabled> </releases> <snapshots> <enabled>true</enabled> </snapshots> </repository> </repositories> <pluginRepositories> <pluginRepository> <id>central</id> <url>http://central</url> <releases> <enabled>true</enabled> </releases> <snapshots> <enabled>true</enabled> </snapshots> </pluginRepository> </pluginRepositories> </profile> </profiles> <activeProfiles> <!--make the profile active all the time --> <activeProfile>nexus</activeProfile> </activeProfiles> </settings>

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  • Handling exceptions raised in observers

    - by sparky
    I have a Rails (2.3.5) application where there are many groups, and each Group has_many People. I have a Group edit form where users can create new people. When a new person is created, they are sent an email (the email address is user entered on the form). This is accomplished with an observer on the Person model. The problem comes when ActionMailer throws an exception - for example if the domain does not exist. Clearly that cannot be weeded out with a validation. There would seem to be 2 ways to deal with this: A begin...rescue...end block in the observer around the mailer. The problem with this is that the only way to pass any feedback to the user would be to set a global variable - as the observer is out of the MVC flow, I can't even set a flash[:error] there. A rescue_from in the Groups controller. This works fine, but has 2 problems. Firstly, there is no way to know which person threw the exception (all I can get is the 503 exception, no way to know which person caused the problem). This would be useful information to be able to pass back to the user - at the moment, there is no way for me to let them know which email address is the problem - at the moment, I just have to chuck the lot back at them, and issue an unhelpful message saying that one of them is not correct. Secondly (and to a certain extent this make the first point moot) it seems that it is necessary to call a render in the rescue_from, or it dies with a rather bizarre "can't convert Array into String" error from webbrick, with no stack trace & nothing in the log. Thus, I have to throw it back to the user when I come across the first error and have to stop processing the rest of the emails. Neither of the solutions are optimal. It would seem that the only way to get Rails to do what I want is option 1, and loathsome global variables. This would also rely on Rails being single threaded. Can anyone suggest a better solution to this problem?

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  • Should an event-sourced aggregate root have access to the event sourcing repository?

    - by JD Courtoy
    I'm working on an event-sourced CQRS implementation, using DDD in the application / domain layer. I have an object model that looks like this: public class Person : AggregateRootBase { private Guid? _bookingId; public Person(Identification identification) { Apply(new PersonCreatedEvent(identification)); } public Booking CreateBooking() { // Enforce Person invariants var booking = new Booking(); Apply(new PersonBookedEvent(booking.Id)); return booking; } public void Release() { // Enforce Person invariants // Should we load the booking here from the aggregate repository? // We need to ensure that booking is released as well. var booking = BookingRepository.Load(_bookingId); booking.Release(); Apply(new PersonReleasedEvent(_bookingId)); } [EventHandler] public void Handle(PersonBookedEvent @event) { _bookingId = @event.BookingId; } [EventHandler] public void Handle(PersonReleasedEvent @event) { _bookingId = null; } } public class Booking : AggregateRootBase { private DateTime _bookingDate; private DateTime? _releaseDate; public Booking() { //Enforce invariants Apply(new BookingCreatedEvent()); } public void Release() { //Enforce invariants Apply(new BookingReleasedEvent()); } [EventHandler] public void Handle(BookingCreatedEvent @event) { _bookingDate = SystemTime.Now(); } [EventHandler] public void Handle(BookingReleasedEvent @event) { _releaseDate = SystemTime.Now(); } // Some other business activities unrelated to a person } With my understanding of DDD so far, both Person and Booking are seperate aggregate roots for two reasons: There are times when business components will pull Booking objects separately from the database. (ie, a person that has been released has a previous booking modified due to incorrect information). There should not be locking contention between Person and Booking whenever a Booking needs to be updated. One other business requirement is that a Booking can never occur for a Person more than once at a time. Due to this, I'm concerned about querying the query database on the read side as there could potentially be some inconsistency there (due to using CQRS and having an eventually consistent read database). Should the aggregate roots be allowed to query the event-sourced backing store by id for objects (lazy-loading them as needed)? Are there any other avenues of implementation that would make more sense?

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  • Zend Table Relationship Modeling with Composite Key

    - by emeraldjava
    I have a table with a composite primary key using four columns. mysql> describe leaguesummary; +------------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------------------+------------------+------+-----+---------+----------------+ | leagueid | int(10) unsigned | NO | PRI | NULL | auto_increment | | leaguetype | enum('I','T') | NO | PRI | NULL | | | leagueparticipantid | int(10) unsigned | NO | PRI | NULL | | | leaguestandard | int(10) unsigned | NO | | NULL | | | leaguedivision | varchar(5) | NO | PRI | NULL | | | leagueposition | int(10) unsigned | NO | | NULL | | I have the league object modelled as so (all plain enough mappings) <?php class Model_DbTable_League extends Zend_Db_Table_Abstract { protected $_name = 'league'; protected $_primary = 'id'; protected $_dependentTables = array('Model_DbTable_LeagueSummary'); And I've started like this on the new model class. I've mapped a simple reference map which returns all rows linked to the league id. // http://files.zend.com/help/Zend-Framework/zend.db.table.relationships.html // http://naneau.nl/2007/04/21/a-zend-framework-tutorial-part-one/ class Model_DbTable_LeagueSummary extends Zend_Db_Table_Abstract { protected $_name = "leaguesummary"; protected $_primary = array('leagueid', 'leaguetype','leagueparticipantid','leaguedivision'); protected $_referenceMap = array( 'Summary' => array( 'columns' => array('leagueid'), 'refTableClass' => 'Model_DbTable_League', 'refColumns' => array('id') ), ..... ); } ?> The simple case works when called from my controller public function listAction() { // action body $leagueTable = new Model_DbTable_League(); $this->view->leagues = $leagueTable->getLeagues(); $league = $leagueTable->getLeague(6); // work $summary = $league->findDependentRowset('Model_DbTable_LeagueSummary','Summary'); Zend_Debug::dump($summary,"",true); I'm not sure how i can define extra _referenceMap keys which will take extra contraint ket values. I would like to be able to define a set called 'MenA' in which the type and division values are hardcoded, and the league id is taken from the initial rowset. 'MenA' =>array( 'columns' => array('leagueid','leaguetype','leaguedivision'), 'refTableClass' => 'Model_DbTable_League', 'refColumns' => array("id","I","A") ) Is this style of mapping possible ie hardcoding the values into the 'refColumns'. The second crazy idea i had was to pass the variable values in as part of the third param of the findDependentRowset() method. $menA = $league->findDependentRowset('Model_DbTable_LeagueSummary','MenA',array("I","A")); Any suggestions on how I might use the Zend DB Table Relationship mapping correctly to do this would be appreciated. I'm not interested in the plain, old and ugly $db-select(a,b,c)-where(..) style solution.

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  • Keeping track of business rules within IT department?

    - by evaldas-alexander
    I am looking for the best way to keep track of the business rules for both developers and everybody else (support staff / management) in a startup enviroment. The challenge is that our business model requires quite a lot of different business rules, which are created pretty much on the fly and evolving organically after that. After running this project for 3+ years, we have so many of such rules that often the only way to be sure about what the application is supposed to do in a certain situation is to go find the module responsible for that process and analyze its code and comments. That is all fine as long as you have one single developer who created the entire application from the scratch, but every new developer needs to go over pretty much entire codebase in order to understand how the application works. Even bigger problem is that non technical employees don't even have that option and therefore are forced to ask me pretty much every day how some certain case would be handled by the application. Quick example - we only start charging for our customer campaigns once they have been active for at least 72 hours, but at the same time we stop creating invoices for campaigns that belong to insolvent accounts and close such accounts within a month of the first failed charge. That does not apply to accounts that are set to "non-chargeable" which most commonly belongs to us since we are using the service ourselves. The invoices are created on the 1st of each month and include charges from the previous month + any current balance that the account might have. However, some customers are charged only 4 days after their invoice has been generated due to issues with their billing department. In addition to that, invoices are also created when customer deactivates his campaign, but that can only be done once the campaign is not longer under mandatory 6 month contract, unless account manager approves early deactivation. I know, that's quite a lot of rules that need to be taken into account when answering a question "when do we bill our customers", but actually I could still append an asterisk at the end of each sentence in order to disclose some rare exceptions. Of course, it would be easiest just to keep the business rules to the minimum, but we need to adapt to changing marketplace - i.e. less than a year ago we had no contracts whatsoever. One idea that I had so far was a simplistic wiki with categories corresponding to areas such as "Account activation", "Invoicing", "Collection procedures" and so on. Another idea would be to have giant interactive flowchart showing the entire customer "life cycle" from prospecting to account deactivation. What are your experiences / suggestions?

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  • Is there simple way how to join two RouteValueDictionary values to pass parameters to Html.ActionLin

    - by atagaew
    Hi. Look on my code that i created in a partial View: <% foreach (Customer customerInfo in Model.DataRows) {%> <tr> <td> <%=Html.ActionLink( customerInfo.FullName , ((string)ViewData["ActionNameForSelectedCustomer"]) , JoinParameters(customerInfo.id, (RouteValueDictionary) ViewData["AdditionalSelectionParameters"]) , null)%> </td> <td> <%=customerInfo.LegalGuardianName %> </td> <td> <%=customerInfo.HomePhone %> </td> <td> <%=customerInfo.CellPhone %> </td> </tr> <%}%> Here I'm building simple table that showing customer's details. As you may see, in each row, I'm trying to build a link that will redirect to another action. That action requires customerId and some additional parameters. Additional parameters are different for each page where this partial View is using. So, i decided to make Action methods to pass that additional parameters in the ViewData as RouteValueDictionary instance. Now, on the view i have a problem, i need to pass customerId and that RouteValueDictionary together into Html.ActionLink method. That makes me to figure out some way of how to combine all that params into one object (either object or new RouteValueDictionary instance) Because of the way the MVC does, i can't create create a method in the codebehind class (there is no codebihind in MVC) that will join that parameters. So, i used ugly way - inserted inline code: ...script runat="server"... private RouteValueDictionary JoinParameters(int customerId, RouteValueDictionary defaultValues) { RouteValueDictionary routeValueDictionary = new RouteValueDictionary(defaultValues); routeValueDictionary.Add("customerId", customerId); return routeValueDictionary; } ...script... This way is very ugly for me, because i hate to use inline code in the View part. My question is - is there any better way of how i can mix parameters passed from the action (in ViewData, TempData, other...) and the parameter from the view when building action links. May be i can build this link in other way ? Thanks!

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  • Unable to add item to dataset in Linq to SQL

    - by Mike B
    I am having an issue adding an item to my dataset in Linq to SQL. I am using the exact same method in other tables with no problem. I suspect I know the problem but cannot find an answer (I also suspect all i really need is the right search term for Google). Please keep in mind this is a learning project (Although it is in use in a business) I have posted my code and datacontext below. What I am doing is: Create a view model (Relevant bits are shown) and a simple wpf window that allows editing of 3 properties that are bound to the category object. Category is from the datacontext. Edit works fine but add does not. If I check GetChangeSet() just before the db.submitChanges() call there are no adds, edits or deletes. I suspect an issue with the fact that a Category added without a Subcategory would be an orphan but I cannot seem to find the solution. Command code to open window: CategoryViewModel vm = new CategoryViewModel(); AddEditCategoryWindow window = new AddEditCategoryWindow(vm); window.ShowDialog(); ViewModel relevant stuff: public class CategoryViewModel : ViewModelBase { public Category category { get; set; } // Constructor used to Edit a Category public CategoryViewModel(Int16 categoryID) { db = new OITaskManagerDataContext(); category = QueryCategory(categoryID); } // Constructor used to Add a Category public CategoryViewModel() { db = new OITaskManagerDataContext(); category = new Category(); } } The code for saving changes: // Don't close window unless all controls are validated if (!vm.IsValid(this)) return; var changes = vm.db.GetChangeSet(); // DEBUG try { vm.db.SubmitChanges(ConflictMode.ContinueOnConflict); } catch (ChangeConflictException) { vm.db.ChangeConflicts.ResolveAll(RefreshMode.KeepChanges); vm.db.SubmitChanges(); } The Xaml (Edited fror brevity): <TextBox Text="{Binding category.CatName, Mode=TwoWay, ValidatesOnDataErrors=True, UpdateSourceTrigger=PropertyChanged}" /> <TextBox Text="{Binding category.CatDescription, ValidatesOnDataErrors=True, UpdateSourceTrigger=PropertyChanged}" /> <CheckBox IsChecked="{Binding category.CatIsInactive, Mode=TwoWay}" /> IssCategory in the Issues table is the old, text based category. This field is no longer used and will be removed from the database as soon as this is working and pushed live.

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  • JSON or YAML encoding in GWT/Java on both client and server

    - by KennethJ
    I'm looking for a super simple JSON or YAML library (not particularly bothered which one) written in Java, and can be used in both GWT on the client, and in its original Java form on the server. What I'm trying to do is this: I have my models, which are shared between the client and the server, and these are the primary source of data interchange. I want to design the web service in between to be as simple as possible, and decided to take the RESTful approach. My problem is that I know our application will grow substantially in the future, and writing all the getters, setters, serialization, factories, etc. by hand fills me with absolute dread. So in order to avoid it, I decided to implement annotations to keep track of attributes on the models. The reason I can't just serialize everything directly, using GWT's own one, or one which works through reflection, is because we need a certain amount of logic going on in the serialization process. I.e. whether references to other models get serialized during the serialization of the original model, or whether an ID is just passed, and general simple things like that. I've then written an annotation processor to preprocess my shared models and generate an implementing class with all the getters, setters, serialization, lazy-loading, etc. To make a long story short, I need some type of simple YAML or JSON library, which allows me to encode and decode manually, so I can generate this code through my annotation processor. I have had a look around the interwebs, but every single one I ran into supported some reflection which, while all fine and dandy, make it pretty much useless for GWT. And in the case of GWT's own JSON library, it uses JSNI for speed purposes, making it useless server side. One solution I did think about involved writing writing two sets of serialization methods on the models, one for the client and one for the server, but I'd rather not do that. Also, I'm pretty new to GWT, and even though I have done a lot of Java, it was back in the 1.2 days, so it's a bit rusty. So if you think I'm going about this problem completely the wrong way, I'm open to suggestions.

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  • How can I implement a site with ASP.NET MVC without using Visual Studio?

    - by Cheeso
    I have seen ASP.NET MVC Without Visual Studio, which asks, Is it possible to produce a website based on ASP.NET MVC, without using Visual Studio? And the accepted answer is, yes. Ok, next question: how? Here's an analogy. If I want to create an ASP.NET Webforms page, I load up my favorite text editor, create a file named Something.aspx. Then I insert into that file, some boilerplate: <%@ Page Language="C#" Debug="true" Trace="false" Src="Sourcefile.cs" Inherits="My.Namespace.ContentsPage" %> <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <head> <title>Title goes here </title> <link rel="stylesheet" type="text/css" href="css/style.css"></link> <style type="text/css"> #elementid { font-size: 9pt; color: Navy; ... more css ... } </style> <script type="text/javascript" language='javascript'> // insert javascript here. </script> </head> <body> <asp:Literal Id='Holder' runat='server'/> <br/> <div id='msgs'></div> </body> </html> Then I also create the Sourcefile.cs file: namespace My.Namespace { using System; using System.Web; using System.Xml; // etc... public class ContentsPage : System.Web.UI.Page { protected System.Web.UI.WebControls.Literal Holder; void Page_Load(Object sender, EventArgs e) { // page load logic here } } } And that is a working ASPNET page, created in a text editor. Drop it into an IIS virtual directory, and it's working. What do I have to do, to make a basic, hello, World ASPNET MVC app, in a text editor? (without Visual Studio) Suppose I want a basic MVC app with a controller, one view, and a simple model. What files would I need to create, and what would go into them?

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  • f# types' properties in inconsistent order and of slightly differing types

    - by philbrowndotcom
    I'm trying to iterate through an array of objects and recursively print out each objects properties. Here is my object model: type firmIdentifier = { firmId: int ; firmName: string ; } type authorIdentifier = { authorId: int ; authorName: string ; firm: firmIdentifier ; } type denormalizedSuggestedTradeRecommendations = { id: int ; ticker: string ; direction: string ; author: authorIdentifier ; } Here is how I am instantiating my objects: let getMyIdeasIdeas = [| {id=1; ticker="msfqt"; direction="buy"; author={authorId=0; authorName="john Smith"; firm={firmId=12; firmName="Firm1"}};}; {id=2; ticker="goog"; direction="sell"; author={authorId=1; authorName="Bill Jones"; firm={firmId=13; firmName="ABC Financial"}};}; {id=3; ticker="DFHF"; direction="buy"; author={authorId=2; authorName="Ron James"; firm={firmId=2; firmName="DEFFirm"}};}|] And here is my algorithm to iterate, recurse and print: let rec recurseObj (sb : StringBuilder) o= let props : PropertyInfo [] = o.GetType().GetProperties() sb.Append( o.GetType().ToString()) |> ignore for x in props do let getMethod = x.GetGetMethod() let value = getMethod.Invoke(o, Array.empty) ignore <| match value with | :? float | :? int | :? string | :? bool as f -> sb.Append(x.Name + ": " + f.ToString() + "," ) |> ignore | _ -> recurseObj sb value for x in getMyIdeas do recurseObj sb x sb.Append("\r\n") |> ignore If you couldnt tell, I'm trying to create a csv file and am printing out the types for debugging purposes. The problem is, the first element comes through in the order you'd expect, but all subsequent elements come through with a slightly different (and confusing) ordering of the "child" properties like so: RpcMethods+denormalizedSuggestedTradeRecommendationsid: 1,ticker: msfqt,direction: buy,RpcMethods+authorIdentifierauthorId: 0,authorName: john Smith,RpcMethods+firmIdentifierfirmId: 12,firmName: Firm1, RpcMethods+denormalizedSuggestedTradeRecommendationsid: 2,ticker: goog,direction: sell,RpcMethods+authorIdentifierauthorName: Bill Jones,RpcMethods+firmIdentifierfirmName: ABC Financial,firmId: 13,authorId: 1, RpcMethods+denormalizedSuggestedTradeRecommendationsid: 3,ticker: DFHF,direction: buy,RpcMethods+authorIdentifierauthorName: Ron James,RpcMethods+firmIdentifierfirmName: DEFFirm,firmId: 2,authorId: 2, Any idea what is going on here?

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  • Rails & Twilio: Receiving nil when storing texts received from Twilio

    - by Jon Smooth
    I have set up the request URL in my Twilio account to have it POST to: myurl.com/receivetext. It appears to be successfully posting because when I check the database using the Heroku console I see the following: Post id: 5, body: nil, from: nil, created_at: "2012-06-14 17:28:01", updated_at: "2012-06-14 17:28:01" Why is it receiving nil for the body and from attributes? I can't figure out what I'm doing wrong! The created and updated at are storing successfully but the two attributes that I care about continue to be stored as nil. Here's the Receive Text controller which is receiving the Post request from Twilio: class ReceiveTextController < ApplicationController def index @post=Post.create!(body: params[:Body], from: params[:From]) end end EDIT: When I dump the params I receive the following: "{\"controller\"=\"receive_text\", \"action\"=\"index\"}" I attained this by inserting the following into my ReceiveText controller. @params = Post.create!(body: params.inspect, from: "Dumping Params") and then opening up the Heroku console to find the database entry with from = "Dumping Params". I simulated a Twilio request with a curl with the following command curl -X POST myurl.com/receivetext route -d 'AccountSid=AC123&From=%2B19252411234' I checked the production database again and noticed that the curl request did work when obtaining the FROM atribute. It stored the following: params.inspect returned "{\"AccountSid\"=\"AC123\", \"From\"=\"+19252411234\", \"co..." I received a comment stating: "As long as twilio is hitting the same URL with the same method (GET/POST) it should be filling the params array as well" I have no idea how to make this comment actionable. Any help would be greatly appreciated! I'm very new to rails. Here's my database migration (I have both attributes set to string. I have tried setting it to text and that didn't work either) : class CreatePosts < ActiveRecord::Migration def change create_table :posts do |t| t.string :body t.string :from t.timestamps end end end Here is my Post model: class Post < ActiveRecord::Base attr_accessible :body, :from end Routes (everything appears to be routing just fine) : MovieApp::Application.routes.draw do get "receive_text/index" get "pages/home" get "send_text/send_text_message" root to: 'pages#home' match '/receivetext', to: 'receive_text#index' match '/pages/home', to: 'pages#home' match '/sendtext', to: 'send_text#send_text_message' end Here's my gemfile (incase it helps) source 'https://rubygems.org' gem 'rails', '3.2.3' gem 'badfruit' gem 'twilio-ruby' gem 'logger' gem 'jquery-rails' group :production do gem 'pg' end group :development, :test do gem 'sqlite3' end group :assets do gem 'sass-rails', '~> 3.2.3' gem 'coffee-rails', '~> 3.2.1' gem 'uglifier', '>= 1.0.3' end

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  • CI pagination, POST problem

    - by Gwood
    Okay, I am pretty new in CI and I am stuck on pagination. I am performing this pagination on a record set that is result of a query. Now everything seems to be working fine. But there’s some problem probably with the link. I am displaying 10 results per page. Now if the results are less than 10 then it’s fine. Or If I pull up the entire records in the table it works fine. But in case the result is more than 10 rows, then the first 10 is perfectly displayed, and when I click on the pagination link to get to the next page the next page displays the rest of the results from the query as well as, other records in the table. ??? I am confused.. Any help?? Here’s the model code I am using .... function getTeesLike($field,$param) { $this-db-like($field,$param); $this-db-limit(10, $this-uri-segment(3)); $query=$this-db-get(‘shirt’); if($query-num_rows()0){ return $query-result_array(); } } function getNumTeesfromQ($field,$param) { $this-db-like($field,$param); $query=$this-db-get(‘shirt’); return $query-num_rows(); } And here’s the controller code .... $KW=$this-input-post(‘searchstr’); $this-load-library(‘pagination’); $config[‘base_url’]=‘http://localhost/cit/index.php/tees/show/’; $config[‘total_rows’]=$this-T-getNumTeesfromQ(‘Title’,$KW); $config[‘per_page’]=‘10’; $this-pagination-initialize($config); $data[‘tees’]=$this-T-getTeesLike(‘Title’,$KW); $data[‘title’]=‘Displaying Tees data’; $data[‘header’]=‘Tees List’; $data[‘links’]=$this-pagination-create_links(); $this-load-view(‘tee_res’, $data); //What am I doing wrong here ???? Pls help ... I guess the problem is with the $KW=$this-input-post(‘searchstr’); .. Because if I hard code a value for $KW it works fine. May be I should use POST differently ..but how do I pass the value from the form without POSTING it , its CI so not GET ... ??????

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  • The best way to separate admin functionality from a public site?

    - by AndrewO
    I'm working on a site that's grown both in terms of user-base and functionality to the point where it's becoming evident that some of the admin tasks should be separate from the public website. I was wondering what the best way to do this would be. For example, the site has a large social component to it, and a public sales interface. But at the same time, there's back office tasks, bulk upload processing, dashboards (with long running queries), and customer relations tools in the admin section that I would like to not be effected by spikes in public traffic (or effect the public-facing response time). The site is running on a fairly standard Rails/MySQL/Linux stack, but I think this is more of an architecture problem than an implementation one: mainly, how does one keep the data and business logic in sync between these different applications? Some strategies that I'm evaluating: 1) Create a slave database of the public facing database on another machine. Extract out all of the model and library code so that it can be shared between the applications. Create new controllers and views for the admin interfaces. I have limited experience with replication and am not even sure that it's supposed to be used this way (most of the time I've seen it, it's been for scaling out the read capabilities of the same application, rather than having multiple different ones). I'm also worried about the potential for latency issues if the slave is not on the same network. 2) Create new more task/department-specific applications and use a message oriented middleware to integrate them. I read Enterprise Integration Patterns awhile back and they seemed to advocate this for distributed systems. (Alternatively, in some cases the basic Rails-style RESTful API functionality might suffice.) But, I have nightmares about data synchronization issues and the massive re-architecting that this would entail. 3) Some mixture of the two. For example, the only public information necessary for some of the back office tasks is a read-only completion time or status. Would it make sense to have that on a completely separate system and send the data to public? Meanwhile, the user/group admin functionality would be run on a separate system sharing the database? The downside is, this seems to keep many of the concerns I have with the first two, especially the re-architecting. I'm sure the answers are going to be highly dependent on a site's specific needs, but I'd love to hear success (or failure) stories.

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  • Polymorphic :has_many, :through as module in Rails 3.1 plugin

    - by JohnMetta
    I've search everywhere for a pointer to this, but can't find one. Basically, I want to do what everyone else wants to do when they create a polymorphic relationship in a :has_many, :through way… but I want to do it in a module. I keep getting stuck and think I must be overlooking something simple. To wit: module ActsPermissive module PermissiveUser def self.included(base) base.extend ClassMethods end module ClassMethods def acts_permissive has_many :ownables has_many :owned_circles, :through => :ownables end end end class PermissiveCircle < ActiveRecord::Base belongs_to :ownable, :polymorphic => true end end With a migration that looks like this: create_table :permissive_circles do |t| t.string :ownable_type t.integer :ownable_id t.timestamps end The idea, of course, is that whatever loads acts_permissive will be able to have a list of circles that it owns. For simple tests, I have it "should have a list of circles" do user = Factory :user user.owned_circles.should be_an_instance_of Array end which fails with: Failure/Error: @user.circles.should be_an_instance_of Array NameError: uninitialized constant User::Ownable I've tried: using :class_name => 'ActsPermissive::PermissiveCircle' on the has_many :ownables line, which fails with: Failure/Error: @user.circles.should be_an_instance_of Array ActiveRecord::HasManyThroughSourceAssociationNotFoundError: Could not find the source association(s) :owned_circle or :owned_circles in model ActsPermissive::PermissiveCircle. Try 'has_many :owned_circles, :through => :ownables, :source => <name>'. Is it one of :ownable? while following the suggestion and setting :source => :ownable fails with Failure/Error: @user.circles.should be_an_instance_of Array ActiveRecord::HasManyThroughAssociationPolymorphicSourceError: Cannot have a has_many :through association 'User#owned_circles' on the polymorphic object 'Ownable#ownable' Which seems to suggest that doing things with a non-polymorphic-through is necessary. So I added a circle_owner class similar to the setup here: module ActsPermissive class CircleOwner < ActiveRecord::Base belongs_to :permissive_circle belongs_to :ownable, :polymorphic => true end module PermissiveUser def self.included(base) base.extend ClassMethods end module ClassMethods def acts_permissive has_many :circle_owners, :as => :ownable has_many :circles, :through => :circle_owners, :source => :ownable, :class_name => 'ActsPermissive::PermissiveCircle' end end class PermissiveCircle < ActiveRecord::Base has_many :circle_owners end end With a migration: create_table :permissive_circles do |t| t.string :name t.string :guid t.timestamps end create_table :circle_owner do |t| t.string :ownable_type t.string :ownable_id t.integer :permissive_circle_id end which still fails with: Failure/Error: @user.circles.should be_an_instance_of Array NameError: uninitialized constant User::CircleOwner Which brings us back to the beginning. How can I do what seems to be a rather common polymorphic :has_many, :through on a module? Alternatively, is there a good way to allow an object to be collected by arbitrary objects in a similar way that will work with a module?

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  • How can I modify my classes to use it's collections in WPF TreeView

    - by Victor
    Hello, i'am trying to modify my objects to make hierarchical collection model. I need help. My objects are Good and GoodCategory: public class Good { int _ID; int _GoodCategory; string _GoodtName; public int ID { get { return _ID; } } public int GoodCategory { get { return _GoodCategory; } set { _GoodCategory = value; } } public string GoodName { get { return _GoodName; } set { _GoodName = value; } } public Good(IDataRecord record) { _ID = (int)record["ID"]; _GoodtCategory = (int)record["GoodCategory"]; } } public class GoodCategory { int _ID; string _CategoryName; public int ID { get { return _ID; } } public string CategoryName { get { return _CategoryName; } set { _CategoryName = value; } } public GoodCategory(IDataRecord record) { _ID = (int)record["ID"]; _CategoryName = (string)record["CategoryName"]; } } And I have two Collections of these objects: public class GoodsList : ObservableCollection<Good> { public GoodsList() { string goodQuery = @"SELECT `ID`, `ProductCategory`, `ProductName`, `ProductFullName` FROM `products`;"; using (MySqlConnection conn = ConnectToDatabase.OpenDatabase()) { if (conn != null) { MySqlCommand cmd = conn.CreateCommand(); cmd.CommandText = productQuery; MySqlDataReader rdr = cmd.ExecuteReader(); while (rdr.Read()) { Add(new Good(rdr)); } } } } } public class GoodCategoryList : ObservableCollection<GoodCategory> { public GoodCategoryList () { string goodQuery = @"SELECT `ID`, `CategoryName` FROM `product_categoryes`;"; using (MySqlConnection conn = ConnectToDatabase.OpenDatabase()) { if (conn != null) { MySqlCommand cmd = conn.CreateCommand(); cmd.CommandText = productQuery; MySqlDataReader rdr = cmd.ExecuteReader(); while (rdr.Read()) { Add(new GoodCategory(rdr)); } } } } } So I have two collections which takes data from the database. But I want to use thats collections in the WPF TreeView with HierarchicalDataTemplate. I saw many post's with examples of Hierarlichal Objects, but I steel don't know how to make my objects hierarchicaly. Please help.

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  • Error using Session in IIS

    - by flashnik
    After deployment of my website to IIS I'm getting a following error message when trying to access session: Session state can only be used when enableSessionState is set to true, either in a configuration file or in the Page directive. Please also make sure that System.Web.SessionStateModule or a custom session state module is included in the \\ section in the application configuration. I access it in Page_Load or PreRender events (I tried both versions). With VS Dev Server it works without a problem. I tried both InProc an SessionState storage, 1 and multiple woker processes. I added a enableSessionState = "true" to my webpage explicitly. Here is part of web.config: <system.web> <globalization culture="ru-RU" uiCulture="ru-RU" /> <compilation debug="true" defaultLanguage="c#"> <assemblies> <add assembly="System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" /> <add assembly="System.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" /> <add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /> <add assembly="System.Xml.Linq, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" /> <add assembly="System.Web.Extensions.Design, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /> <add assembly="System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A" /> <add assembly="System.Windows.Forms, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089" /> </assemblies> </compilation> <pages enableEventValidation="false" enableSessionState="true"> <controls> <add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /> <add tagPrefix="asp" namespace="System.Web.UI.WebControls" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /> </controls> </pages> <httpHandlers> <remove verb="*" path="*.asmx" /> <add verb="*" path="*.asmx" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /> <add verb="*" path="*_AppService.axd" validate="false" type="System.Web.Script.Services.ScriptHandlerFactory, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /> <add verb="GET,HEAD" path="ScriptResource.axd" type="System.Web.Handlers.ScriptResourceHandler, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" validate="false" /> </httpHandlers> <httpModules> <add name="ScriptModule" type="System.Web.Handlers.ScriptModule, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" /> <add name="SearchUrlRewriter" type="Synonymizer.SearchUrlRewriter, Synonymizer, Version=1.0.0.0, Culture=neutral" /> <add name="Session" type="System.Web.SessionStateModule" /> </httpModules> <sessionState cookieless="UseCookies" cookieName="My_SessionId" mode="InProc" stateNetworkTimeout="5" /> <customErrors mode="Off" /> </system.web> What else do I need to do to make it work??

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  • Clojure vars and Java static methods

    - by j-g-faustus
    I'm a few days into learning Clojure and are having some teething problems, so I'm asking for advice. I'm trying to store a Java class in a Clojure var and call its static methods, but it doesn't work. Example: user=> (. java.lang.reflect.Modifier isPrivate 1) false user=> (def jmod java.lang.reflect.Modifier) #'user/jmod user=> (. jmod isPrivate 1) java.lang.IllegalArgumentException: No matching method found: isPrivate for class java.lang.Class (NO_SOURCE_FILE:0) at clojure.lang.Compiler.eval(Compiler.java:4543) From the exception it looks like the runtime expects a var to hold an object, so it calls .getClass() to get the class and looks up the method using reflection. In this case the var already holds a class, so .getClass() returns java.lang.Class and the method lookup obviously fails. Is there some way around this, other than writing my own macro? In the general case I'd like to have either an object or a class in a varible and call the appropriate methods on it - duck typing for static methods as well as for instance methods. In this specific case I'd just like a shorter name for java.lang.reflect.Modifier, an alias if you wish. I know about import, but looking for something more general, like the Clojure namespace alias but for Java classes. Are there other mechanisms for doing this? Edit: Maybe I'm just confused about the calling conventions here. I thought the Lisp (and by extension Clojure) model was to evaluate all arguments and call the first element in the list as a function. In this case (= jmod java.lang.reflect.Modifier) returns true, and (.getName jmod) and (.getName java.lang.reflect.Modifier) both return the same string. So the variable and the class name clearly evaluate to the same thing, but they still cannot be called in the same fashion. What's going on here? Edit 2 Answering my second question (what is happening here), the Clojure doc says that If the first operand is a symbol that resolves to a class name, the access is considered to be to a static member of the named class... Otherwise it is presumed to be an instance member http://clojure.org/java_interop under "The Dot special form" "Resolving to a class name" is apparently not the same as "evaluating to something that resolves to a class name", so what I am trying to do here is something the dot special form does not support.

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  • ASP.NET MVC 4/Web API Single Page App for Mobile Devices ... Needs Authentication

    - by lmttag
    We have developed an ASP.NET MVC 4/Web API single page, mobile website (also using jQuery Mobile) that is intended to be accessed only from mobile devices (e.g., iPads, iPhones, Android tables and phones, etc.), not desktop browsers. This mobile website will be hosted internally, like an intranet site. However, since we’re accessing it from mobile devices, we can’t use Windows authentication. We still need to know which user (and their role) is logging in to the mobile website app. We tried simply using ASP.NET’s forms authentication and membership provider, but couldn’t get it working exactly the way we wanted. What we need is for the user to be prompted for a user name and password only on the first time they access the site on their mobile device. After they enter a correct user name and password and have been authenticated once, each subsequent time they access the site they should just go right in. They shouldn’t have to re-enter their credentials (i.e., something needs to be saved locally to each device to identify the user after the first time). This is where we had troubles. Everything worked as expected the first time. That is, the user was prompted to enter a user name and password, and, after doing that, was authenticated and allowed into the site. The problem is every time after the browser was closed on the mobile device, the device and user were not know and the user had to re-enter user name and password. We tried lots of things too. We tried setting persistent cookies in JavaScript. No good. The cookies weren’t there to be read the second time. We tried manually setting persistent cookies from ASP.NET. No good. We, of course, used FormsAuthentication.SetAuthCookie(model.UserName, true); as part of the form authentication framework. No good. We tried using HTML5 local storage. No good. No matter what we tried, if the user was on a mobile device, they would have to log in every single time. (Note: we’ve tried on an iPad and iPhone running both iOS 5.1 and 6.0, with Safari configure to allow cookies, and we’ve tried on Android 2.3.4.) Is there some trick to getting a scenario like this working? Or, do we have to write some sort of custom authentication mechanism? If so, how? And, what? Or, should we use something like claims-based authentication and WIF? Or??? Any help is appreciated. Thanks!

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  • HLSL tex2d sampler seemingly using inconsistent rounding; why?

    - by RJFalconer
    Hello all, I have code that needs to render regions of my object differently depending on their location. I am trying to use a colour map to define these regions. The problem is when I sample from my colour map, I get collisions. Ie, two regions with different colours in the colourmap get the same value returned from the sampler. I've tried various formats of my colour map. I set the colours for each region to be "5" apart in each case; Indexed colour RGB, RGBA: region 1 will have RGB 5%,5%,5%. region 2 will have RGB 10%,10%,10% and so on. HSV Greyscale: region 1 will have HSV 0,0,5%. region 2 will have HSV 0,0,10% and so on. (Values selected in The Gimp) The tex2D sampler returns a value [0..1]. [ I then intend to derive an int array index from region. Code to do with that is unrelated, so has been removed from the question ] float region = tex2D(gColourmapSampler,In.UV).x; Sampling the "5%" colour gave a "region" of 0.05098 in hlsl. From this I assume the 5% represents 5/100*255, or 12.75, which is rounded to 13 when stored in the texture OR when sampled by the sampler; can't tell which. (Reasoning: 0.05098 * 255 ~= 13) By this logic, the 50% should be stored as 127.5. Sampled, I get 0.50196 which implies it was stored as 128. the 70% should be stored as 178.5. Sampled, I get 0.698039, which implies it was stored as 178. What rounding is going on here? (127.5 becomes 128, 178.5 becomes 178 ?!) Edit: OK, http://en.wikipedia.org/wiki/Bankers_rounding#Round_half_to_even Apparently this is "banker's rounding". Is this really what HLSL samplers use? I am using Shader Model 2 and FX Composer. This is my sampler declaration; //Colour map texture gColourmapTexture < string ResourceName = "Globe_Colourmap_Regions_Greyscale.png"; string ResourceType = "2D"; >; sampler2D gColourmapSampler : register(s1) = sampler_state { Texture = <gColourmapTexture>; #if DIRECT3D_VERSION >= 0xa00 Filter = MIN_MAG_MIP_LINEAR; #else /* DIRECT3D_VERSION < 0xa00 */ MinFilter = Linear; MipFilter = Linear; MagFilter = Linear; #endif /* DIRECT3D_VERSION */ AddressU = Clamp; AddressV = Clamp; };

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  • Using pointers, references, handles to generic datatypes, as generic and flexible as possible

    - by Patrick
    In my application I have lots of different data types, e.g. Car, Bicycle, Person, ... (they're actually other data types, but this is just for the example). Since I also have quite some 'generic' code in my application, and the application was originally written in C, pointers to Car, Bicycle, Person, ... are often passed as void-pointers to these generic modules, together with an identification of the type, like this: Car myCar; ShowNiceDialog ((void *)&myCar, DATATYPE_CAR); The 'ShowNiceDialog' method now uses meta-information (functions that map DATATYPE_CAR to interfaces to get the actual data out of Car) to get information of the car, based on the given data type. That way, the generic logic only has to be written once, and not every time again for every new data type. Of course, in C++ you could make this much easier by using a common root class, like this class RootClass { public: string getName() const = 0; }; class Car : public RootClass { ... }; void ShowNiceDialog (RootClass *root); The problem is that in some cases, we don't want to store the data type in a class, but in a totally different format to save memory. In some cases we have hundreds of millions of instances that we need to manage in the application, and we don't want to make a full class for every instance. Suppose we have a data type with 2 characteristics: A quantity (double, 8 bytes) A boolean (1 byte) Although we only need 9 bytes to store this information, putting it in a class means that we need at least 16 bytes (because of the padding), and with the v-pointer we possibly even need 24 bytes. For hundreds of millions of instances, every byte counts (I have a 64-bit variant of the application and in some cases it needs 6 GB of memory). The void-pointer approach has the advantage that we can almost encode anything in a void-pointer and decide how to use it if we want information from it (use it as a real pointer, as an index, ...), but at the cost of type-safety. Templated solutions don't help since the generic logic forms quite a big part of the application, and we don't want to templatize all this. Additionally, the data model can be extended at run time, which also means that templates won't help. Are there better (and type-safer) ways to handle this than a void-pointer? Any references to frameworks, whitepapers, research material regarding this?

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  • Unset/Change Binding in WPF

    - by captcalamares
    How can I unset the binding applied to an object so that I can apply another binding to it from a different location? Suppose I have two data templates binded to the same object reference. Data Template #1 is the default template to be loaded. I try to bind a button command to a Function1 from my DataContext class: <Button Content="Button 1" CommandParameter="{Binding }" Command="{Binding DataContext.Function1, RelativeSource={RelativeSource AncestorType={x:Type Window}}}"/> This actually works and the function gets binded. However, when I try to load Data Template # 2 to the same object (while trying to bind another button command to a different function (Function2) from my DataContext class): <Button Content="Button 2" CommandParameter="{Binding }" Command="{Binding DataContext.Function2, RelativeSource={RelativeSource AncestorType={x:Type Window}}}" /> It doesn't work and the first binding is still the one executed. Is there a workaround to this? EDIT (for better problem context): I defined my templates in my Window.Resources: <Window.Resources> <DataTemplate DataType="{x:Type local:ViewModel1}"> <local:View1 /> </DataTemplate> <DataTemplate DataType="{x:Type local:ViewModel2}"> <local:View2 /> </DataTemplate> </Window.Resources> The View1.xaml and the View2.xaml contain the button definitions that I described above (I want them to command the control of my process flow). ViewModel1 and ViewModel2 are my ViewModels that implement the interface IPageViewModel which is the type of my variable CurrentPageViewModel. In my XAML, I binded ContentControl to the variable CurrentPageViewModel: <ContentControl Content="{Binding CurrentPageViewModel}" HorizontalAlignment="Center"/> In my .CS, I have a list defined as List<IPageViewModel> PageViewModels, which I use to contain the instances of my two View Models: PageViewModels.Add(new ViewModel1()); PageViewModels.Add(new ViewModel2()); // Set starting page CurrentPageViewModel = PageViewModels[0]; When I try to change my CurrentPageViewModel to the other view model, this is when I want the new binding to work. Unfortunately, it doesn't. Am I doing things the right way?

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  • Hibernate3: Self-Referencing Objects

    - by monojohnny
    Need some help on understanding how to do this; I'm going to be running recursive 'find' on a file system and I want to keep the information in a single DB table - with a self-referencing hierarchial structure: This is my DB Table structure I want to populate. DirObject Table: id int NOT NULL, name varchar(255) NOT NULL, parentid int NOT NULL); Here is the proposed Java Class I want to map (Fields only shown): public DirObject { int id; String name; DirObject parent; ... For the 'root' directory was going to use parentid=0; real ids will start at 1, and ideally I want hibernate to autogenerate the ids. Can somebody provide a suggested mapping file for this please; as a secondary question I thought about doing the Java Class like this instead: public DirObject { int id; String name; List<DirObject> subdirs; Could I use the same data model for either of these two methods ? (With a different mapping file of course). --- UPDATE: so I tried the mapping file suggested below (thanks!), repeated here for reference: <hibernate-mapping> <class name="my.proj.DirObject" table="category"> ... <set name="subDirs" lazy="true" inverse="true"> <key column="parentId"/> <one-to-many class="my.proj.DirObject"/> </set> <many-to-one name="parent" class="my.proj.DirObject" column="parentId" cascade="all" /> </class> ...and altered my Java class to have BOTH 'parentid' and 'getSubDirs' [returning a 'HashSet']. This appears to work - thanks, but this is the test code I used to drive this - I think I'm not doing something right here, because I thought Hibernate would take care of saving the subordinate objects in the Set without me having to do this explicitly ? DirObject dirobject=new DirObject(); dirobject.setName("/files"); dirobject.setParent(dirobject); DirObject d1, d2; d1=new DirObject(); d1.setName("subdir1"); d1.setParent(dirobject); d2=new DirObject(); d2.setName("subdir2"); d2.setParent(dirobject); HashSet<DirObject> subdirs=new HashSet<DirObject>(); subdirs.add(d1); subdirs.add(d2); dirobject.setSubdirs(subdirs); session.save(dirobject); session.save(d1); session.save(d2);

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  • Setting up a "to-many" relationship value dependency for a transient Core Data attribute

    - by Greg Combs
    I've got a relatively complicated Core Data relationship structure and I'm trying to figure out how to set up value dependencies (or observations) across various to-many relationships. Let me start out with some basic info. I've got a classroom with students, assignments, and grades (students X assignments). For simplicity's sake, we don't really have to focus much on the assignments yet. StudentObj <--->> ScoreObj <<---> AssignmentObj Each ScoreObj has a to-one relation with the StudentObj and the AssignmentObj. ScoreObj has real attributes for the numerical grade, the turnInDate, and notes. AssignmentObj.scores is the set of Score objects for that assignment (N = all students). AssignmentObj has real attributes for name, dueDate, curveFunction, gradeWeight, and maxPoints. StudentObj.scores is the set of Score objects for that student (N = all assignments). StudentObj also has real attributes like name, studentID, email, etc. StudentObj has a transient (calculated, not stored) attribute called gradeTotal. This last item, gradeTotal, is the real pickle. it calculates the student's overall semester grade using the scores (ScoreObj) from all their assignments, their associated assignment gradeWeights, curves, and maxPoints, and various other things. This gradeTotal value is displayed in a table column, along with all the students and their individual assignment grades. Determining the value of gradeTotal is a relatively expensive operation, particularly with a large class, therefore I want to run it only when necessary. For simplicity's sake, I'm not storing that gradeTotal value in the core data model. I don't mind caching it somewhere, but I'm having a bitch of a time determining where and how to best update that cache. I need to run that calculation for each student whenever any value changes that affects their gradeTotal. If this were a simple to-one relationship, I know I could use something like keyPathsForValuesAffectingGradeTotal ... but it's more like a many-to-one-to-many relationship. Does anyone know of an elegant (and KVC correct) solution? I guess I could tear through all those score and assignment objects and tell them to register their students as observers. But this seems like a blunt force approach.

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  • Parallel programming in C#

    - by Alxandr
    I'm interested in learning about parallel programming in C#.NET (not like everything there is to know, but the basics and maybe some good-practices), therefore I've decided to reprogram an old program of mine which is called ImageSyncer. ImageSyncer is a really simple program, all it does is to scan trough a folder and find all files ending with .jpg, then it calculates the new position of the files based on the date they were taken (parsing of xif-data, or whatever it's called). After a location has been generated the program checks for any existing files at that location, and if one exist it looks at the last write-time of both the file to copy, and the file "in its way". If those are equal the file is skipped. If not a md5 checksum of both files is created and matched. If there is no match the file to be copied is given a new location to be copied to (for instance, if it was to be copied to "C:\test.jpg" it's copied to "C:\test(1).jpg" instead). The result of this operation is populated into a queue of a struct-type that contains two strings, the original file and the position to copy it to. Then that queue is iterated over untill it is empty and the files are copied. In other words there are 4 operations: 1. Scan directory for jpegs 2. Parse files for xif and generate copy-location 3. Check for file existence and if needed generate new path 4. Copy files And so I want to rewrite this program to make it paralell and be able to perform several of the operations at the same time, and I was wondering what the best way to achieve that would be. I've came up with two different models I can think of, but neither one of them might be any good at all. The first one is to parallelize the 4 steps of the old program, so that when step one is to be executed it's done on several threads, and when the entire of step 1 is finished step 2 is began. The other one (which I find more interesting because I have no idea of how to do that) is to create a sort of worker and consumer model, so when a thread is finished with step 1 another one takes over and performs step 2 at that object (or something like that). But as said, I don't know if any of these are any good solutions. Also, I don't know much about parallel programming at all. I know how to make a thread, and how to make it perform a function taking in an object as its only parameter, and I've also used the BackgroundWorker-class on one occasion, but I'm not that familiar with any of them. Any input would be appreciated.

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