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  • Command Design Pattern

    - by pchajer
    After reading command design pattern, I have a couple of question - Why we are creating concrete command and receiver object on client. Can't this initialization on invoker class? I think client should create invoker and pass it's request to invoker. Invoker should take care of all the stuff. By doing this, We have less dependency on client. The design of class diagram is totally different from actual design.

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  • CoreData Model Objects for API

    - by theiOSguy
    I am using CoreData in my application. I want to abstract out all the CoreData related stuff as an API so that the consume can use the API instead of directly using CoreData and its generated model objects. CoreData generates the managed objects model as following @interface Person : NSManagedObject @end I want to define my API for example MyAPI and it has a function called as createPerson:(Person*)p; So the consumer of this createPerson API needs to create a Person data object (like POJO in java world) and invoke this API. But I cannot create Person object using Person *p = [Person alloc] init] because the designated initializer for this Person model created by CoreData does not allow this type of creation. So should I define corresponding user facing data object may be PersonDO and this API should take that instead to carry the data into the API implementation? Is my approach right? Any expert advise if design the API this way is a good design pattern?

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  • What Design Pattern is this?

    - by 01
    I know that everything we do in programming can be described as design pattern(even abstract method has design pattern called template method) public class Guicer extends AbstractModule { private static Injector injector = Guice.createInjector(new Guicer()); public static void setInjector(Injector injector) { Guicer.injector = injector; } public static T getInstance(Class c) { return injector.getInstance(c); } @Override protected void configure() { } } What design patterns are used in this code?

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  • Web applet game design

    - by Vlad
    I making web games in java and having troubles each time when getting to the GUI design, usually I'm looking at others codes and copy most of the design, and I can't decide which design should I use. I used Applet, Canvas, JFrame. What i need is the main loop and draw function that changing between different games. So what class should I use and what design, which is better, why, maybe links to useful tutorials and examples... Please explain. Thanks.

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  • Design cache mechanism

    - by Delashmate
    Hi All, I got assignment to write design for cache mechanism, This is my first time writing a design document, Our program display images for doctors, and we wan't to reduce the parsing time of the images So we want to save the parsed data in advance (in files or inside database) Currently I have several design key ideas Handle locks - each shared data structure should be handled, also files Test - add test to verify the data from the cache is equal to the data from the files To decouple the connection to the database- not to call directly to the database Cleanup mechanisem- to delete old files if the cahce directory exceed configurable threshold Support config file Support performance tool in the feature I will also add class diagram, data flow charts, and workflow What do you think I should add to the key ideas? Do you know good link to atricales about design? Thanks in advance, Dan

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  • Campus Network Design - Firewalls

    - by user3081239
    I am designing a campus network, and the design looks like this: LINX is The London Internet Exchange and JANET is Joint Academic Network. My goal is an almost-fully redundant with high availability, because it will have to support about 15k people, including academic staff, administrative staff and students. I have read some documents in the process , but I am still not sure about some aspects. I want to dedicate this one to firewalls: what are the driving factors in deciding to employ a dedicated firewall, instead of an embedded firewall in the border router? From what I can see, an embedded firewall has these advantages: Easier to maintain Better integration One less hop Less space requirement Cheaper Dedicated firewall has the advantage of being modular. Is there anything else? What am I missing?

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  • Subnetting design for a new building?

    - by Zombie
    A building with 4 floors, each floor is divided as follows; 15 users for accounting, 15 users for finance and 15 users for marketing (i.e 45 user in each floor). Data center is located on the ground floor, with 45 servers to be divided into 15 for all the accounting users in the four floors, another 15 for the finance and the last 15 for the marketing. (i.e each 15 server for each one of the above categories are separated from the other 15 and so on) What is the proper subnetting design for such scenario? Knowing that we are allowed to use anything we want!

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  • Non-English-based programming languages

    - by Jaime Soto
    The University of Antioquia in Colombia teaches its introductory programming courses in Lexico, a Spanish-based, object-oriented .NET language. The intent is to teach programming concepts in the students' native language before introducing English-based mainstream languages. There are many other Non-English-based programming languages and there is even a related question in Stack Overflow. I have several questions regarding these languages: Has anyone on this site learned to program using a non-English-based language? If so, how difficult was the transition to the first English-based language? Is there any research-based evidence that non-English speakers learn programming faster/better using languages with keywords in their native language instead of English-based languages?

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  • XNA 3D model collision is inaccurate

    - by Daniel Lopez
    I am creating a classic game in 3d that deals with asteriods and you have to shoot them and avoid being hit from them. I can generate the asteroids just fine and the ship can shoot bullets just fine. But the asteroids always hit the ship even it doesn't look they are even close. I know 2D collision very well but not 3D so can someone please shed some light to my problem. Thanks in advance. Code For ModelRenderer: using System; using System.Collections.Generic; using System.Linq; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Audio; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.GamerServices; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Input; using Microsoft.Xna.Framework.Media; namespace _3D_Asteroids { class ModelRenderer { private float aspectratio; private Model model; private Vector3 camerapos; private Vector3 modelpos; private Matrix rotationy; float radiansy = 0; private bool isalive; public ModelRenderer(Model m, float AspectRatio, Vector3 initial_pos, Vector3 initialcamerapos) { isalive = true; model = m; if (model.Meshes.Count == 0) { throw new Exception("Invalid model because it contains zero meshes!"); } modelpos = initial_pos; camerapos = initialcamerapos; aspectratio = AspectRatio; return; } public float RadiusOfSphere { get { return model.Meshes[0].BoundingSphere.Radius; } } public BoundingBox BoxBounds { get { return BoundingBox.CreateFromSphere(model.Meshes[0].BoundingSphere); } } public BoundingSphere SphereBounds { get { return model.Meshes[0].BoundingSphere; } } public Vector3 CameraPosition { set { camerapos = value; } get { return camerapos; } } public bool IsAlive { get { return isalive; } } public Vector3 ModelPosition { set { modelpos = value; } get { return modelpos; } } public void RotateY(float radians) { radiansy += radians; rotationy = Matrix.CreateRotationY(radiansy); } public Matrix RotationY { set { rotationy = value; } get { return rotationy; } } public float AspectRatio { set { aspectratio = value; } get { return aspectratio; } } public void Kill() { isalive = false; } public void Draw(float scale) { Matrix world; if (rotationy == new Matrix(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)) { world = Matrix.CreateScale(scale) * Matrix.CreateTranslation(modelpos); } else { world = rotationy * Matrix.CreateScale(scale) * Matrix.CreateTranslation(modelpos); } Matrix view = Matrix.CreateLookAt(camerapos, Vector3.Zero, Vector3.Up); Matrix projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(45.0f), this.AspectRatio, 1f, 100000f); foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.World = world; effect.View = view; effect.Projection = projection; } mesh.Draw(); } } public void Draw() { Matrix world; if (rotationy == new Matrix(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)) { world = Matrix.CreateTranslation(modelpos); } else { world = rotationy * Matrix.CreateTranslation(modelpos); } Matrix view = Matrix.CreateLookAt(camerapos, Vector3.Zero, Vector3.Up); Matrix projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(45.0f), this.AspectRatio, 1f, 100000f); foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.World = world; effect.View = view; effect.Projection = projection; } mesh.Draw(); } } } Code For Game1: using System; using System.Collections.Generic; using System.Linq; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Audio; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.GamerServices; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Input; using Microsoft.Xna.Framework.Media; namespace _3D_Asteroids { /// <summary> /// This is the main type for your game /// </summary> public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; int score = 0, lives = 5; SpriteBatch spriteBatch; GameState gstate = GameState.OnMenuScreen; Menu menu = new Menu(Color.Yellow, Color.White); SpriteFont font; Texture2D background; ModelRenderer ship; Model b, a; List<ModelRenderer> bullets = new List<ModelRenderer>(); List<ModelRenderer> asteriods = new List<ModelRenderer>(); float time = 0.0f; int framecount = 0; SoundEffect effect; public Game1() { graphics = new GraphicsDeviceManager(this); graphics.PreferredBackBufferWidth = 1280; graphics.PreferredBackBufferHeight = 796; graphics.ApplyChanges(); Content.RootDirectory = "Content"; } /// <summary> /// Allows the game to perform any initialization it needs to before starting to run. /// This is where it can query for any required services and load any non-graphic /// related content. Calling base.Initialize will enumerate through any components /// and initialize them as well. /// </summary> protected override void Initialize() { // TODO: Add your initialization logic here base.Initialize(); } /// <summary> /// LoadContent will be called once per game and is the place to load /// all of your content. /// </summary> protected override void LoadContent() { // Create a new SpriteBatch, which can be used to draw textures. spriteBatch = new SpriteBatch(GraphicsDevice); font = Content.Load<SpriteFont>("Fonts\\Lucida Console"); background = Content.Load<Texture2D>("Textures\\B1_stars"); Model p1 = Content.Load<Model>("Models\\p1_wedge"); b = Content.Load<Model>("Models\\pea_proj"); a = Content.Load<Model>("Models\\asteroid1"); effect = Content.Load<SoundEffect>("Audio\\tx0_fire1"); ship = new ModelRenderer(p1, GraphicsDevice.Viewport.AspectRatio, new Vector3(0, 0, 0), new Vector3(0, 0, 9000)); } /// <summary> /// UnloadContent will be called once per game and is the place to unload /// all content. /// </summary> protected override void UnloadContent() { } /// <summary> /// Allows the game to run logic such as updating the world, /// checking for collisions, gathering input, and playing audio. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Update(GameTime gameTime) { KeyboardState state = Keyboard.GetState(PlayerIndex.One); switch (gstate) { case GameState.OnMenuScreen: { if (state.IsKeyDown(Keys.Enter)) { switch (menu.SelectedChoice) { case MenuChoices.Play: { gstate = GameState.GameStarted; break; } case MenuChoices.Exit: { this.Exit(); break; } } } if (state.IsKeyDown(Keys.Down)) { menu.MoveSelectedMenuChoiceDown(gameTime); } else if(state.IsKeyDown(Keys.Up)) { menu.MoveSelectedMenuChoiceUp(gameTime); } else { menu.KeysReleased(); } break; } case GameState.GameStarted: { foreach (ModelRenderer bullet in bullets) { if (bullet.ModelPosition.X < (ship.ModelPosition.X + 4000) && bullet.ModelPosition.Z < (ship.ModelPosition.X + 4000) && bullet.ModelPosition.X > (ship.ModelPosition.Z - 4000) && bullet.ModelPosition.Z > (ship.ModelPosition.Z - 4000)) { bullet.ModelPosition += (bullet.RotationY.Forward * 120); } else if (collidedwithasteriod(bullet)) { bullet.Kill(); } else { bullet.Kill(); } } foreach (ModelRenderer asteroid in asteriods) { if (ship.SphereBounds.Intersects(asteroid.BoxBounds)) { lives -= 1; asteroid.Kill(); // This always hits no matter where the ship goes. } else { asteroid.ModelPosition -= (asteroid.RotationY.Forward * 50); } } for (int index = 0; index < asteriods.Count; index++) { if (asteriods[index].IsAlive == false) { asteriods.RemoveAt(index); } } for (int index = 0; index < bullets.Count; index++) { if (bullets[index].IsAlive == false) { bullets.RemoveAt(index); } } if (state.IsKeyDown(Keys.Left)) { ship.RotateY(0.1f); if (state.IsKeyDown(Keys.Space)) { if (time < 17) { firebullet(); //effect.Play(); } } else { time = 0; } } else if (state.IsKeyDown(Keys.Right)) { ship.RotateY(-0.1f); if (state.IsKeyDown(Keys.Space)) { if (time < 17) { firebullet(); //effect.Play(); } } else { time = 0; } } else if (state.IsKeyDown(Keys.Up)) { ship.ModelPosition += (ship.RotationY.Forward * 50); if (state.IsKeyDown(Keys.Space)) { if (time < 17) { firebullet(); //effect.Play(); } } else { time = 0; } } else if (state.IsKeyDown(Keys.Space)) { time += gameTime.ElapsedGameTime.Milliseconds; if (time < 17) { firebullet(); //effect.Play(); } } else { time = 0.0f; } if ((framecount % 60) == 0) { createasteroid(); framecount = 0; } framecount++; break; } } base.Update(gameTime); } void firebullet() { if (bullets.Count < 3) { ModelRenderer bullet = new ModelRenderer(b, GraphicsDevice.Viewport.AspectRatio, ship.ModelPosition, new Vector3(0, 0, 9000)); bullet.RotationY = ship.RotationY; bullets.Add(bullet); } } void createasteroid() { if (asteriods.Count < 2) { Random random = new Random(); float z = random.Next(-13000, -11000); float x = random.Next(-9000, -8000); Random random2 = new Random(); int degrees = random.Next(0, 45); float radians = MathHelper.ToRadians(degrees); ModelRenderer asteroid = new ModelRenderer(a, GraphicsDevice.Viewport.AspectRatio, new Vector3(x, 0, z), new Vector3(0,0, 9000)); asteroid.RotateY(radians); asteriods.Add(asteroid); } } /// <summary> /// This is called when the game should draw itself. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.CornflowerBlue); switch (gstate) { case GameState.OnMenuScreen: { spriteBatch.Begin(); spriteBatch.Draw(background, Vector2.Zero, Color.White); menu.DrawMenu(ref spriteBatch, font, new Vector2(GraphicsDevice.Viewport.Width / 2, GraphicsDevice.Viewport.Height / 2) - new Vector2(50f), 100f); spriteBatch.End(); break; } case GameState.GameStarted: { spriteBatch.Begin(); spriteBatch.Draw(background, Vector2.Zero, Color.White); spriteBatch.DrawString(font, "Score: " + score.ToString() + "\nLives: " + lives.ToString(), Vector2.Zero, Color.White); spriteBatch.End(); ship.Draw(); foreach (ModelRenderer bullet in bullets) { bullet.Draw(); } foreach (ModelRenderer asteroid in asteriods) { asteroid.Draw(0.1f); } break; } } base.Draw(gameTime); } bool collidedwithasteriod(ModelRenderer bullet) { foreach (ModelRenderer asteroid in asteriods) { if (bullet.SphereBounds.Intersects(asteroid.BoxBounds)) { score += 10; asteroid.Kill(); return true; } } return false; } } } }

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  • design question for transportation agency/workflow system

    - by George2
    I am designing a transportation agency/workflow system, and it including 3 types of people, customer who requests to transport some stuff, drivers who deliver the stuff, and truck manager who manages transport source/destination truck coordination and communicates/organizes drivers. The system is expected to be a web site, and 3 kinds of people could use the web site to submit request, accept request, monitor status of specific stuff transportation, etc. The web site is more like an open agency or a workflow system. I am wondering whether there are any existing technologies, tools or projects (better to be open source, but not a must) which I could build my application faster based on? I prefer to use .Net technologies, but not a must. Thanks in advance!

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  • Domino to Exchange 2007 (or 2010) Design Concerns?

    - by NickToyota
    Today we got the executive green light to proceed with changing from a Domino platform to Exchange. The business prefers Exchange for a messaging platform. (even though IMO IBM Domino is fine - if it aint broke, don't fix it but it was not my call). I have been put in charge of Domino to Exchange process goes smoothly as possible. I have also been told to put together costs for this project. I have some questions and concerns re: network design, licensing, costs: The current setup is as follows. 1 HQ office (100 users), 1 secondary office (50 users), 5 branch offices (under 10 users). 5 different email domains Windows Server 2003 functional level with a few 2008 R2 Servers Lotus Domino Notes Servers (one in each office) Ironmail Appliance Public Domino Web Mail server Majority G5+ Proliant Servers Domino Blackberry Enterprise license and server No VoIP phones What are the basic hardware requirements for Exchange 2007 or 2010? Can I simply purchase a single physical server? Will each office require an Exchange server or possibly additional servers (roles)? How is email routed to the smaller branch offices? Standard or Enterprise licenses? The business has been running Domino (messaging and application services) for over 10 years and also want Exchange to support email services, Blackberry, Outlook Web Access, possibly support for iPhone devices. Thank you Serverfault universe.

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  • Graphic Design in Outlook HTML Emails

    - by PhilPursglove
    At the moment we are creating artwork in Word and saving it as an HTML file. Opening up a new email, clicking insert on menuclicking ‘File’Selecting HTML file and choosing insert as text. The word document is then embedded into the email and we can create HTML links from there. The problem with this method is we are limited to what we can create visually in Word. The artwork just does not look professional enough and we find that sometimes the headers or footers do not appear or do not stay in their correct position. What I would like to do is to be able to start in Adobe InDesign (the graphics package we use). So far I have been able to create artwork in InDesign and create buttons and hyperlinks in InDesignExport it as a pdf, maintaining the hyperlinksSave as HTML documentOpen new emailInsert HTML file choosing insert as text. The problem with this method is that the images move about, the text is all different sizes, but on the plus side, the hyperlinks have been retained. So I am almost there, but not quite. Can anyone suggest what I need to do to get the design to display 'correctly' in Outlook.

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  • Designing a software based load balancer

    - by Kishore pandey
    Hello to all Server fault users, I am new to this website but have constantly been using the mother website, stackover flow. Well to begin with, i would like to design a load balancer for the organization i am working for. As i am very new to this whole, idea about load balancing and networks. I am finding it very difficult to start my project. I did a lot of research on already existing load balancer and found some(HAPROXY,NGINX) that could solve my problems, but the point is, I am still in a dilemma if they could answer the following requirements of mine: The client and server in my architecture are distributed. The load balancer should take care of the firewall. LB server should balance the load among all servers present in WWW cloud. The LB server should have some sort of configuration file, with the help of which it is possible to configure the servers. Heart beat: With the help of which it would be possible to check if any server is down, if any server is down the request should be passed to some other server. Various load balancing algorithms of the incoming requests. Easy error handling. It should be fairly possible to prioritize the incoming requests. Is there any already available load balncer solution on the market that could satisfy these requirements? If not is there any base code available with the help of which i could develop my own load balncer. If not where should i start from scratch? I am practically new to everything. Any help from a load balancer expert is very much appreciated. Thanx a ton in advance. Cheers and regards. Kishore

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  • OpenTK C# Loading Model (3DS?) for display and animation

    - by Randomman159
    For the last few days i have been searching for a model importer that support skeletal movement using OpenTK (C#, OpenGL). I am avoiding writing it myself because firstly i am only just learning OpenGL, but also because i don't see why there's a necessity in recreating the wheel. What do you guys use to import your models? I find it interesting that 90% of OpenTK users will import models for various projects, yet i havn't found a single working importer. Could any of you share your code or point me in the direction of a good loader? 3DS files would be best, but anything that can be exported from an autodesk program would be fine, as long as it uses skeleton animation. Thanks for any help :)

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  • ASP.NET MVC Html.ValidationSummary(true) does not display model errors

    - by msi
    I have some problem with Html.ValidationSummary. I don't want to display property errors in ValidationSummary. And when I set Html.ValidationSummary(true) it does not display error messages from ModelState. When there is some Exception in controller action on string MembersManager.RegisterMember(member); catch section adds an error to the ModelState: ModelState.AddModelError("error", ex.Message); But ValidationSummary does not display this error message. When I set Html.ValidationSummary(false) all messages are displaying, but I don't want to display property errors. How can I fix this problem? Here is the code I'm using: Model: public class Member { [Required(ErrorMessage = "*")] [DisplayName("Login:")] public string Login { get; set; } [Required(ErrorMessage = "*")] [DataType(DataType.Password)] [DisplayName("Password:")] public string Password { get; set; } [Required(ErrorMessage = "*")] [DataType(DataType.Password)] [DisplayName("Confirm Password:")] public string ConfirmPassword { get; set; } } Controller: [HttpPost] public ActionResult Register(Member member) { try { if (!ModelState.IsValid) return View(); MembersManager.RegisterMember(member); } catch (Exception ex) { ModelState.AddModelError("error", ex.Message); return View(member); } } View: <% using (Html.BeginForm("Register", "Members", FormMethod.Post, new { enctype = "multipart/form-data" })) {%> <p> <%= Html.LabelFor(model => model.Login)%> <%= Html.TextBoxFor(model => model.Login)%> <%= Html.ValidationMessageFor(model => model.Login)%> </p> <p> <%= Html.LabelFor(model => model.Password)%> <%= Html.PasswordFor(model => model.Password)%> <%= Html.ValidationMessageFor(model => model.Password)%> </p> <p> <%= Html.LabelFor(model => model.ConfirmPassword)%> <%= Html.PasswordFor(model => model.ConfirmPassword)%> <%= Html.ValidationMessageFor(model => model.ConfirmPassword)%> </p> <div> <input type="submit" value="Create" /> </div> <%= Html.ValidationSummary(true)%> <% } %>

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  • ASP.NET MVC how to bind custom model to view

    - by Smallville
    I would like bind an array data to view in ASP.NET MVC, how can I do that? sorry for not clear about my question. Right now, I creat a custom object(not array), I tried to pass it to View, but the error shows "The model item passed into the dictionary is of type 'ContactView' but this dictionary requires a model item of type 'System.Collections.Generic.IEnumerable"

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  • What is the best database design and/or software to model a thesaurus?

    - by Miles O'Keefe
    I would like to design a web app that functions as a simple thesaurus : a long list of words with attributes, all of which are linked to each other. Wikipedia defines it as: In Information Science, Library Science, and Information Technology, specialized thesauri are designed for information retrieval. They are a type of controlled vocabulary, for indexing or tagging purposes. Such a thesaurus can be used as the basis of an index for online material. The Art and Architecture Thesaurus, for example, is used to index the Canadian Information retrieval thesauri are formally organized so that existing relationships between concepts are made explicit. What database software, design or model would best fit this? Are PHP and MySQL good technologies to handle it?

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  • I keep on getting "save operation failure" after any change on my XCode Data Model

    - by Philip Schoch
    I started using Core Data for iPhone development. I started out by creating a very simple entity (called Evaluation) with just one string property (called evaluationTopic). I had following code for inserting a fresh string: - (void)insertNewObject { // Create a new instance of the entity managed by the fetched results controller. NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; NSEntityDescription *entity = [[fetchedResultsController fetchRequest] entity]; NSManagedObject *newManagedObject = [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context]; // If appropriate, configure the new managed object. [newManagedObject setValue:@"My Repeating String" forKey:@"evaluationTopic"]; // Save the context. NSError *error; if (![context save:&error]) { // Handle the error... } [self.tableView reloadData]; } This worked perfectly fine and by pushing the +button a new "My Repeating String" would be added to the table view and be in persistent store. I then pressed "Design - Add Model Version" in XCode. I added three entities to the existing entity and also added new properties to the existing "Evaluation" entity. Then, I created new files off the entities by pressing "File - New File - Managed Object Classes" and created a new .h and .m file for my four entities, including the "Evaluation" entity with Evaluation.h and Evaluation.m. Now I changed the model version by setting "Design - Data Model - Set Current Version". After having done all this, I changed my insertMethod: - (void)insertNewObject { // Create a new instance of the entity managed by the fetched results controller. NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; NSEntityDescription *entity = [[fetchedResultsController fetchRequest] entity]; Evaluation *evaluation = (Evaluation *) [NSEntityDescription insertNewObjectForEntityForName:[entity name] inManagedObjectContext:context]; // If appropriate, configure the new managed object. [evaluation setValue:@"My even new string" forKey:@"evaluationSpeechTopic"]; // Save the context. NSError *error; if (![context save:&error]) { // Handle the error... } [self.tableView reloadData]; } This does not work though! Every time I want to add a row the simulator crashes and I get the following: "NSInternalInconsistencyException', reason: 'This NSPersistentStoreCoordinator has no persistent stores. It cannot perform a save operation.'" I had this error before I knew about creating new version after changing anything on the datamodel, but why is this still coming up? Do I need to do any mapping (even though I just added entities and properties that did not exist before?). In the Apple Dev tutorial it sounds very easy but I have been struggling with this for long time, never worked after changing model version.

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  • When should I use—and not use—design patterns?

    - by ashmish2
    In a previous question of mine on Stack Overflow, FredOverflow mentioned in the comments: Note that patterns do not magically improve the quality of your code. and Any measure of quality you can imagine. Patterns are not a panacea. I once wrote a Tetris game with about 100 classes that incorporated all the patterns I knew at the time. Why use a simple if/else if you can use a pattern? OO is good, and patterns are even better, right? No, it was a terrible, over-engineered piece of crap. I am quite confused by these comments: I know design patterns help to make code reusable and readable, but when should I use use design patterns and perhaps more importantly, when should I avoid getting carried away with them?

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  • What do you do to get your software design robust, flexible and clear?

    - by Oscar
    I am still getting mature as a software engineering/designer/architect, as you may want to call. At this point in time, I am getting small projects, private projects and so on. What I noticed is that even though I think about the SW structure, design some diagrams, have they really clear in my mind when I start coding, at the end, my software is not flexible and clear as I would like to. I would like to ask you what kind of approaches, mechanisms or even tricks do you use, to get your software (and SW design) flexible, robust and clear (easy to understand and use). So.... Any ideas to give to a beginner?

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  • Entitiy Framework: "Update Database from Model" instead of "Generate Database from Model"

    - by David
    Hey everyone, I have created a Entity Framework 4 model with Visual Studio 2010 and generated a database from it. Now I found myself adding new properties (with default values), changing documentation of columns, changing names of columns, changing types of columns several times. All tasks that do not require much "extra work" in order not to be possible to be achieved automatically (in my humble opinion). Everytime I did "Generate Database from Model" and lost of course the table data. Is there a way just to update the database's architecture so to say - leaving the table data untouched? Maybe with some user interaction especially when changing types etc.? Or would this functionality be simply too difficult to be realized to work in a reliable way? Thanks in advance! Cheers, David

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  • Why is design by contract considered an alternative to the pseudo programming process?

    - by zoopp
    Right now I'm reading Code Complete by Steve McConnell and in chapter 9 he talks about the Pseudo Programming Process (PPP). From what I've understood, the PPP is a way of programming in which the programmer first writes the pseudo code for the routine he's working on, then refines it up to the point where pretty much each pseudo code line can be implemented in 1-3 lines of code, then writes the code in the designated programming language and finally the pseudo code is saved as comments for the purpose of documenting the routine. In chapter 9.4 the author mentions alternatives to the PPP, one of which is 'design by contract'. In design by contract you basically assert preconditions and postconditions of each routine. Now why would that be considered an alternative? To me it seems obvious that I should use both techniques at the same time and not chose one over the other.

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  • Which design better when use foreign key instead of a string to store a list of id

    - by Kien Thanh
    I'm building online examination system. I have designed to table, Question and GeneralExam. The table GeneralExam contains info about the exam like name, description, duration,... Now I would like to design table GeneralQuestion, it will contain the ids of questions belongs to a general exam. Currently, I have two ideas to design GeneralQuestion table: It will have two columns: general_exam_id, question_id. It will have two columns: general_exam_id, list_question_ids (string/text). I would like to know which designing is better, or pros and cons of each designing. I'm using Postgresql database.

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  • What should be the minimal design/scope documentation before development begins?

    - by Oliver Hyde
    I am a junior developer working on my own in the programming aspect of projects. I am given a png file with 5-6 of the pages designed, most times in specific detail. From this I'm asked to develop the back end system needed to maintain the website, usually a cataloging system with products, tags and categories and match the front end to the design. I find myself in a pickle because when I make decisions based on assumptions about the flow of the website, due to a lack of outlining details, I get corrected and am required to rewrite the code to suit what was actually desired. This process happens multiple times throughout a project, often times on the same detail, until it's finally finished, with broken windows all through it. I understand that projects have scope creep, and can appreciate that I need to plan for this, but I feel that in this situation, I'm not receiving enough outlining details to effectively plan for the project, resulting in broken code and a stressed mind. What should be the minimal design/scope documentation I receive before I begin development?

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  • Spring.NET and ADO.NET Entity Data Model

    - by Jason
    Having defined an ADO.NET Entity Data Model, I can then instantiate it in a Repository class to query against the database. using (ApplicationEntities ctx = new ApplicationEntities()) { // query, CRUD, etc } However, that particular line of code becomes boilerplate in most of the methods in the repository class. Is it possible to just use Spring.NET to inject the Entity Data Model, either in the class or, even better, in an abstract parent class that all the repositories inherit from?

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