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• Bullet pattern isn't behaving as expected

  - by Fibericon

  I have a boss that's supposed to continuously shoot five streams of bullets, each at a different angle. It starts off just fine, but doesn't seem to want to use its entire array of bullets. No matter how large I set the length of bulletList, the boss simply stops shooting after a couple of seconds, then pick up again shortly. Here's what I'm using to generate the pattern: Vector3 direction = new Vector3(0.5f, -1, 0); for (int r = 0; r < boss.gun.bulletList.Length; r++) { if (!boss.gun.bulletList[r].isActive) { boss.gun.bulletList[r].direction = direction; boss.gun.bulletList[r].speed = boss.gun.BulletSpeedAdjustment; boss.gun.bulletList[r].position = boss.position; boss.gun.bulletList[r].isActive = true; break; } } direction = new Vector3(-0.5f, -1, 0); //Repeat with four similar for loops, to place a bullet in each direction It doesn't seem to matter if the bulletList length is 1000 or 100000. What could be the issue here?

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• What type of pattern would be used in this case

  - by Admiral Kunkka

  I want to know how to tackle this type of scenario. We are building a person's background, from scratch, and I want to know, conceptually, how to proceed with a secure object pattern in both design and execution... I've been reading on Factory patterns, Model-View-Controller types, Dependency injection, Singleton approaches... and I can't seem to grasp or 'fit' these types of designs decisions into what I'm trying to do.. First and foremost, I started with having a big jack-of-all-trades class, then I read some more, and some tips were to make sure your classes only have a single purpose.. which makes sense and I started breaking down certain things into other classes. Okay, cool. Now I'm looking at dependency injection and kind of didn't really know what's going on. Example/insight of what kind of heirarchy I need to accomplish... class Person needs to access and build from a multitude of different classes. class Culture needs to access a sub-class for culture benefits class Social needs to access class Culture, and other sub-classes class Birth needs to access Social, Culture, and other sub-classes class Childhood/Adolescence/Adulthood need to access everything. Also, depending on different rolls, this class heirarchy needs to create multiple people as well, such as Family, and their backgrounds using some, if not all, of these same classes. Think of it as a people generator, all random, with backgrounds and things that happen to them. Ageing, death of loved ones, military careers, e.t.c. Most of the generation is done randomly, making calls to a mt_rand function to pick from most of the selections inside the classes, guaranteeing the data to be absolutely random. I have most of the bulk-data down, and was looking for some insight from fellow programmers, what do you think?

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• Concurrency pattern of logger in multithreaded application

  - by Dipan Mehta

  The context: We are working on a multi-threaded (Linux-C) application that follows a pipeline model. Each module has a private thread and encapsulated objects which do processing of data; and each stage has a standard form of exchanging data with next unit. The application is free from memory leak and is threadsafe using locks at the point where they exchange data. Total number of threads is about 15- and each thread can have from 1 to 4 objects. Making about 25 - 30 odd objects which all have some critical logging to do. Most discussion I have seen about different levels as in Log4J and it's other translations. The real big questions is about how the overall logging should really happen? One approach is all local logging does fprintf to stderr. The stderr is redirected to some file. This approach is very bad when logs become too big. If all object instantiate their individual loggers - (about 30-40 of them) there will be too many files. And unlike above, one won't have the idea of true order of events. Timestamping is one possibility - but it is still a mess to collate. If there is a single global logger (singleton) pattern - it indirectly blocks so many threads while one is busy putting up logs. This is unacceptable when processing of the threads are heavy. So what should be the ideal way to structure the logging objects? What are some of the best practices in actual large scale applications? I would also love to learn from some of the real designs of large scale applications to get inspirations from!

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• Command Pattern refactor for input processing?

  - by Casey

  According to Game Coding Complete 4th. ed. processing input via the following is considered unmanagable and inflexible. But does not show an example. I've used the Command pattern to represent GUI button commands but could not figure out how to represent the input from the keyboard and/or mouse. if(g_keyboard->KeyDown(KEY_ESC)) { quit = true; return; } //Processing if(g_keyboard->KeyDown(KEY_T)) { g_show_test_gateway = !g_show_test_gateway; } if(g_mouse->ButtonDown(a2de::Mouse::BUTTON2)) { g_selected_part = GWPart::PART_NONE; SetMouseImageToPartImage(); } ResetButtonStates(); g_prevButton = g_curButton; g_curButton = GetButtonHovered(); if(g_curButton) { g_mouse->SetImageToDefault(); if(g_mouse->ButtonDown(a2de::Mouse::BUTTON1) || g_mouse->ButtonPress(a2de::Mouse::BUTTON1)) { ButtonPressCommand curCommand(g_curButton); curCommand.Execute(); } else if(g_mouse->ButtonUp(a2de::Mouse::BUTTON1)) { if(g_prevButton == g_curButton) { ButtonReleaseCommand curCommand(g_curButton); curCommand.Execute(); if(g_curButton->GetType() == "export") { ExportCommand curCommand(g_curButton, *g_gateway); curCommand.Execute(); } } else { ResetButtonStates(); } } else { ButtonHoverCommand curCommand(g_curButton); curCommand.Execute(); } } else { g_status_message.clear(); SetMouseImageToPartImage(); if(g_mouse->ButtonDown(a2de::Mouse::BUTTON1)) { CreatePartCommand curCommand(*g_gateway, g_selected_part, a2de::Vector2D(g_mouse->GetX(), g_mouse->GetY())); curCommand.Execute(); } }

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• What Pattern will solve this - fetching dependent record from database

  - by tunmise fasipe

  I have these classes class Match { int MatchID, int TeamID, //used to reference Team ... other fields } Note: Match actually have 2 teams which means 2 TeamID class Team { int TeamID, string TeamName } In my view I need to display List<Match> showing the TeamName. So I added another field class Match { int MatchID, int TeamID, //used to reference Team ... other fields string TeamName; } I can now do Match m = getMatch(id); m.TeamName = getTeamName(m.TeamId); //get name from database But for a List<Match>, getTeamName(TeamId) will go to the database to fetch TeamName for each TeamID. For a page of 10 Matches per page, that could be (10x2Teams)=20 trip to database. To avoid this, I had the idea of loading everything once, store it in memory and only lookup the TeamName in memory. This made me have a rethink that what if the records are 5000 or more. What pattern is used to solve this and how?

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• MVVM and service pattern

  - by alfa-alfa

  I'm building a WPF application using the MVVM pattern. Right now, my viewmodels calls the service layer to retrieve models (how is not relevant to the viewmodel) and convert them to viewmodels. I'm using constructor injection to pass the service required to the viewmodel. It's easily testable and works well for viewmodels with few dependencies, but as soon as I try to create viewModels for complex models, I have a constructor with a LOT of services injected in it (one to retrieve each dependencies and a list of all available values to bind to an itemsSource for example). I'm wondering how to handle multiple services like that and still have a viewmodel that I can unit test easily. I'm thinking of a few solutions: Creating a services singleton (IServices) containing all the available services as interfaces. Example: Services.Current.XXXService.Retrieve(), Services.Current.YYYService.Retrieve(). That way, I don't have a huge constructor with a ton of services parameters in them. Creating a facade for the services used by the viewModel and passing this object in the ctor of my viewmodel. But then, I'll have to create a facade for each of my complexe viewmodels, and it might be a bit much... What do you think is the "right" way to implement this kind of architecture ?

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• Design pattern to handle queries using multiple models

  - by coderkane

  I am presented with a dilemma while trying to re-designing the class structure for my PHP/MySQL application to make it more elegant and conform it to the SOLID principle. The problem goes like this: Let as assume, there is an abstract class called person which has certain properties to define a generic person, such as name, age, date of birth etc. There are two classes, student, and teacher, that implements this abstract class. They add their own unique properties to it. I have designed all the three classes to include all the operational logic (details of which are not relevant in context of the question). Now, I need to create views/reports/data grids which contain details from multiple classes, for example, say, a list of all students doing projects in Chemistry mentored by a teacher whose name is the parameter to the query. This is just one example of a view, there are many different views in the application, which uses data from 3-4 tables, and each of them have multiple input parameters to generate them. Considering this particular example, I have written the relevant query using JOIN and the results are as expected and proper, now here is the dilemma: Keeping in mind the single responsibility principle, where should I keep this query? It does not belong to either Student class, or Teacher class or any other classes currently present. a) Should I create a new class, say dataView class, and design it as a MVC pattern and keep the query there? What about the other views? how do they fit in this architecture? b) Should I not keep the query in code at all, and make it DB View ? c) Am I completely wrong in the approach? If so what is the right approach? My considerations are as follows: a) should be easy to add new views later on if requirement comes, without having to copy-paste-modify code b) would like to make it as loosely coupled as possible so that if minor db structure changes happen, it does not break I did google searches on report design and OOP report generators, but all the result seem to focus on the visual design of the report rather than fetching the data. I have already taken care of the visual aspect of the report using MVC with html templates. I am sure this is a very fundamental problem with known solution, but I am somehow not able to find it (maybe searching with wrong keyword). Edit1: Modified the title to make it more relevant Edit2: The accepted answer got me thinking in the right direction and identify my design flaws, which eventually led me to find this question and the solution in Stack Overflow which gave me the detailed answer to clear the confusion.

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• Validation and Error Generation when using the Data Mapper Pattern

  - by AndyPerlitch

  I am working on saving state of an object to a database using the data mapper pattern, but I am looking for suggestions/guidance on the validation and error message generation step (step 4 below). Here are the general steps as I see them for doing this: (1) The data mapper is used to get current info (assoc array) about the object in db: +=====================================================+ | person_id | name | favorite_color | age | +=====================================================+ | 1 | Andy | Green | 24 | +-----------------------------------------------------+ mapper returns associative array, eg. Person_Mapper::getPersonById($id) : $person_row = array( 'person_id' => 1, 'name' => 'Andy', 'favorite_color' => 'Green', 'age' => '24', ); (2) the Person object constructor takes this array as an argument, populating its fields. class Person { protected $person_id; protected $name; protected $favorite_color; protected $age; function __construct(array $person_row) { $this->person_id = $person_row['person_id']; $this->name = $person_row['name']; $this->favorite_color = $person_row['favorite_color']; $this->age = $person_row['age']; } // getters and setters... public function toArray() { return array( 'person_id' => $this->person_id, 'name' => $this->name, 'favorite_color' => $this->favorite_color, 'age' => $this->age, ); } } (3a) (GET request) Inputs of an HTML form that is used to change info about the person is populated using Person::getters <form> <input type="text" name="name" value="<?=$person->getName()?>" /> <input type="text" name="favorite_color" value="<?=$person->getFavColor()?>" /> <input type="text" name="age" value="<?=$person->getAge()?>" /> </form> (3b) (POST request) Person object is altered with the POST data using Person::setters $person->setName($_POST['name']); $person->setFavColor($_POST['favorite_color']); $person->setAge($_POST['age']); *(4) Validation and error message generation on a per-field basis - Should this take place in the person object or the person mapper object? - Should data be validated BEFORE being placed into fields of the person object? (5) Data mapper saves the person object (updates row in the database): $person_mapper->savePerson($person); // the savePerson method uses $person->toArray() // to get data in a more digestible format for the // db gateway used by person_mapper Any guidance, suggestions, criticism, or name-calling would be greatly appreciated.

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• How pattern lock disbles screen lock in android

  - by CED

  Hi, In android 2.1, if we enable pattern lock, then the screen lock (slide to unlock) is not displayed and if pattern lock is disabled then screen lock is enabled again. Can someone point me out the java file in framework and the function where this happens. I mean when the screen is about to get locked, how does android decide that whether it will display pattern lock or screen lock and if pattern lock, how it prevents the screen lock from getting displayed.

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• Design pattern for adding / removing elements

  - by de3

  Wikipedia's definition for Iterator pattern design: the Iterator pattern is a design pattern in which iterators are used to access the elements of an aggregate object sequentially without exposing its underlying implementation. Iterator interface in java provides the following methods hasNext() next() remove() Is there a pattern design, or a java interface for inserting / deleting elements, and getting length of the aggregate object, in addition to iterating them? I know remove() is an optional method that can be used once per call to next(), but I am implementing a circular FIFO array and need a method delete() independent of iterator's next().

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• WCF Rest services for use with the repository pattern?

  - by mark smith

  Hi there, I am considering moving my Service Layer and my data layer (repository pattern) to a WCF Rest service. So basically i would have my software installed locally (WPF client) which would call the Service Layer that exists via a Rest Service... The service layer would then call my data layer using a WCF Rest Service also OR maybe just call it via the DLL assembly I was hoping to understand what the performance would be like. Currently I have my datalayer and servicelayer installed locally via DLL Assemblies locally on the pc. Also i presume the WCF REST services won't support method overloading hance the same name but with a different signature?? I would really appreciate any feedback anyone can give. Thanks

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• Best Design Pattern for Coupling User Interface Components and Data Structures

  - by szahn

  I have a windows desktop application with a tree view. Due to lack of a sound data-binding solution for a tree view, I've implemented my own layer of abstraction on it to bind nodes to my own data structure. The requirements are as follows: Populate a tree view with nodes that resemble fields in a data structure. When a node is clicked, display the appropriate control to modify the value of that property in the instance of the data structure. The tree view is populated with instances of custom TreeNode classes that inherit from TreeNode. The responsibility of each custom TreeNode class is to (1) format the node text to represent the name and value of the associated field in my data structure, (2) return the control used to modify the property value, (3) get the value of the field in the control (3) set the field's value from the control. My custom TreeNode implementation has a property called "Control" which retrieves the proper custom control in the form of the base control. The control instance is stored in the custom node and instantiated upon first retrieval. So each, custom node has an associated custom control which extends a base abstract control class. Example TreeNode implementation: //The Tree Node Base Class public abstract class TreeViewNodeBase : TreeNode { public abstract CustomControlBase Control { get; } public TreeViewNodeBase(ExtractionField field) { UpdateControl(field); } public virtual void UpdateControl(ExtractionField field) { Control.UpdateControl(field); UpdateCaption(FormatValueForCaption()); } public virtual void SaveChanges(ExtractionField field) { Control.SaveChanges(field); UpdateCaption(FormatValueForCaption()); } public virtual string FormatValueForCaption() { return Control.FormatValueForCaption(); } public virtual void UpdateCaption(string newValue) { this.Text = Caption; this.LongText = newValue; } } //The tree node implementation class public class ExtractionTypeNode : TreeViewNodeBase { private CustomDropDownControl control; public override CustomControlBase Control { get { if (control == null) { control = new CustomDropDownControl(); control.label1.Text = Caption; control.comboBox1.Items.Clear(); control.comboBox1.Items.AddRange( Enum.GetNames( typeof(ExtractionField.ExtractionType))); } return control; } } public ExtractionTypeNode(ExtractionField field) : base(field) { } } //The custom control base class public abstract class CustomControlBase : UserControl { public abstract void UpdateControl(ExtractionField field); public abstract void SaveChanges(ExtractionField field); public abstract string FormatValueForCaption(); } //The custom control generic implementation (view) public partial class CustomDropDownControl : CustomControlBase { public CustomDropDownControl() { InitializeComponent(); } public override void UpdateControl(ExtractionField field) { //Nothing to do here } public override void SaveChanges(ExtractionField field) { //Nothing to do here } public override string FormatValueForCaption() { //Nothing to do here return string.Empty; } } //The custom control specific implementation public class FieldExtractionTypeControl : CustomDropDownControl { public override void UpdateControl(ExtractionField field) { comboBox1.SelectedIndex = comboBox1.FindStringExact(field.Extraction.ToString()); } public override void SaveChanges(ExtractionField field) { field.Extraction = (ExtractionField.ExtractionType) Enum.Parse(typeof(ExtractionField.ExtractionType), comboBox1.SelectedItem.ToString()); } public override string FormatValueForCaption() { return string.Empty; } The problem is that I have "generic" controls which inherit from CustomControlBase. These are just "views" with no logic. Then I have specific controls that inherit from the generic controls. I don't have any functions or business logic in the generic controls because the specific controls should govern how data is associated with the data structure. What is the best design pattern for this?

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• Design pattern for logging changes in parent/child objects saved to database

  - by andrew

  I’ve got a 2 database tables in parent/child relationship as one-many. I’ve got three classes representing the data in these two tables: Parent Class { Public int ID {get; set;} .. other properties } Child Class { Public int ID {get;set;} Public int ParentID {get; set;} .. other properties } TogetherClass { Public Parent Parent; Public List<Child> ChildList; } Lastly I’ve got a client and server application – I’m in control of both ends so can make changes to both programs as I need to. Client makes a request for ParentID and receives a Together Class for the matching parent, and all of the child records. The client app may make changes to the children – add new children, remove or modify existing ones. Client app then sends the Together Class back to the server app. Server app needs to update the parent and child records in the database. In addition I would like to be able to log the changes – I’m doing this by having 2 separate tables one for Parent, one for child; each containing the same columns as the original plus date time modified, by whom and a list of the changes. I’m unsure as to the best approach to detect the changes in records – new records, records to be deleted, records with no fields changed, records with some fields changed. I figure I need to read the parent & children records and compare those to the ones in the Together Class. Strategy A: If Together class’s child record has an ID of say 0, that indicates a new record; insert. Any deleted child records are no longer in the Together Class; see if any of the comparison child records are not found in the Together class and delete if not found (Compare using ID). Check each child record for changes and if changed log. Strategy B: Make a new Updated TogetherClass UpdatedClass { Public Parent Parent {get; set} Public List<Child> ListNewChild {get;set;} Public List<Child> DeletedChild {get;set;} Public List<Child> ExistingChild {get;set;} // used for no changes and modified rows } And then process as per the list. The reason why I’m asking for ideas is that both of these solutions don’t seem optimal to me and I suspect this problem has been solved already – some kind of design pattern ? I am aware of one potential problem in this general approach – that where Client App A requests a record; App B requests same record; A then saves changes; B then saves changes which may overwrite changes A made. This is a separate locking issue which I’ll raise a separate question for if I’ve got trouble implementing. The actual implementation is c#, SQL Server and WCF between client and server - sharing a library containing the class implementations. Apologies if this is a duplicate post – I tried searching various terms without finding a match though.

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• Why has the accessor methods from the JavaBean specification become the standard for Java development?

  - by Dakotah North

  The JavaBeans Specification describes a JavaBean as A Java Bean is a reusable software component that can be manipulated visually in a builder tool Since the majority of the lines of code that are written seem to have nothing to do with being manipulated visually in a builder tool, why has the JavaBean specification been the "way" to write object oriented code? I would like to forgo the traditional getter/setter in favor of Fluent Interfaces all throughout the code, not just in builders but fear doing so since this is traditionally not the way way object oriented code is written in Java.

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• A column ID occurred more than once in the specification

  - by Puzzle84

  Recently i've picked up my EF 4.1 / MVC 3 project again and started building in actual frontend capabilities. Now i'm developing a "simple" message system but upon going to that page i get the error as stated in the title EDIT It creates the database just not the models. Stack trace: [NullReferenceException: Object reference not set to an instance of an object.] ASP._Page_Views_Inbox_Index_cshtml.Execute() in c:\Development\MVC\DOCCL\Views\Inbox\Index.cshtml:18 System.Web.WebPages.WebPageBase.ExecutePageHierarchy() +197 System.Web.Mvc.WebViewPage.ExecutePageHierarchy() +81 System.Web.WebPages.StartPage.RunPage() +17 System.Web.WebPages.StartPage.ExecutePageHierarchy() +62 System.Web.WebPages.WebPageBase.ExecutePageHierarchy(WebPageContext pageContext, TextWriter writer, WebPageRenderingBase startPage) +76 System.Web.Mvc.RazorView.RenderView(ViewContext viewContext, TextWriter writer, Object instance) +222 System.Web.Mvc.BuildManagerCompiledView.Render(ViewContext viewContext, TextWriter writer) +115 System.Web.Mvc.ViewResultBase.ExecuteResult(ControllerContext context) +295 System.Web.Mvc.ControllerActionInvoker.InvokeActionResult(ControllerContext controllerContext, ActionResult actionResult) +13 System.Web.Mvc.<c_DisplayClass1c.b_19() +23 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultFilter(IResultFilter filter, ResultExecutingContext preContext, Func1 continuation) +242 System.Web.Mvc.<>c__DisplayClass1e.<InvokeActionResultWithFilters>b__1b() +21 System.Web.Mvc.ControllerActionInvoker.InvokeActionResultWithFilters(ControllerContext controllerContext, IList1 filters, ActionResult actionResult) +177 System.Web.Mvc.ControllerActionInvoker.InvokeAction(ControllerContext controllerContext, String actionName) +324 System.Web.Mvc.Controller.ExecuteCore() +106 System.Web.Mvc.ControllerBase.Execute(RequestContext requestContext) +91 System.Web.Mvc.ControllerBase.System.Web.Mvc.IController.Execute(RequestContext requestContext) +10 System.Web.Mvc.<c_DisplayClassb.b_5() +34 System.Web.Mvc.Async.<c_DisplayClass1.b_0() +19 System.Web.Mvc.Async.<c_DisplayClass81.<BeginSynchronous>b__7(IAsyncResult _) +10 System.Web.Mvc.Async.WrappedAsyncResult1.End() +62 System.Web.Mvc.<c_DisplayClasse.b_d() +48 System.Web.Mvc.SecurityUtil.b_0(Action f) +7 System.Web.Mvc.SecurityUtil.ProcessInApplicationTrust(Action action) +22 System.Web.Mvc.MvcHandler.EndProcessRequest(IAsyncResult asyncResult) +60 System.Web.Mvc.MvcHandler.System.Web.IHttpAsyncHandler.EndProcessRequest(IAsyncResult result) +9 System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +9478661 System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +178 InnerException : {"A column ID occurred more than once in the specification."} The recently added code is. Controller: // // GET: /Inbox/Index/5/1 public ActionResult Index(int? Id, int Page = 1) { try { const int pageSize = 10; var messages = from m in horseTracker.Messages where m.ReceiverId.Equals(Id) select m; var paginatedMessages = new PaginatedList<Message>(messages, Page, pageSize); return View(paginatedMessages); } catch (Exception ex) { } return View(); } Models public class Message { [Key] public int Id { get; set; } [Required(ErrorMessage = "Subject is required")] [Display(Name = "Subject")] public string Subject { get; set; } [Required(ErrorMessage = "Message is required")] [Display(Name = "Message")] public string Content { get; set; } [Required] [Display(Name = "Date")] public DateTime Created { get; set; } public Boolean Read { get; set; } [Required(ErrorMessage = "Can't create a message without a user")] public int SenderId { get; set; } public virtual User Sender { get; set; } [Required(ErrorMessage = "Please pick a recipient")] public int ReceiverId { get; set; } public virtual User Receiver { get; set; } } public class User { [Key] public int Id { get; set; } [Required] [Display(Name = "Username")] public string UserName { get; set; } [Required] [Display(Name = "First Name")] public string FirstName { get; set; } [Required] [Display(Name = "Last Name")] public string LastName { get; set; } [Required] [Display(Name = "E-Mail")] public string Email { get; set; } [Required] [Display(Name = "Password")] public string Password { get; set; } [Required] [Display(Name = "Country")] public string Country { get; set; } public string EMail { get; set; } //Races public virtual ICollection<Message> Messages { get; set; } } modelBuilder.Entity<User>() .HasMany(u => u.Messages) .WithRequired(m => m.Receiver) .HasForeignKey(m => m.ReceiverId) .WillCascadeOnDelete(false); Anyone have a clue on why i might be getting that error? Before i added these classes it was working fine.

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• Design Pattern for Complex Data Modeling

  - by Aaron Hayman

  I'm developing a program that has a SQL database as a backing store. As a very broad description, the program itself allows a user to generate records in any number of user-defined tables and make connections between them. As for specs: Any record generated must be able to be connected to any other record in any other user table (excluding itself...the record, not the table). These "connections" are directional, and the list of connections a record has is user ordered. Moreover, a record must "know" of connections made from it to others as well as connections made to it from others. The connections are kind of the point of this program, so there is a strong possibility that the number of connections made is very high, especially if the user is using the software as intended. A record's field can also include aggregate information from it's connections (like obtaining average, sum, etc) that must be updated on change from another record it's connected to. To conserve memory, only relevant information must be loaded at any one time (can't load the entire database in memory at load and go from there). I cannot assume the backing store is local. Right now it is, but eventually this program will include syncing to a remote db. Neither the user tables, connections or records are known at design time as they are user generated. I've spent a lot of time trying to figure out how to design the backing store and the object model to best fit these specs. In my first design attempt on this, I had one object managing all a table's records and connections. I attempted this first because it kept the memory footprint smaller (records and connections were simple dicts), but maintaining aggregate and link information between tables became....onerous (ie...a huge spaghettified mess). Tracing dependencies using this method almost became impossible. Instead, I've settled on a distributed graph model where each record and connection is 'aware' of what's around it by managing it own data and connections to other records. Doing this increases my memory footprint but also let me create a faulting system so connections/records aren't loaded into memory until they're needed. It's also much easier to code: trace dependencies, eliminate cycling recursive updates, etc. My biggest problem is storing/loading the connections. I'm not happy with any of my current solutions/ideas so I wanted to ask and see if anybody else has any ideas of how this should be structured. Connections are fairly simple. They contain: fromRecordID, fromTableID, fromRecordOrder, toRecordID, toTableID, toRecordOrder. Here's what I've come up with so far: Store all the connections in one big table. If I do this, either I load all connections at once (one big db call) or make a call every time a user table is loaded. The big issue here: the size of the connections table has the potential to be huge, and I'm afraid it would slow things down. Store in separate tables all the outgoing connections for each user table. This is probably the worst idea I've had. Now my connections are 'spread out' over multiple tables (one for each user table), which means I have to make a separate DB called to each table (or make a huge join) just to find all the incoming connections for a particular user table. I've avoided making "one big ass table", but I'm not sure the cost is worth it. Store in separate tables all outgoing AND incoming connections for each user table (using a flag to distinguish between incoming vs outgoing). This is the idea I'm leaning towards, but it will essentially double the total DB storage for all the connections (as each connection will be stored in two tables). It also means I have to make sure connection information is kept in sync in both places. This is obviously not ideal but it does mean that when I load a user table, I only need to load one 'connection' table and have all the information I need. This also presents a separate problem, that of connection object creation. Since each user table has a list of all connections, there are two opportunities for a connection object to be made. However, connections objects (designed to facilitate communication between records) should only be created once. This means I'll have to devise a common caching/factory object to make sure only one connection object is made per connection. Does anybody have any ideas of a better way to do this? Once I've committed to a particular design pattern I'm pretty much stuck with it, so I want to make sure I've come up with the best one possible.

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• Design Patterns for Coordinating Change Event Listeners

  - by mkraken

  I've been working with the Observer pattern in JavaScript using various popular libraries for a number of years (YUI & jQuery). It's often that I need to observe a set of property value changes (e.g. respond only when 2 or more specific values change). Is there a elegant way to 'subscribe' the handler so that it is only called one time? Is there something I'm missing or doing wrong in my design?

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• How to properly implement the Strategy pattern in a web MVC framework?

  - by jboxer

  In my Django app, I have a model (lets call it Foo) with a field called "type". I'd like to use Foo.type to indicate what type the specific instance of Foo is (possible choices are "Number", "Date", "Single Line of Text", "Multiple Lines of Text", and a few others). There are two things I'd like the "type" field to end up affecting; the way a value is converted from its normal type to text (for example, in "Date", it may be str(the_date.isoformat())), and the way a value is converted from text to the specified type (in "Date", it may be datetime.date.fromtimestamp(the_text)). To me, this seems like the Strategy pattern (I may be completely wrong, and feel free to correct me if I am). My question is, what's the proper way to code this in a web MVC framework? In a client-side app, I'd create a Type class with abstract methods "serialize()" and "unserialize()", override those methods in subclasses of Type (such as NumberType and DateType), and dynamically set the "type" field of a newly-instantiated Foo to the appropriate Type subclass at runtime. In a web framework, it's not quite as straightforward for me. Right now, the way that makes the most sense is to define Foo.type as a Small Integer field and define a limited set of choices (0 = "Number", 1 = "Date", 2 = "Single Line of Text", etc.) in the code. Then, when a Foo object is instantiated, use a Factory method to look at the value of the instance's "type" field and plug in the correct Type subclass (as described in the paragraph above). Foo would also have serialize() and unserialize() methods, which would delegate directly to the plugged-in Type subclass. How does this design sound? I've never run into this issue before, so I'd really like to know if other people have, and how they've solved it.

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• How to efficiently implement a strategy pattern with spring ?

  - by Anth0

  I have a web application developped in J2EE 1.5 with Spring framework. Application contains "dashboards" which are simple pages where a bunch of information are regrouped and where user can modify some status. Managers want me to add a logging system in database for three of theses dashboards. Each dashboard has different information but the log should be traced by date and user's login. What I'd like to do is to implement the Strategy pattern kind of like this : interface DashboardLog { void createLog(String login, Date now); } // Implementation for one dashboard class PrintDashboardLog implements DashboardLog { Integer docId; String status; void createLog(String login, Date now){ // Some code } } class DashboardsManager { DashboardLog logger; String login; Date now; void createLog(){ logger.log(login,now); } } class UpdateDocAction{ DashboardsManager dbManager; void updateSomeField(){ // Some action // Now it's time to log dbManagers.setLogger = new PrintDashboardLog(docId, status); dbManagers.createLog(); } } Is it "correct" (good practice, performance, ...) to do it this way ? Is there a better way ? Note :I did not write basic stuff like constructors and getter/setter.

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• How to recall search pattern when writing replace regex pattern in Vim?

  - by Tom Morris

  Here's the scenario: I've got a big file filled with all sorts of eclectic rubbish that I want to regex. I fiddle around and come up with a perfect search pattern by using the / command and seeing what it highlights. Now I want to use that pattern to replace with. So, I start typing :%s/ and I cannot recall what the pattern was. Is there some magical keyboard command that will pull in my last search pattern here? If I'm writing a particularly complex regex, I have even opened up a new MacVim window, typed the regex from the first window into a buffer there, then typed it back into the Vim window when writing the replace pattern. There has got to be a better way of doing so.

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• CSS repeat pattern with linear gradient

  - by luca

  I'm on my first approach with photoshop patterns.I'm buildin a webpage where I want to use my pattern to give a nice effect to my webpage background. The pattern I found is 120x120 px If I was done here I should use this css: background-imag:url(mypattern.jpg); background-repeat:repeat; But Im not done.Id like to *add to my page's background a linear gradient(dir=top/down col=light-blue/green) with the pattern fill layer on top of it, with blending mode=darken *. This is the final effect: I come to the point. QUESTION: Combining linear vertical-gradient effect and my 120x120 pattern is it possible to find a pattern that I could use to repeat itself endlessly both vertical and horizontal??which is a common solution in this case? Hope It's clear thanks Luca

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• PHP preg_replace() pattern, string sanitization.

  - by Otar

  I have a regex email pattern and would like to strip all but pattern-matched characters from the string, in a short I want to sanitize string... I'm not a regex guru, so what I'm missing in regex? <?php $pattern = "/^([\w\!\#$\%\&\'\*\+\-\/\=\?\^\`{\|\}\~]+\.)*[\w\!\#$\%\&\'\*\+\-\/\=\?\^\`{\|\}\~]+@((((([a-z0-9]{1}[a-z0-9\-]{0,62}[a-z0-9]{1})|[a-z])\.)+[a-z]{2,6})|(\d{1,3}\.){3}\d{1,3}(\:\d{1,5})?)$/i"; $email = 'contact<>@domain.com'; // wrong email $sanitized_email = preg_replace($pattern, NULL, $email); echo $sanitized_email; // Should be [email protected] ?> Pattern taken from: http://fightingforalostcause.net/misc/2006/compare-email-regex.php (the very first one...)

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• How to lock Firefox tab to domain or URL pattern

  - by f3lix

  I know Firefox extensions that allow protecting (cannot be closed) and locking (cannot change URL) tabs. What I need is an extension that locks a tab to a certain domain or URL pattern. For example, I want to lock a tab to the domain example.com. As long as I follow links that are within this domain the tab should show normal (unlocked) behavior, but if I follow a link to another domain the link should be opened in new tab -- leaving the locked tab open with a URL within the locked domain. Even better would be the functionality to lock a tab to a URL pattern. If a URL matches the pattern it is opened in the current tab, otherwise it is opened in a new tab. Do you know something (preferably an extension for FF 8.0) that provides this kind of functionality.

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• Match exactly (and only) the pattern I specify in a grep command

  - by palswim

  Usually, grep searches for all lines containing a match for the pattern/parameter I specify. I would like to match just the pattern (i.e. not the whole line). So, if a file contains the lines: We said that we'll come. Unfortunately, we were delayed. Now, we're on our way. I want to find all contractions starting with "we" (regex pattern: we\'[a-z]+/i). And I'm looking for the output: we'll we're How do I do this (with grep or another Unix/Windows command-line tool)?

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• Applying the Decorator Pattern to Forms

  - by devoured elysium

  I am trying to apply the Decorator Design Pattern to the following situation: I have 3 different kind of forms: Green, Yellow, Red. Now, each of those forms can have different set of attributes. They can have a minimize box disabled, a maximized box disabled and they can be always on top. I tried to model this the following way: Form <---------------------------------------FormDecorator /\ /\ |---------|-----------| |----------------------|-----------------| GreenForm YellowForm RedForm MinimizeButtonDisabled MaximizedButtonDisabled AlwaysOnTop Here is my GreenForm code: public class GreenForm : Form { public GreenForm() { this.BackColor = Color.GreenYellow; } public override sealed Color BackColor { get { return base.BackColor; } set { base.BackColor = value; } } } FormDecorator: public abstract class FormDecorator : Form { private Form _decoratorForm; protected FormDecorator(Form decoratorForm) { this._decoratorForm = decoratorForm; } } and finally NoMaximizeDecorator: public class NoMaximizeDecorator : FormDecorator { public NoMaximizeDecorator(Form decoratorForm) : base(decoratorForm) { this.MaximizeBox = false; } } So here is the running code: static void Main() { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Application.Run(CreateForm()); } static Form CreateForm() { Form form = new GreenForm(); form = new NoMaximizeDecorator(form); form = new NoMinimizeDecorator(form); return form; } The problem is that I get a form that isn't green and that still allows me to maximize it. It is only taking in consideration the NoMinimizeDecorator form. I do comprehend why this happens but I'm having trouble understanding how to make this work with this Pattern. I know probably there are better ways of achieving what I want. I made this example as an attempt to apply the Decorator Pattern to something. Maybe this wasn't the best pattern I could have used(if one, at all) to this kind of scenario. Is there any other pattern more suitable than the Decorator to accomplish this? Am I doing something wrong when trying to implement the Decorator Pattern? Thanks

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