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  • Database theory - relationship between two tables

    - by iansinke
    I have a database with two tables - let's call them Foo and Bar. Each foo may be related to any number of bars, and each bar may be related to any number of foos. I want to be able to retrieve, with one query, the foos that are associated with a certain bar, and the bars that are associated with a certain foo. My question is, what is the best way of recording these relationships? Should I have a separate table with records of each relationship (e.g. two columns, foo and bar)? Should the foo table have a column for a list of bars, and vice versa? Is there another option that I'm overlooking? I'm using SQL Server, if that makes a difference.

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  • How do you draw like a Crayon?

    - by Simucal
    Crayon Physics Deluxe is a commercial game that came out recently. Watch the video on the main link to get an idea of what I'm talking about. It allows you to draw shapes and have them react with proper physics. The goal is to move a ball to a star across the screen using contraptions and shapes you build. While the game is basically a wrapper for the popular Box2D Physics Engine, it does have one feature that I'm curious about how it is implemented. Its drawing looks very much like a Crayon. You can see the texture of the crayon and as it draws it varies in thickness and darkness just like an actual crayon drawing would look like. The background texture is freely available here. Close up of crayon drawing - Note the varying darkness What kind of algorithm would be used to render those lines in a way that looks like a Crayon? Is it a simple texture applied with a random thickness and darkness or is there something more going on?

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  • MVVM Madness: Commands

    - by JP
    I like MVVM. I don't love it, but like it. Most of it makes sense. But, I keep reading articles that encourage you to write a lot of code so that you can write XAML and don't have to write any code in the code-behind. Let me give you an example. Recently I wanted to hookup a command in my ViewModel to a ListView MouseDoubleClickEvent. I wasn't quite sure how to do this. Fortunately, Google has answers for everything. I found the following articles: http://blog.functionalfun.net/2008/09/hooking-up-commands-to-events-in-wpf.html http://joyfulwpf.blogspot.com/2009/05/mvvm-invoking-command-on-attached-event.html http://sachabarber.net/?p=514 http://geekswithblogs.net/HouseOfBilz/archive/2009/08/27/adventures-in-mvvm-ndash-binding-commands-to-any-event.aspx http://marlongrech.wordpress.com/2008/12/13/attachedcommandbehavior-v2-aka-acb/ While the solutions were helpful in my understanding of commands, there were problems. Some of the aforementioned solutions rendered the WPF designer unusable because of a common hack of appending "Internal" after a dependency property; the WPF designer can't find it, but the CLR can. Some of the solutions didn't allow multiple commands to the same control. Some of the solutions didn't allow parameters. After experimenting for a few hours I just decided to do this: private void ListView_MouseDoubleClick(object sender, MouseButtonEventArgs e) { ListView lv = sender as ListView; MyViewModel vm = this.DataContext as MyViewModel; vm.DoSomethingCommand.Execute(lv.SelectedItem); } So, MVVM purists, please tell me what's wrong with this? I can still Unit test my command. This seems very practical, but seems to violate the guideline of "ZOMG... you have code in your code-behind!!!!" Please share your thoughts. Thanks in advance.

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  • UISplitView show different views in the detail pane

    - by Mark
    How can I change the view in the Details pane of the UISplitView so that its a completely different view? Im having a fair amount of trouble understanding how its all wired up and where things should go at the moment, could someone please enlighten me? What I would love to be able to do is to show a specific view based on what the user has selected in the UITableView on the left pane (this view could be an image, or a more complex view of a news article, etc... many different options) then when the user turns the iPad into portrait view, that view that was in the details pane changes to be its equivalent portrait view version. Does this make sense? How on earth would I do that? Just to brainstorm, here is what I was thinking: Create a Split View project Create 2 NIBs for each view: (with accompanying view controllers???) * PortraitNewsStory * LandscapeNewsStory * PortraitImageBrowser * LandscapeImageBrowser * etc... Create a UISplitView control using XCode Capture when a user rotates the iPad (should this be done in the RootViewController.m ?) Change the view of the DetailViewController how should I do this? profit??? Thanks Mark

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  • Conditional Markup in aspx

    - by Dynde
    Hi... I have a ListView. If I want to base the html markup on a condition in respects to the databound item, what would be the best way to do that? What I mean is, is there any other way then putting <% % if/else blocks directly in the markup? I'm aware that a really ugly way of doing it, is putting html markup in the database field, and just let the Eval() squeeze out the proper markup (I'm not doing that). I would like to avoid putting actual <% % C# blocks in the code as well. Any good ideas?

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  • MVP on Asp.Net WebForms

    - by Nicolas Irisarri
    I'm not clear about this.... When having a gridview on the View, is the controller who has to set up the Data source, columns, etc? or I just have to expose the DataBinding stuff, fire it from the controller and let the html/codebehind on the view handle all the rendering and wiring up? To be more precise: on the view should I have private GridView _gv public _IList<Poco> Source { get {_gv.DataSource;} set {_gv.DataSource = value; _gv.DataBind();} } Or should it be (from http://stackoverflow.com/questions/153222/mvp-pattern-passive-view-and-exposing-complex-types-through-iview-asp-net-web) private GridView _datasource; public DataSource { get { return _datasource; } set { _datasource = value; _datasource.DataBind(); } } Maybe I'm having it all wrong .... Where can I find an example that is not a "Hello world" example on MVP for ASP.Net???

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  • High-quality ERD generator for PostgresQL under Linux?

    - by Dave Jarvis
    Background MySQL Workbench can produce appealing and high-quality ERDs such as: Research I have not found a tool that even comes close for PostgreSQL. Tools I have found: dbVisualizer - Yellow squares. AquaFold - Yellow squares. SQL Developer - Coloured squares. Dia - Coloured squares. SchemaBank - Can't export to PNG; looks okay, nothing stellar. SchemaSpy - XML export makes it possible to write an XSL skin... Gliffy - Incompatible Flash version. Druid - No. pgAdmin3 - Not applicable? phpPgAdmin - Couldn't login without a 30-minute configuration battle. Requirements Looking for an ERD tool: Visually stunning by default Can reverse-engineer a PostgreSQL (or JDBC-compliant) database Runs on Linux (or under WINE) Export high-resolution PNG (or SVG) FOSS

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  • Thrift,.NET,Cassandra - Is this is right combination?

    - by Vadi
    I've been evaluating technology stack for developing a social network based application. Below are the stack I think could well suitable for this application type of application: GUI -- ASP.NET MVC, Flash (Flex) Business Services -- Thrift based services One of the advantage of using Thrift is to solve scaling problems that will come in future when the user base increases rapidly. All the business logic can be exposed as a services using REST,JSON etc., This also allows us to go with C++ or Erlang based services when situation demands. Database -- mySQL, CasSandara mySQL can be used for storing the data which needs to be persisted. Cassandara will be used for storing global identifiers to the persisted data. Since Cassandara is also very good at scaling by introducing more nodes this will leverage Thrift based services as well. And also there is native support between Cassandara and Thrift Cache Server -- Memcached Any requests from Business Services will only talk to Memcached if any non-dirty data is required, otherwise there will be some background jobs that will invalidate the cache from database. The question is: Is the Thrift which is open-sourced one is production-ready? Is it the right stack for services layer to choose when the application (GUI) is primarily gets developed in ASP.NET and DB is mysql? Is there any other caveats that anyone here experienced? One of the main objective behind this stack is to easily scale up with more nodes and also this helps us to use Linux boxes, it will reduce our cost significantly Thoughts please ..

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  • C# Create Snap To Grid Functionality

    - by Nathan
    I am trying to create some snap to grid functionality to be used at run time but I am having problems with the snapping part. I have successfully drawn a dotted grid on a panel but when I add a label control to the panel how to I snap the top, left corner of the label to the nearest dot? Thanks

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  • Patterns for implementing field change tracking.

    - by David
    Hi all For one of my recent projects, I had to implement field change tracking. So anytime the user changed a value of a field, the change was recorded in order to allow full auditing of changes. In the database, I implemented this as a single table 'FieldChanges' with the following fields: TableName, FieldName, RecordId, DateOfChange, ChangedBy, IntValue, TextValue, DateTimeValue, BoolValue. The sproc saving changes to an object determines for each field whether it has been changed and inserts a record into FieldChanges if it has: if the type of the changed field is int, it records it in the IntValue field in the FieldChanges table, etc. This means that for any field in any table with any id value, I can query the FieldChanges table to get a list of changes. This works quite well but is a bit clumsy. Can anyone else who has implemented similar functionality suggest a better approach, and why they think it's better? I'd be really interested - thanks. David

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  • Working out global tab order algorithmically?

    - by Mrgreen
    We have a proprietry system where we can configure fields on indiviual forms. However these fields have a global tab order (we cannot specify for a specific form). We have a bunch of forms (35 in total) which share a lot of different fields. Each form has a specific tab/edit order that needs to be configured. Example: Form 1 has fields A,B,C,D in that order. Form 2 has fields E,F,G,A in that order. Form 3 has fields E,B,H,I in that order. The global tab orders would be E,F,G,A,B,C,D,H,I Notice how A needs to come before B yet after G. Is there any easy way to work this out using the tab order lists for each form? I need to merge this tab order information into a single global tab order list. I have over 200 fields in total and it is near impossible to do by hand.

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  • singleton vs factory?

    - by fayer
    i've got 3 Log classes that all implements iLog interface: DatabaseLog FileLog ScreenLog there can only be one instance of them. initially i though of using single pattern for each class but then i thought why not use a factory for instantiation instead, cause then i wont have to create single pattern for each one of them and for all future Log classes. and maybe someone would want them as multiple objects in the future. so my questions is: should i use factory or singleton pattern here?

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  • Repository pattern with lazying loading using POCO

    - by Simon G
    Hi, I'm in the process of starting a new project and creating the business objects and data access etc. I'm just using plain old clr objects rather than any orms. I've created two class libraries: 1) Business Objects - holds all my business objects, all this objects are light weight with only properties and business rules. 2) Repository - this is for all my data access. The majority of my objects will have child list in and my question is what is the best way to lazy load these values as I don't want to bring back unnecessary information if I dont need to. I've thought about when using the "get" on the child property to check if its "null" and if it is call my repository to get the child information. This has two problems from what I can see: 1) The object "knows" how to get itself I would rather no data access logic be held in the object. 2) This required both classes to reference each other which in visual studio throws a circular dependency error. Does anyone have any suggestions on how to overcome this issue or any recommendations on my projects layout and where it can be improved? Thanks

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  • Why is IoC / DI not common in Python?

    - by tux21b
    In Java IoC / DI is a very common practice which is extensively used in web applications, nearly all available frameworks and Java EE. On the other hand, there are also lots of big Python web applications, but beside of Zope (which I've heard should be really horrible to code) IoC doesn't seem to be very common in the Python world. (Please name some examples if you think that I'm wrong). There are of course several clones of popular Java IoC frameworks available for Python, springpython for example. But none of them seems to get used practically. At least, I've never stumpled upon a Django or sqlalchemy+<insert your favorite wsgi toolkit here> based web application which uses something like that. In my opinion IoC has reasonable advantages and would make it easy to replace the django-default-user-model for example, but extensive usage of interface classes and IoC in Python looks a bit odd and not »pythonic«. But maybe someone has a better explanation, why IoC isn't widely used in Python.

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  • Are soft deletes a good idea?

    - by Khou
    Are soft deletes a good idea or a bad idea? Instead of actually deleting a record in your database, you would just flag it as "IsDeleted" = true, and upon recovery of the record you could just flag it as "False". Is this a good idea?

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  • Which pattern should be used for editing properties with modal view controller on iPhone?

    - by Matthew Daugherty
    I am looking for a good pattern for performing basic property editing via a modal view on the iPhone. Assume I am putting together an application that works like the Contacts application. The "detail" view controller displays all of the contact's properties in a UITableView. When the UITableView goes into edit mode a disclosure icon is displayed in the cells. Clicking a cell causes a modal "editor" view controller to display a view that allows the user to modify the selected property. This view will often contain only a single text box or picker. The user clicks Cancel/Save and the "editor" view is dismissed and the "detail" view is updated. In this scenario, which view is responsible for updating the model? The "editor" view could update the property directly using Key-Value Coding. This appears in the CoreDataBooks example. This makes sense to me on some level because it treats the property as the model for the editor view controller. However, this is not the pattern suggested by the View Controller Programming Guide. It suggests that the "editor" view controller should define a protocol that the "detail" controller adopts. When the user indicates they are done with the edit, the "detail" view controller is called back with the entered value and it dismisses the "editor" view. Using this approach the "detail" controller updates the model. This approach seems problematic if you are using the same "editor" view for multiple properties since there is only a single call-back method. Would love to get some feedback on what approach works best.

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  • Entity Attribute Value Database vs. strict Relational Model Ecommerce question

    - by Dr. Zim
    It is safe to say that the EAV/CR database model is bad. That said, Question: What database model, technique, or pattern should be used to deal with "classes" of attributes describing e-commerce products which can be changed at run time? In a good E-commerce database, you will store classes of options (like TV resolution then have a resolution for each TV, but the next product may not be a TV and not have "TV resolution"). How do you store them, search efficiently, and allow your users to setup product types with variable fields describing their products? If the search engine finds that customers typically search for TVs based on console depth, you could add console depth to your fields, then add a single depth for each tv product type at run time. There is a nice common feature among good e-commerce apps where they show a set of products, then have "drill down" side menus where you can see "TV Resolution" as a header, and the top five most common TV Resolutions for the found set. You click one and it only shows TVs of that resolution, allowing you to further drill down by selecting other categories on the side menu. These options would be the dynamic product attributes added at run time. Further discussion: So long story short, are there any links out on the Internet or model descriptions that could "academically" fix the following setup? I thank Noel Kennedy for suggesting a category table, but the need may be greater than that. I describe it a different way below, trying to highlight the significance. I may need a viewpoint correction to solve the problem, or I may need to go deeper in to the EAV/CR. Love the positive response to the EAV/CR model. My fellow developers all say what Jeffrey Kemp touched on below: "new entities must be modeled and designed by a professional" (taken out of context, read his response below). The problem is: entities add and remove attributes weekly (search keywords dictate future attributes) new entities arrive weekly (products are assembled from parts) old entities go away weekly (archived, less popular, seasonal) The customer wants to add attributes to the products for two reasons: department / keyword search / comparison chart between like products consumer product configuration before checkout The attributes must have significance, not just a keyword search. If they want to compare all cakes that have a "whipped cream frosting", they can click cakes, click birthday theme, click whipped cream frosting, then check all cakes that are interesting knowing they all have whipped cream frosting. This is not specific to cakes, just an example.

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  • Fastest gap sequence for shell sort ?

    - by Tony
    According to Marcin Ciura's Optimal (best known) sequence of increments for shell sort algorithm. The best sequence for shellsort is 1, 4, 10, 23, 57, 132, 301, 701... But how can I generate such a sequence ? In Marcin Ciura's paper he said : Both Knuth’s and Hibbard’s sequences are relatively bad, because they are defined by simple linear recurrences but most algorithm books I searched , they all tend to use Knuth’s sequence : k = 3k + 1 ; because it's easy to generate , what's your way of generating shellsort sequence ?

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  • Using MongoDB with Ruby On Rails and the Mongomapper plugin

    - by Micke
    Hello, i am currently trying to learn Ruby On Rails as i am a long-time PHP developer so i am building my own community like page. I have came pritty far and have made the user models and suchs using MySQL. But then i heard of MongoDB and looked in to it a little bit more and i find it kinda nice. So i have set it up and i am using mongomapper for the connection between rails and MongoDB. And i am now using it for the News page on the site. I also have a profile page for every User which includes their own guestbook so other users can come to their profile and write a little message to them. My thought now is to change the User models from using MySQL to start using MongoDB. I can start by showing how the models for each User is set up. The user model: class User < ActiveRecord::Base has_one :guestbook, :class_name => "User::Guestbook" The Guestbook model model: class User::Guestbook < ActiveRecord::Base belongs_to :user has_many :posts, :class_name => "User::Guestbook::Posts", :foreign_key => "user_id" And then the Guestbook posts model: class User::Guestbook::Posts < ActiveRecord::Base belongs_to :guestbook, :class_name => "User::Guestbook" I have divided it like this for my own convenience but now when i am going to try to migrate to MongoDB i dont know how to make the tables. I would like to have one table for each user and in that table a "column" for all the guestbook entries since MongoDB can have a EmbeddedDocument. I would like to do this so i just have one Table for each user and not like now when i have three tables just to be able to have a guestbook. So my thought is to have it like this: The user model: class User include MongoMapper::Document one :guestbook, :class_name => "User::Guestbook" The Guestbook model model: class User::Guestbook include MongoMapper::EmbeddedDocument belongs_to :user many :posts, :class_name => "User::Guestbook::Posts", :foreign_key => "user_id" And then the Guestbook posts model: class User::Guestbook::Posts include MongoMapper::EmbeddedDocument belongs_to :guestbook, :class_name => "User::Guestbook" But then i can think of one problem.. That when i just want to fetch the user information like a nickname and a birthdate then it will have to fetch all the users guestbook posts. And if each user has like a thousand posts in the guestbook it will get really much to fetch for the system. Or am i wrong? Do you think i should do it any other way? Thanks in advance and sorry if i am hard to understand but i am not so educated in the english language :)

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  • Recommend .NET data access layer/middle tier

    - by Simon G
    Hi, I'm currently creating an MVC application that will likely to expand to include a silverlight, wpf and possible windows phone all using the same data. So I've created a class library to keep all my objects in and I've created the MVC app. My question is what would be the best way to access the data? Taking into account possible expansion in the future. Should I use web services/WCF? RIA Services? Remoting? Or something else. What have people used in the past and what do you recommend? Thanks

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  • Help:Graph contest problem: maybe a modified Dijkstra or another alternative algorithm

    - by newba
    Hi you all, I'm trying to do this contest exercise about graphs: XPTO is an intrepid adventurer (a little too temerarious for his own good) who boasts about exploring every corner of the universe, no matter how inhospitable. In fact, he doesn't visit the planets where people can easily live in, he prefers those where only a madman would go with a very good reason (several millions of credits for instance). His latest exploit is trying to survive in Proxima III. The problem is that Proxima III suffers from storms of highly corrosive acids that destroy everything, including spacesuits that were especially designed to withstand corrosion. Our intrepid explorer was caught in a rectangular area in the middle of one of these storms. Fortunately, he has an instrument that is capable of measuring the exact concentration of acid on each sector and how much damage it does to his spacesuit. Now, he only needs to find out if he can escape the storm. Problem The problem consists of finding an escape route that will allow XPTOto escape the noxious storm. You are given the initial energy of the spacesuit, the size of the rectangular area and the damage that the spacesuit will suffer while standing in each sector. Your task is to find the exit sector, the number of steps necessary to reach it and the amount of energy his suit will have when he leaves the rectangular area. The escape route chosen should be the safest one (i.e., the one where his spacesuit will be the least damaged). Notice that Rodericus will perish if the energy of his suit reaches zero. In case there are more than one possible solutions, choose the one that uses the least number of steps. If there are at least two sectors with the same number of steps (X1, Y1) and (X2, Y2) then choose the first if X1 < X2 or if X1 = X2 and Y1 < Y2. Constraints 0 < E = 30000 the suit's starting energy 0 = W = 500 the rectangle's width 0 = H = 500 rectangle's height 0 < X < W the starting X position 0 < Y < H the starting Y position 0 = D = 10000 the damage sustained in each sector Input The first number given is the number of test cases. Each case will consist of a line with the integers E, X and Y. The following line will have the integers W and H. The following lines will hold the matrix containing the damage D the spacesuit will suffer whilst in the corresponding sector. Notice that, as is often the case for computer geeks, (1,1) corresponds to the upper left corner. Output If there is a solution, the output will be the remaining energy, the exit sector's X and Y coordinates and the number of steps of the route that will lead Rodericus to safety. In case there is no solution, the phrase Goodbye cruel world! will be written. Sample Input 3 40 3 3 7 8 12 11 12 11 3 12 12 12 11 11 12 2 1 13 11 11 12 2 13 2 14 10 11 13 3 2 1 12 10 11 13 13 11 12 13 12 12 11 13 11 13 12 13 12 12 11 11 11 11 13 13 10 10 13 11 12 8 3 4 7 6 4 3 3 2 2 3 2 2 5 2 2 2 3 3 2 1 2 2 3 2 2 4 3 3 2 2 4 1 3 1 4 3 2 3 1 2 2 3 3 0 3 4 10 3 4 7 6 3 3 1 2 2 1 0 2 2 2 4 2 2 5 2 2 1 3 0 2 2 2 2 1 3 3 4 2 3 4 4 3 1 1 3 1 2 2 4 2 2 1 Sample Output 12 5 1 8 Goodbye cruel world! 5 1 4 2 Basically, I think we have to do a modified Dijkstra, in which the distance between nodes is the suit's energy (and we have to subtract it instead of suming up like is normal with distances) and the steps are the ....steps made along the path. The pos with the bester binomial (Energy,num_Steps) is our "way out". Important : XPTO obviously can't move in diagonals, so we have to cut out this cases. I have many ideas, but I have such a problem implementing them... Could someone please help me thinking about this with some code or, at least, ideas? Am I totally wrong?

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