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• SQL Server concurrency and generated sequence

  - by Goyuix

  I need a sequence of numbers for an application, and I am hoping to leverage the abilities of SQL Server to do it. I have created the following table and procedure (in SQL Server 2005): CREATE TABLE sequences ( seq_name varchar(50) NOT NULL, seq_value int NOT NULL ) CREATE PROCEDURE nextval @seq_name varchar(50) AS BEGIN DECLARE @seq_value INT SET @seq_value = -1 UPDATE sequences SET @seq_value = seq_value = seq_value + 1 WHERE seq_name = @seq_name RETURN @seq_value END I am a little concerned that without locking the table/row another request could happen concurrently and end up returning the same number to another thread or client. This would be very bad obviously. Is this design safe in this regard? Is there something I can add that would add the necessary locking to make it safe? Note: I am aware of IDENTITY inserts in SQL Server - and that is not what I am looking for this in particular case. Specifically, I don't want to be inserting/deleting rows. This is basically to have a central table that manages the sequential number generator for a bunch of sequences.

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• Javascript object encapsulation that tracks changes

  - by Raynos

  Is it possible to create an object container where changes can be tracked Said object is a complex nested object of data. (compliant with JSON). The wrapper allows you to get the object, and save changes, without specifically stating what the changes are Does there exist a design pattern for this kind of encapsulation Deep cloning is not an option since I'm trying to write a wrapper like this to avoid doing just that. The solution of serialization should only be considered if there are no other solutions. An example of use would be var foo = state.get(); // change state state.update(); // or state.save(); client.tell(state.recentChange()); A jsfiddle snippet might help : http://jsfiddle.net/Raynos/kzKEp/ It seems like implementing an internal hash to keep track of changes is the best option. [Edit] To clarify this is actaully done on node.js on the server. The only thing that changes is that the solution can be specific to the V8 implementation.

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• Return an opaque object to the caller without violating type-safety

  - by JS Bangs

  I have a method which should return a snapshot of the current state, and another method which restores that state. public class MachineModel { public Snapshot CurrentSnapshot { get; } public void RestoreSnapshot (Snapshot saved) { /* etc */ }; } The state Snapshot class should be completely opaque to the caller--no visible methods or properties--but its properties have to be visible within the MachineModel class. I could obviously do this by downcasting, i.e. have CurrentSnapshot return an object, and have RestoreSnapshot accept an object argument which it casts back to a Snapshot. But forced casting like that makes me feel dirty. What's the best alternate design that allows me to be both type-safe and opaque?

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• How to relate keywords to records - Many to Many

  - by webworm

  Hi All, I am looking for suggestions on database design for a sample jobs listing application. I have many jobs that I would like to associate various keywords with. Each job can have multiple keywords. I would like to store the keywords in a seperate table instead of in a field within the Job table so as to avoid mispellings in keywords. What is the best way to relate keywords to the jobs? I was thinking of using an intermediary table that would have a many to many relationship linking keywords to jobs. Is this the best way to go or should I just have a field in the Job table that contains multiple keywords? Thanks for any suggestions.

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• Rails: Serializing objects in a database?

  - by keruilin

  I'm looking for some general guidance on serializing objects in a database. What are serialized objects? What are some best-practice scenarios for serializing objects in a DB? What attributes do you use when creating the column in the DB so you can use a serialized object? How to save a serialized object? And how to access the serialized object and its attributes? (Using hashes?)

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• How do I manipulate a tree of immutable objects?

  - by Frederik

  I'm building an entire application out of immutable objects so that multi-threading and undo become easier to implement. I'm using the Google Collections Library which provides immutable versions of Map, List, and Set. My application model looks like a tree: Scene is a top-level object that contains a reference to a root Node. Each Node can contain child Nodes and Ports. An object graph might look like this: Scene | +-- Node | +-- Node | +- Port +-- Node | +- Port +- Port If all of these objects are immutable, controlled by a top-level SceneController object: What is the best way to construct this hierarchy? How would I replace an object that is arbitrarily deep in the object tree? Is there a way to support back-links, e.g. a Node having a "parent" attribute?

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• How can I get a property as an Entity in Action of Asp.Net Mvc ?

  - by Felipe

  Hi all, i'd like to know how can I get a property like an entity, for example: My Model: public class Product { public int Id { get; set; } public string Name { get; set; } public Category Category { get; set; } } View: Name: <%=Html.TextBoxFor(x => x.Name) %> Category: <%= Html.DropDownList("Category", IEnumerable<SelectListItem>)ViewData["Categories"]) %> Controller: public ActionResult Save(Product product) { /// produtct.Category ??? } and how is the category property ? It's fill by the view ? ASP.Net MVC know how to fill this object by ID ? Thanks!

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• mvc - how to avoid log out when refresh a page

  - by user235973457

  I have built the MVC application with WCF service. The major problem I have experienced with refreshing page. I have created a login page with session (username and password). But when you refresh the home page by pressing F5, it would automatically log out. That is my problem. I need to stay the home page after refresh. I have been googling around to find a solution but it seems not helpful. Any idea? Your advise or code example much appreciated.

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• benefit of having a factory for object creation?

  - by ajsie

  I'm trying to understand the factory design pattern. I don't understand why it's good to have a middleman between the client and the product (object that the client wants). example with no factory: $mac = new Mac(); example with a factory: $appleStore = new AppleStore(); $mac = $appleStore->getProduct('mac'); How does the factory pattern decouple the client from the product? Could someone give an example of a future code change that will impact on example 1 negative, but positive in example 2 so I understand the importance of decoupling? Thanks.

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• How to do comments in Activity Stream? (like Facebook)

  - by fesja

  Hi, I'm starting to develop an activity stream. I've read both How to implement the activity stream in a social network and What’s the best manner of implementing a social activity stream?. What I haven't found is the best way to add comments to the activities. As in facebook, each comment can be commented by another person. If each activity comment is saved as another activity, then I would not be able to get the activity of that comment without doing a query. So the solution I'm thinking is to save the comments inside the serialize data field of each activity. If the user wants to delete his comment, I would have to update that activity. Is this the correct solution? Is there a better approach? Thanks!

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• Drupal and Back-End Complexity

  - by Brian

  Currently I am working on a school website, and we are still in the decision-making process of choosing a framework (we know that we're not using Joomla! or hand-coding). Drupal came up as a viable choice, and currently, that is my best bet for the site. However, I have an issue with CMS's in general. I would like to develop a quite complicated and specifically custom-suited back-end application for teachers to interact with individual students, including the design of shared/custom calendars, announcement privileges, etc. I currently have a bit of expertise with HTML, CSS, PHP, MySQL, and I could wrap my head around some JavaScript and AJAX stuff if need-be. However, would such a complicated application work with Drupal (in that I could create it to specifically suite my purposes)?

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• How to handle request/response propagation up and down a widget hierarchy in a GUI app?

  - by fig-gnuton

  Given a GUI application where widgets can be composed of other widgets: If the user triggers an event resulting in a lower level widget needing data from a model, what's the cleanest way to be able to send that request to a controller (or the datastore itself)? And subsequently get the response back to that widget? Presumably one wouldn't want the controller or datastore to be a singleton directly available to all levels of widgets, or is this an acceptable use of singleton? Or should a top level controller be injected as a dependency through a widget hierarchy, as far down as the lowest level widget that might need that controller? Or a different approach entirely?

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• This is right way for database?

  - by ciss

  Hello, i have some issue with database. Okay, i have two models - Page and Item. Page for displaying some content. Item - this is item discription. So, i work on small ecommerce shop. Okay, all of this models can have some comments. So, this is my Comments model at this moment: Comments - string : id text : body integer : page_id integer : item_id So when some one add comment to page - page_id will be filled with current Page id. And if some one add comment to item - item_id will be filled. Okay, i know what the best way is to create STI or Polymorphic assoc, but does i really need this way for my situation? Sorry for my bad english, i'm from Russia.=)

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• BlackBerry - Multiple Screens or Single Screen with Content Manager?

  - by Max Gontar

  Hi! I've seen projects which use many screens each one for different layout and functionality. I've seen projects with only one screen (like wizard workflow) where content is changed on user interaction (and this seems to be logical to use single screen in wizards). But also I've seen projects (apps like game or messenger or phone settings utility) which use single screen for different functionalities. I can see such advantages of having single screen in app: keep same decoration design and menu or toolbar (which may be also achieved with inheritance) keep single screen in ui stack (which may be achieved by pop/push screen) easy to handle data over application Can you tell other advantages/disadvantages of single screen app? When its better to use this approach? Thank you!

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• c++ - what is faster ?

  - by VaioIsBorn

  If we have the following 2 snippets of code in c++ that do the same task: int a, b=somenumber; while(b > 0) { a = b % 3; b /= 3; } or int b=somenumber; while(b > 0) { int a=b%3; b /= 3; } I don't know much about computer architecture/c++ design, but i think that the first code is faster because it declares the integer a at the beginning and just uses it in the while-loop, and in the second code the integer a is being declared everytime the while-loop starts over. Can some one help me with this, am i correct or what and why ?

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• Refactoring FAT client legacy application

  - by Paul

  I am working on a fat client legacy C++ application which has a lot of business logic mixed in with the presentation side of things. I want to clean things out and refactor the code out completely, so there is a clear seperation of concerns. I am looking at MVC or some other suitable design pattern in order to achieve this. I would like to get recommendations from people who have walked this road before - Do I use MVP or MVC (or another pattern)? What is/are the best practices for undertaking something like this (i.e. useful steps/checks) ?

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• C++ Inheritance Question

  - by shaz

  I have a base class MessageHandler and 2 derived classes, MessageHandler_CB and MessageHandler_DQ. The derived classes redefine the handleMessage(...) method. MH_DQ processes a message and puts the result in a deque while MH_CB processes the message and then executes a callback function. The base class has a static callback function that I pass along with a this pointer to a library which calls the static callback when a new message is available for processing. My problem comes when I am in the static callback with a void * pointing to either a MH_DQ or a MH_CB. If I cast it to the base class the empty MessageHandler::handleMessage(...) method is called, rather than the version in the appropriate derived class. What is the best way to address this situation from a design perspective and/or what language features might help me to implement a solution to my problem? Thanks in advance!

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• Order records from multiple models by attribute

  - by Labuschin

  Given the three models “message”, “profile” and “comment” i want to merge them into one list, ordered by their common attribute “created_at”. I want to accomplish something like the project overview in Basecamp - see 3) here: http://basecamphq.com/tour#overview

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• Need help on understanding Mobile First concept

  - by RhymeGuy

  So, I worked on responsive sites before but I'm on my way to build my first responsive site now. I opened some articles on the subject, and boom: Mobile First.. I have no idea how I skipped that concept till now. From the beginning I cant seem to understand whole thing (except that number of mobile devices will take out soon desktop computers) and here is why. How I'm supposed to know how my site will look for desktop version, if I design it for mobile first? I mean, on the smallest device I will have to eventually hide some content etc, how I'm supposed to know what to hide and move things, when I don't know how the site will look on bigger screen? Isn't stripping the things easier?!?! For me (right now), the Mobile First concept looks to me like building pyramid upside down.

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• Very basic database theory.

  - by John R

  I have a set of tables to show the relationship between organziations and supporters below. Although I have done some basic mySQL querries, I know very little about database 'design'. I plan to querry the database for: -a list of contributors to a specific organization... or, -a list of organizations that a specific suporter supports. The database tables for organiations and contributors may have other columns in the future and recieve a lesser amount of querries based on that information. A | X A | Y A | Z B | X B | Y C | X C | Z How should the tables be set up? I assume that there should be a third table, but there is still redundent information in the third table. Is there a better way of setting up the tables? +----+-------+ +-------------+----------+ +----+-------+ | id | org | | org | contr | | id | contr.| +----+-------+ +-------------+----------+ +----+-------+ | 1 | A | | 1 | 1 | | 1 | X | | 2 | B | | 1 | 2 | | 2 | Y | | 3 | C | | 1 | 3 | | 3 | Z | +----+-------+ | 2 | 1 | +----+-------+ | 2 | 2 | | 3 | 1 | | 3 | 3 | +-------------+----------+

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• Elegant ways of displaying a GridView with lots of columns (ASP.NET)

  - by Chris

  Hi, just a general design question that I'd like to hear some of your opinions on. I am designing a system for a client, and I'm using GridView' a lot. They need a lot of columns to be displayed in some of these, and I've had to resort to using a panel with a horizontal scrollbar. This presents some issues - keeping track of which row is which is difficult, even with alternating row colours, and it's generally pretty ugly. How have you dealt with these issues before? Are there any sort of AJAX controls that could help, so some data could be only displayed on hover or such? Or any other general ideas.

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• CakePHP ACL use case(s)

  - by Jonathan

  I have got a simple web app in development, i want to establish a couple of user groups; Admin, Doctors & Patients. Each group would have their access restricted to particular controller actions rather than individual content. So for example, Doctors can view patient records (index & view actions), but cannot delete them. Usually i would create a groups model, and assign the various users to a group. And filter in the beforeFilter() method to determine if the user has access. But if ACL can do the job, why right the code, right? Thanks

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• How to resolve IPs in DNS based on the subnet of the requesting client?

  - by Nohsib

  Is it possible to configure Bind9 or other DNS to resolve the domain name of a machine into different IPs based on the subnet of the requesting client? e.g. Say the same service is running on 2 different application servers at different geographical points and based on the incoming request to resolve the domain name, the name server provides the IP of the application server based on the requesting client's IP, so the service could be offered by servers that are geographically closer to the client. In short, something like a CDN but just the IP resolution part based on the client's subnet. Is this configurable in any DNS?

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• How do I configure VMware View location-based printing to use Active Directory Groups?

  - by Jason Pearce

  I am attempting to configure VMware View 4.5's Location-Based Printing, which leverages an included OEM version of ThinPrint, to assign printers to active directory groups. The location-based printing feature maps printers that are physically near client systems to VMware View desktops. I am using the Active Directory group policy setting AutoConnect Location-based Printing for VMware View, which is located in the Microsoft Group Policy Object Editor in the Software Settings folder under Computer Configuration. The AutoConnect Location-based Printing for VMware View appearst to be just a name translation table. It permits me to assign a specific printer or printers to an IP Range, Client Name, Mac Address, User, or User Group. I'm attempting to assign printers to active directory user groups. I have created a new active directory group for each printer that I intend to use in VMware View desktop pools. I will then assign active directory users to the active directory groups that represent each network printer. Example: doej is a member of the PTR-FLOOR2-NORTH-ROOM255 active directory group. Using AutoConnect, I assigned the group to receive a network printer by adding PTR-FLOOR2-NORTH-ROOM255 in the User/Group column. Problem: When doej logs in to his VDI session, the printer is not present. However, if I use a wildcard "*" in the User/Group column instead of the specific PTR-FLOOR2-NORTH-ROOM255 active directory group, the printer is present and functions as designed. Alternatives: I have tried assigning printers to active directory groups within AutoConnect in the following ways, all unsuccesfull: PTR-FLOOR2-NORTH-ROOM255 domainexample\PTR-FLOOR2-NORTH-ROOM255 domainexample.local\PTR-FLOOR2-NORTH-ROOM255 Confirmation: The information used to map the printer to the VMware View desktop is stored in a registry entry on the View desktop in HKEY_LOCAL_MACHINE\SOFTWARE\Policies\thinprint\tpautoconnect. For each of these examples, I have reviewed the registry entry and can confirm that the desktop is receiving the information from the AutoConnect translation table. Summary: Can anyone provide an example of how to configure VMware View 4.5's Location-Based Printing so that I may assign network printers to active directory groups via the included AutoConnect tool? I would welcome a clear example of a working configuration. Thank you.

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• How to balance a non-symmetric "extension" based game?

  - by Klaim

  Most strategy games have fixed units and possible behaviours. However, think of a game like Magic The Gathering : each card is a set of rules. Regularly, new sets of card types are created. I remember that the firsts editions of the game have been said to be prohibited in official tournaments because the cards were often too powerful. Later extensions of the game provided more subtle effects/rules in cards and they managed to balance the game apparently effectively, even if there is thousands of different cards possible. I'm working on a strategy game that is a bit in the same position : every units are provided by extensions and the game is thought to be extended for some years, at least. The effects variety of the units are very large even with some basic design limitations set to be sure it's manageable. Each player choose a set of units to play with (defining their global strategy) before playing (like chooseing a themed deck of Magic cards). As it's a strategy game (you can think of Magic as a strategy game too in some POV), it's essentially skirmish based so the game have to be fair, even if the players don't choose the same units before starting to play. So, how do you proceed to balance this type of non-symmetric (strategy) game when you know it will always be extended? For the moment, I'm trying to apply those rules but I'm not sure it's right because I don't have enough design experience to know : each unit would provide one unique effect; each unit should have an opposite unit that have an opposite effect that would cancel each others; some limitations based on the gameplay; try to get a lot of beta tests before each extension release? Looks like I'm in the most complex case?

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