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  • How to determine which inheriting class is using an abstract class' methods.

    - by Kin
    In my console application have an abstract Factory class "Listener" which contains code for listening and accepting connections, and spawning client classes. This class is inherited by two more classes (WorldListener, and MasterListener) that contain more protocol specific overrides and functions. I also have a helper class (ConsoleWrapper) which encapsulates and extends System.Console, containing methods for writing to console info on what is happening to instances of the WorldListener and MasterListener. I need a way to determine in the abstract ListenerClass which Inheriting class is calling its methods. Any help with this problem would be greatly appreciated! I am stumped :X Simplified example of what I am trying to do. abstract class Listener { public void DoSomething() { if(inheriting class == WorldListener) ConsoleWrapper.WorldWrite("Did something!"); if(inheriting class == MasterListener) ConsoleWrapper.MasterWrite("Did something!"); } } public static ConsoleWrapper { public void WorldWrite(string input) { System.Console.WriteLine("[World] {0}", input); } } public class WorldListener : Listener { public void DoSomethingSpecific() { ConsoleWrapper.WorldWrite("I did something specific!"); } } public void Main() { new WorldListener(); new MasterListener(); } Expected output [World] Did something! [World] I did something specific! [Master] Did something! [World] I did something specific!

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  • Is this a situation where Qt Model/View architecture is not useful?

    - by csmithmaui
    Hi, I am writing a GUI based application where I read a string of values from serial port every few seconds and I need to display most of the values in some type graphical indicator(I was thinking of QprogressBar maybe) that displays the range and the value. Some of the other data that I am parsing from the string are the date and fault codes. Also, the data is hierarchical. I wanted to use the model/view architecture of Qt because I have been interested in MVC stuff for a while but have never quite wrapped my brain around how to implement it very well. As of now, I have subclassed QAbstractItemModel and in the model I read the serial port and wrap the items parsed from the string in a Tree data structure. I can view all of the data in a QtreeView with no issues. I have also began to subclass QAbstractItemView to build my custom view with all of the Graphical Indicators and such. This is where I am getting stuck. It seems to me that in order for me to design a view that knows how to display my custom model the view needs to know exactly how all of the data in the model is organized. Doesn't that defeat the purpose of Model/View? The QTreeView I tested the model with is basically just displaying the model as it is setup in the Tree structure but I don't want to do that because the data is not all of the same type. Is the type of data or the way you would like to present it to the user a determining factor in whether or not you should use this architecture? I always assumed it was just always better to design in an MVC style. It seems to me like it might have been better to just subclass QWidget and then read in from the serial port and update all of subwidgets(graphical indicators, labels, etc...) from the subclass. Essentially, do everything in one class. Does anybody understand this issue that can explain to me either what I am missing or why I shouldn't be doing it this way. As of now I am a little confused. Thanks so much for any help!

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  • Scripting Languages vs. Compiled Languages for web development

    - by Austin Hyde
    Though I come from a purely PHP background on the web development side of programming, I have also spent much time with C# and C++ on the desktop. I don't really want to spark any flame wars, but: When should you use scripting languages over compiled languages for website development? (and vice versa) Just to clarify, for the sake of this question, I define a "scripting language" to mean an interpreted language like PHP, Python, or Ruby, and a "compiled language" to mean a strongly typed, compiled language like C#, C++, Java, or VB.

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  • Should I have different models and views for no user data than for some user data?

    - by Sam Holder
    I'm just starting to learn asp.net mvc and I'm not sure what the right thing to do is. I have a user and a user has a collection of (0 or more) reminders. I have a controller for the user which gets the reminders for the currently logged in user from a reminder service. It populates a model which holds some information about the user and the collection of reminders. My question is should I have 2 different views, one for when there are no reminders and one for when there are some reminders? Or should I have 1 view which checks the number of reminders and displays different things? Having one view seems wrong as then I end up with code in my view which says if (Model.Reminders.Count==0){//do something} else {do something else}, and having logic in the view feels wrong. But if I want to have 2 different views then I'd like to have some code like this in my controller: [Authorize] public ActionResult Index() { MembershipUser currentUser = m_membershipService.GetUser(); IList<Reminder> reminders = m_reminderRepository.GetReminders(currentUser); if (reminders.Count == 0) { var model = new EmptyReminderModel { Email = currentUser.Email, UserName = currentUser.UserName }; return View(model); } else { var model = new ReminderModel { Email = currentUser.Email, UserName = currentUser.UserName, Reminders = reminders }; return View(model); } but obviously this doesn't compile as the View can't take both different types. So if I'm going to do this should I return a specific named view from my controller, depending on the emptiness of the reminders, or should my Index() method redirect to other actions like so: [Authorize] public ActionResult Index() { MembershipUser currentUser = m_membershipService.GetUser(); IList<Reminder> reminders = m_reminderRepository.GetReminders(currentUser); if (reminders.Count == 0) { return RedirectToAction("ShowEmptyReminders"); } else { return RedirectToAction("ShowReminders"); } } which seems nicer but then I need to re-query the reminders for the current user in the ShowReminders action. Or should I be doing something else entirely?

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  • Is it good or bad practice to use var everywhere? [closed]

    - by Earlz
    Possible Duplicate: Use of var keyword in C# Hello, I've recently been discovering the awesomeness that is the var keyword in C#. Well, I didn't think about it before but I just wrote lines of code that are along the lines of var con=CreateNewConnection(); Where this would usually be IdbConnection con=CreateNewConnection(); Is this a good use of var? Is it possible to use var too often? Are there any downsides to using it? Also, one more point of consideration: We are not worried about backwards compatability. We just care that it runs on .NET 3.5

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  • How to refactor use of the general Exception?

    - by Colin
    Our code catches the general exception everywhere. Usually it writes the error to a log table in the database and shows a MessageBox to the user to say that the operation requested failed. If there is database interaction, the transaction is rolled back. I have introduced a business logic layer and a data access layer to unravel some of the logic. In the data access layer, I have chosen not to catch anything and I also throw ArgumentNullExceptions and ArgumentOutOfRangeExceptions so that the message passed up the stack does not come straight from the database. In the business logic layer I put a try catch. In the catch I rollback the transaction, do the logging and rethrow. In the presentation layer there is another try catch that displays a MessageBox. I am now thinking about catching a DataException and an ArgumentException instead of an Exception where I know the code only accesses a database. Where the code accesses a web service, then I thought I would create my own "WebServiceException", which would be created in the data access layer whenever an HttpException, WebException or SoapException is thrown. So now, generally I will be catching 2 or 3 exceptions where currently I catch just the general Exception, and I think that seems OK to me. Does anyone wrap exceptions up again to carry the message up to the presentation layer? I think I should probably add a try catch to Main() that catches Exception, attempts to log it, displays an "Application has encountered an error" message and exits the application. So, my question is, does anyone see any holes in my plan? Are there any obvious exceptions that I should be catching or do these ones pretty much cover it (other than file access - I think there is only 1 place where we read-write to a config file).

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  • Using C Structs which contains ObjC Objects?

    - by GuidoMB
    I'm using C structs in objc and I've created a function that assembles the structure like the one from the Cocoa API. The things is that this structure is not like NSRect o NSPoint this structure packs objc objects soo I'm seeing a potential memory leak here. Do I need to provide a function to 'release' the structure? I'am not creating a ISKNewsCategory class because there will be no behavior but Do you think this is a good approach or I should define the class even doe there will be no behavior? typedef struct ISK_NewsCategory { NSString *name; NSString *code } ISKNewsCategory; NS_INLINE ISKNewsCategory ISKMakeNewsCategory(NSString *name, NSString *code) { ISKNewsCategory category; category.name = [name retain]; category.code = [code retain]; return category; }

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  • effective retrieve for a voting system in PHP

    - by Adnan
    Hello, I have a system where registered users can vote up/vote down comment for a picture. Something very similar to SO's voting system. I store the votes in a table with values as such; vote_id | vote_comment_id | vote_user_id | vote_date Now I have few a question concerned the speed and efficiency for the following; PROB: Once a user opens the picture page with comments I need, if that user has already voted UP/DOWN a comment to show it like; "you voted up" or "you voted down" next to the comment (in SO it the vote image is highlighted) MY POSSIBLE SOL: Right now when I open a picture page for each comment I loop thru, I loop thru my table of votes as well and check if a user has voted and show the status (I compare the vote_user_id with the user's session). How efficient is this? Anyone have a better approach to tackle this kind of problem?

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  • Is there a way to avoid debugger?

    - by Gabriel Šcerbák
    I don't like debugging in a debugger, because I think it is often below the abstraction layer of the programming language and it is often not reproducible. I favor usign unit tests when possible and I think they are a good way, but it is not always that easy to implement them. Do you know about any other alternative approaches to avoid the use of debugger?

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  • New design patterns/design strategies

    - by steven
    I've studied and implemented design patterns for a few years now, and I'm wondering. What are some of the newer design patterns (since the GOF)? Also, what should one, similar to myself, study [in the way of software design] next? Note: I've been using TDD, and UML for some time now. I'm curious about the newer paradigm shifts, and or newer design patterns.

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  • What is best practice with SQLite and Android ?

    - by PHP_Jedi
    What is considered "best practice" when executing queries on a sql-lite db within an android app. Is it safe to run inserts, deletes and select queries from an AsyncTask's doInBackground ? Or should I use the UI Thread ? I suppose that db queries can be "heavy" and should not use the UI thread as it can lock up the app - resulting in an ANR. If I have several AsyncTasks, should they share a connection or should they open a connection each ? Any best practices in this area on android?

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  • Which layer should create DataContext?

    - by Kevin
    I have a problem to decide which layer in my system should create DataContext. I have read a book, saying that if do not pass the same DataContext object for all the database updates, it will sometimes get an exception thrown from the DataContext. That's why i initially create new instance of DataContext in business layer, and pass it into data access layer. So that the same datacontext is used for all the updates. But this lead to one design problem, if i wanna change my DAL to Non-LinqToSQL in future, i need to re-write the code in business layer as well. Please give me some advice on this. Thanks. Example code 'Business Layer Public Sub SaveData(name As String) Using ts AS New TransactionScope() Using db As New MyDataContext() DAL.Insert(db,name) DAL.Insert(db,name) End Using ts.Complete() End Using End Sub 'Data Access Layer Public Sub Insert(db as MyDataContext,name As string) db.TableAInsert(name) End Sub

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  • To HTML 5 or not to HTML 5 ?

    - by ZX12R
    I am a designer whose main marketing strategy is multi browser compatibility. I assure my clients that the site will work even in IE6 (!). Of late i have been pondering over the question of moving to HTML 5. The reason behind my apprehension is that IE6 is still a major player in terms of market share and i don't want to lose it. Is there any way of moving to HTML 5 and still promise multi browser compatibility? Thank you.

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  • Why avoid increment ("++") and decrement ("--") operators in JavaScript?

    - by artlung
    I'm a big fan of Douglas Crockford's writing on JavaScript, particularly his book JavaScript: The Good Parts. It's made me a better JavaScript programmer and a better programmer in general. One of his tips for his jslint tool is this : ++ and -- The ++ (increment) and -- (decrement) operators have been known to contribute to bad code by encouraging excessive trickiness. They are second only to faulty architecture in enabling to viruses and other security menaces. There is a plusplus option that prohibits the use of these operators. This has always struck my gut as "yes, that makes sense," but has annoyed me when I've needed a looping condition and can't figure out a better way to control the loop than a while( a < 10 )do { a++ } or for (var i=0;i<10;i++) { } and use jslint. It's challenged me to write it differently. I also know in the distant past using things, in say PHP like $foo[$bar++] has gotten me in trouble with off-by-one errors. Are there C-like languages or other languages with similarities that that lack the "++" and "--" syntax or handle it differently? Are there other rationales for avoiding "++" and "--" that I might be missing? UPDATE -- April 9, 2010: In the video Crockford on JavaScript -- Part 5: The End of All Things, Douglas Crockford addresses the ++ issue more directly and with more detail. It appears at 1:09:00 in the timeline. Worth a watch.

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  • Is it naughty to have a large utility file?

    - by banister
    In my C project I have quite a large utils.c file. It is really full of many utilities of different sorts. I feel a bit naughty just stuffing different miscellaneous functions in there. For example it has some utilities related to low level stuff such as a lowercase() function, and it also has some quite sophisticated utilities such as converting to/from different colour formats. My question is, is it very naughty to have such a large utils.c with many different types of utilities in it? Should I break it up into many different kinds of utility files? Such as graphics_utils.c and so on What do you think?

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  • Explaining the need to avoid horizontal scroll

    - by Bradley Herman
    I need help explaining to my boss why her design is poor on a client's website. She has no knowledge of the web, and it can be difficult as a web developer working with a woman who is a graphic designer (not even a web designer really). On a current site she has designed, an image bar "needs" to be ~1200px according to her, though it isn't necessary with the content. A quick sketch to illustrate what's going on: As you see, the banner spills out past the 960px of the content and as wide as 1200px. This creates a horizontal scroll when all the content is viewable within the 960px wide viewport. I need to make this an <img and not a CSS background because it's a jQuery slideshow that fades from image to image. I think this is a big problem because a lot of people are going to get a horizontal scroll bar imposed in their browser when they're still able to see all the relevant content. She thinks no one will notice and it'll be fine; I think it's very bad practice and confusing to the end user. How do I explain the problem to her?

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  • Multi-tenant Access Control: Repository or Service layer?

    - by FreshCode
    In a multi-tenant ASP.NET MVC application based on Rob Conery's MVC Storefront, should I be filtering the tenant's data in the repository or the service layer? 1. Filter tenant's data in the repository: public interface IJobRepository { IQueryable<Job> GetJobs(short tenantId); } 2. Let the service filter the repository data by tenant: public interface IJobService { IList<Job> GetJobs(short tenantId); } My gut-feeling says to do it in the service layer (option 2), but it could be argued that each tenant should in essence have their own "virtual repository," (option 1) where this responsibility lies with the repository. Which is the most elegant approach: option 1, option 2 or is there a better way? Update: I tried the proposed idea of filtering at the repository, but the problem is that my application provides the tenant context (via sub-domain) and only interacts with the service layer. Passing the context all the way to the repository layer is a mission. So instead I have opted to filter my data at the service layer. I feel that the repository should represent all data physically available in the repository with appropriate filters for retrieving tenant-specific data, to be used by the service layer. Final Update: I ended up abandoning this approach due to the unnecessary complexities. See my answer below.

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  • More pythonic way to iterate

    - by fmark
    I am using a module that is part of a commercial software API. The good news is there is a python module - the bad news is that its pretty unpythonic. To iterate over rows, the follwoing syntax is used: cursor = gp.getcursor(table) row = cursor.Next() while row: #do something with row row = cursor.next() What is the most pythonic way to deal with this situation? I have considered creating a first class function/generator and wrapping calls to a for loop in it: def cursor_iterator(cursor): row = cursor.Next() while row: yield row row = cursor.next() [...] cursor = gp.getcursor(table) for row in cursor_iterator(cursor): # do something with row This is an improvement, but feels a little clumsy. Is there a more pythonic approach? Should I create a wrapper class around the table type?

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  • comparator with null values.

    - by pvgoddijn
    Hi, We have some code wich sorts a list of addresses based on the distance between their coordinates. this is done through collections.sort with a custom comparator. However from time to time an adress without coordinates is in the list causing a NullPointerException. My initial idea to fix this was to have the comparator return 0 as dististance for addresses where at least one of the coordinates is null. I fear this might lead to corruption of the order the 'valid' elements in the list. so is returning a '0' values for null data in a comparator ok, or is there a cleaner way to resolve this.

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  • How to control respond_to based on variable in Rails controller?

    - by smotchkkiss
    The dilemma I'm using a before_filter in my controller that restricts access to admins. However, I want to allow access public access to some methods based on request format. See the index method to understand what I'm talking about. items_controller.rb class ItemsController < ApplicationController before_filter :superuser_required layout 'superuser' def index @items = Item.all respond_to do |format| format.html format.js # I want public to have access to this end end def show @item = Item.find(params[:id]) respond_to do |format| format.html end end def new @item = Item.new respond_to do |format| format.html end end # remaining controller methods # ... def superuser_required redirect_to login_path unless current_user.superuser? end end

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  • What is the best practice for writing bookmarklets

    - by Ritesh M Nayak
    I am writing some bookmarklets for a project that I am currently working on and I was wondering what the best practice for writing a bookmarklet was. I did some looking around and this is what I came up with javascript:void((function() { var%20e=document.createElement('script'); e.setAttribute('type','text/javascript'); e.setAttribute('src','http://someserver.com/bookmarkletcode.js'); document.body.appendChild(e) })()) I felt this is nice because the code can always be changed (since its requested every time) and still it acts like a bookmarklet. Are there are any problems to this approach ? Browser incompatibility etc? What is the best practice for this?

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  • How to connect remote EJB module from application client

    - by Zeck
    Hi guys, I have a EJB module in remote Glassfish server and application client in my computer. I want to connect from the application client to the remote EJB. Here is the my EJB interface: @Remote public interface BookEJBRemote { public String getTitle(); } Here is the my ejb: @Stateless public class BookEJB implements BookEJBRemote { @Override public String getTitle() { return "Twenty Thousand Leagues Under the Sea"; } } I have several questions : Can I use Dependency Injection in the remote application client to connect to the ejb? If so what can i do to achieve this. Do i need to configure in the sun-ejb-jar.xml and sun-application-client.xml? In other words, if i use DI like @EJB MyEJBRemote ejb; How application client container know what ejb to be injected? Where should i specify the information? How can i run the application client? I tried to run package-appclient in the glassfish server to get appclient.jar and copy it to my computer. Then i type appclient.jar -client myAppClient.jar . It didn't work. How do i point the target server? if i cannot use DI in the client then i guess i have to use JNDI lookup. Do i need to configure jndi name in sun-ejb-jar.xml or in the sun-application-client.xml? No matter how i try i never manage to run application client ? Can you guys put some working example? And thank you for every advises and examples?

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