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  • Why is using a common-lookup table to restrict the status of entity wrong?

    - by FreshCode
    According to Five Simple Database Design Errors You Should Avoid by Anith Sen, using a common-lookup table to store the possible statuses for an entity is a common mistake. Why is this wrong? I disagree that it's wrong, citing the example of jobs at a repair service with many possible statuses that generally have a natural flow, eg.: Booked In Assigned to Technician Diagnosing problem Waiting for Client Confirmation Repaired & Ready for Pickup Repaired & Couriered Irreparable & Ready for Pickup Quote Rejected Arguably, some of these statuses can be normalised to tables like Couriered Items, Completed Jobs and Quotes (with Pending/Accepted/Rejected statuses), but that feels like unnecessary schema complication. Another common example would be order statuses that restrict the status of an order, eg: Pending Completed Shipped Cancelled Refunded The status titles and descriptions are in one place for editing and are easy to scaffold as a drop-down with a foreign key for dynamic data applications. This has worked well for me in the past. If the business rules dictate the creation of a new order status, I can just add it to OrderStatus table, without rebuilding my code.

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  • HTTP headers: Last-Modified - how can it mimimize server load?

    - by gotts
    Imagine the following use case: I use an AJAX request for getting some info about Item and use this URL: http://domain/items/show/1 In my database all items have a field called modified_at where we store the moment when this item was previously modified. How can Last-Modified server HTTP header in response can minimize load/reduce requests/increase responsiveness if we need to process this request every time on the server side? It looks like we don't reduce the number of HTTP requests with that response and we don't reduce the load on server. Who needs this anyway?

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  • SQL Server error handling: exceptions and the database-client contract

    - by gbn
    We’re a team of SQL Servers database developers. Our clients are a mixed bag of C#/ASP.NET, C# and Java web services, Java/Unix services and some Excel. Our client developers only use stored procedures that we provide and we expect that (where sensible, of course) they treat them like web service methods. Some our client developers don’t like SQL exceptions. They understand them in their languages but they don’t appreciate that the SQL is limited in how we can communicate issues. I don’t just mean SQL errors, such as trying to insert “bob” into a int column. I also mean exceptions such as telling them that a reference value is wrong, or that data has already changed, or they can’t do this because his aggregate is not zero. They’d don’t really have any concrete alternatives: they’ve mentioned that we should output parameters, but we assume an exception means “processing stopped/rolled back. How do folks here handle the database-client contract? Either generally or where there is separation between the DB and client code monkeys. Edits: we use SQL Server 2005 TRY/CATCH exclusively we log all errors after the rollback to an exception table already we're concerned that some of our clients won't check output paramaters and assume everything is OK. We need errors flagged up for support to look at. everything is an exception... the clients are expected to do some message parsing to separate information vs errors. To separate our exceptions from DB engine and calling errors, they should use the error number (ours are all 50,000 of course)

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  • Are there any downsides in using C++ for network daemons?

    - by badcat
    Hey guys! I've been writing a number of network daemons in different languages over the past years, and now I'm about to start a new project which requires a new custom implementation of a properitary network protocol. The said protocol is pretty simple - some basic JSON formatted messages which are transmitted in some basic frame wrapping to have clients know that a message arrived completely and is ready to be parsed. The daemon will need to handle a number of connections (about 200 at the same time) and do some management of them and pass messages along, like in a chat room. In the past I've been using mostly C++ to write my daemons. Often with the Qt4 framework (the network parts, not the GUI parts!), because that's what I also used for the rest of the projects and it was simple to do and very portable. This usually worked just fine, and I didn't have much trouble. Being a Linux administrator for a good while now, I noticed that most of the network daemons in the wild are written in plain C (of course some are written in other languages, too, but I get the feeling that 80% of the daemons are written in plain C). Now I wonder why that is. Is this due to a pure historic UNIX background (like KISS) or for plain portability or reduction of bloat? What are the reasons to not use C++ or any "higher level" languages for things like daemons? Thanks in advance! Update 1: For me using C++ usually is more convenient because of the fact that I have objects which have getter and setter methods and such. Plain C's "context" objects can be a real pain at some point - especially when you are used to object oriented programming. Yes, I'm aware that C++ is a superset of C, and that C code is basically C++. But that's not the point. ;)

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  • Java: Make a method abstract for each extending class

    - by Martijn Courteaux
    Hi, Is there any keyword or design pattern for doing this? public abstract class Root { public abstract void foo(); } public abstract class SubClass extends Root { public void foo() { // Do something } } public class SubberClass extends SubClass { // Here is it not necessary to override foo() // So is there a way to make this necessary? // A way to obligate the developer make again the override } Thanks

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  • Robust Large File Transfer with WCF

    - by Sharov
    I want to transfer big files (1GB) over unreliable transport channels. When connection is interrupted, I don't want start file transfering from the begining. I can partially store it in a temp table and store last readed position, so when connection is reestablished I can request continue uploading of file from this position. Is there any best-practice for such kind of things. I'm currently use chunking channel.

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  • Where do you extend classes in your rails application?

    - by ro
    Just about to extend the Array class with the following extension: class Array def shuffle! size.downto(1) { |n| push delete_at(rand(n)) } self end end However, I was wondering where a good place to keep these sort of extensions. I was thinking environment.rb or putting in its own file in the initializers directory.

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  • DOs and DON'Ts of a technical presentation

    - by TG
    I am preparing a technical presentation for my team. Audience : Our team Topic : Introduction to a new technology So I want to know about the primary necessary things for a good technical presentation and also DOs and DON'Ts for the same. some of my concerns are, 1. Whether to have slides or not (if needed then how many of them) 2. Coding a sample during presentation or preparing it before going for the presentation 3. Maximum duration of an technical presentation What is your thoughts on technical presentations from your past experience either as a presenter or as a listener.

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  • UX Design Question: Should a multi step wizard save the form contents when the user clicks 'go back'

    - by Ashwin Prabhu
    I am developing a web application that collects data over multiple steps through a wizard. Steps are generally not interdependent, in that data input at each step has little or no effect on the consequent steps. However each step may have a set of validations which determine whether the user can progress to the next step by clicking 'continue' What should be the behavior when the user clicks previous? a Quickly move to the previous page, thus losing all the unsaved data in the form. Prompting the user with a warning is an option, but it can become irritating quite soon. b Move to the previous page saving all the data in the current step - without triggering validations, so that when the user comes back she sees the form in the same state that she left it in. c any other behaviour All opinions are welcome :)

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  • Question about the benefit of using an ORM

    - by johnny
    I want to use an ORM for learning purposes and am try nhibernate. I am using the tutorial and then I have a real project. I can go the "old way" or use an ORM. I'm not sure I totally understand the benefit. On the one hand I can create my abstractions in code such that I can change my databases and be database independent. On the other it seems that if I actually change the database columns I have to change all my code. Why wouldn't I have my application without the ORM, change my database and change my code, instead of changing my database, orm, and code? Is it that they database structure doesn't change that much? I believe there are real benefits because ORMs are used by so many. I'm just not sure I get it yet. Thank you. EDIT: In the tutorial they have many files that are used to make the ORM work http://www.hibernate.org/362.html In the event of an application change, it seems like a lot of extra work just to say that I have "proper" abstraction layers. Because I'm new at it it doesn't look that easy to maintain and again seems like extra work, not less.

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  • Looking for design help

    - by jess
    I have this scenario in most of the WindowsForms having grids I have a sequence of code which is similar - AddNewRow(in grid),CreateNewEntity,notifyUser,few other steps Now, I want to use a template kind of pattern.But,my issue is with CreateEntity method since sometimes it is passed a parameter which is different depending on the type of object being created.Should I make createentity accept an "object" type,and cast when the parameter is to be used.What other way can I tackle this design issue? Also,CreateEntity returns the object being created.

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  • .net design pattern question

    - by user359562
    Hi. I am trying to understand design pattern problems. I am trying to modify the code like this in winforms and trying to see if any design pattern suits my requirement. Please suggest which is the best design pattern in this scenario. This is very basic code containing 2 tab pages which might have different controls can be added dynamically and read out different files on click of particular tab. To elaborate more... I have written this code to learn and understand design pattern. This is just a scenario where user click on a particular tab which will show dynamic controls generated. public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void tabControl1_SelectedIndexChanged(object sender, EventArgs e) { if (tabControl1.SelectedTab.Name.Equals("tabPage1")) { GeneratedynamicControlsForTab1(); } else if (tabControl1.SelectedTab.Name.Equals("tabPage2")) { GeneratedynamicControlsForTab2(); } } private void GeneratedynamicControlsForTab1() { Label label1 = new Label(); label1.Text = "Label1"; tabPage1.Controls.Add(label1); ReadCSVFile(); } private void GeneratedynamicControlsForTab2() { tabPage1.Controls.Clear(); Label label2 = new Label(); label2.Text = "Label2"; tabPage2.Controls.Add(label2); ReadTextFile(); } private void ReadCSVFile() { } private void ReadTextFile() { } }

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  • standard debugging way for javascript/jquery

    - by ZX12R
    This is my usual way to debug javascript. Include alert(0); to break the flow and find out what is happening. sometimes when i need multiple check points i do alert('the flow is now in function 1'); alert('the flow is now in function 2'); or sometimes just alert('success'); i would like to know if there is any standard way for debugging adopted as i am finding my current method very intrusive. thanks in advance..:)

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  • Scrum backlog sizing is taking forever

    - by zachary
    I work on a huge project. While we program we end up meeting for endless backlog sizing sessions where all the developers sit down with the team and size user stories. Scrum doubters are saying that this process is taking too long and development time is being wasted. My question is how long should it take to size a user story on average? And does anyone have any tips to make these sizing sessions go quicker?

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  • What are the principles of developing web-applications with action-based java frameworks?

    - by Roman
    Background I'm going to develop a new web-application with java. It's not very big or very complex and I have enough time until it'll "officially" start. I have some JSF/Facelets development background (about half a year). And I also have some expirience with JSP+JSTL. In self-educational purpose (and also in order to find the best solution) I want to prototype the new project with one of action-based frameworks. Actually, I will choose between Spring MVC and Stripes. Problem In order to get correct impression about action-based frameworks (in comparison with JSF) I want to be sure that I use them correctly (in bigger or lesser extent). So, here I list some most-frequent tasks (at least for me) and describe how I solve them with JSF. I want to know how they should be solved with action-based framework (or separately with Spring MVC and Stripes if there is any difference for concrete task). Rendering content: I can apply ready-to-use component from standard jsf libraries (core and html) or from 3rd-party libs (like RichFaces). I can combine simple components and I can easily create my own components which are based on standard components. Rendering data (primitive or reference types) in the correct format: Each component allow to specify a converter for transforming data in both ways (to render and to send to the server). Converter is, as usual, a simple class with 2 small methods. Site navigation: I specify a set of navigation-cases in faces-config.xml. Then I specify action-attribute of a link (or a button) which should match one or more of navigation cases. The best match is choosen by JSF. Implementing flow (multiform wizards for example): I'm using JSF 1.2 so I use Apache Orchestra for the flow (conversation) scope. Form processing: I have a pretty standard java-bean (backing bean in JSF terms) with some scope. I 'map' form fields on this bean properties. If everything goes well (no exceptions and validation is passed) then all these properties are set with values from the form fields. Then I can call one method (specified in button's action attribute) to execute some logic and return string which should much one of my navigation cases to go to the next screen. Forms validation: I can create custom validator (or choose from existing) and add it to almost each component. 3rd-party libraries have sets of custom ajax-validators. Standard validators work only after page is submitted. Actually, I don't like how validation in JSF works. Too much magic there. Many standard components (or maybe all of them) have predefined validation and it's impossible to disable it (Maybe not always, but I met many problems with it). Ajax support: many 3rd-party libraries (MyFaces, IceFaces, OpenFaces, AnotherPrefixFaces...) have strong ajax support and it works pretty well. Until you meet a problem. Too much magic there as well. It's very difficult to make it work if it doesn't work but you've done right as it's described in the manual. User-friendly URLs: people say that there are some libraries for that exist. And it can be done with filters as well. But I've never tried. It seems too complex for the first look. Thanks in advance for explaning how these items (or some of them) can be done with action-based framework.

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  • How to Communicate between minifb and a GAE-Hosted Silverlight Client

    - by Nick Gotch
    I have a minifb app (technically gminifb) running on Google App Engine with a bunch of handlers for processing all kinds of requests from a Silverlight client. What's the recommended approach for adding the FB GET variables, such as fb_sig, to the HTTP requests? I believe I can technically pass the session key and uid directly and get things to work but it seems there's probably a much better way to do this. I was reading about FBJS AJAX and I'm trying to figure out how I can use it to proxy the HTTP requests from the Silverlight client through it. Is this a good way to do it? And if so, how would I go about doing so? Any other recommendations would be appreciated too. Thanks,

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  • How to corelate gtk.ListStore items with my own models

    - by Victor Stanciu
    Hello, I have a list of Project objects, that I display in a GTK TreeView. I am trying to open a dialog with a Project's details when the user double-clicks on the item's row in the TreeView. Right now I get the selected value from the TreeView (which is the name of the Project) via get_selection(), and search for that Project by name in my own list to corelate the selection with my own model. However, this doesn't feel quite right (plus, it assumes that a Project's name is unique), and I was wondering if there is a more elegant way of doing it.

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  • Inheritance in tables - structure problem

    - by Naor
    I have 3 types of users in my system. each type has different information I created the following tables: BaseUser(base_user_id, username, password, additional common data) base_user_id is PK and Identity UserType1(user_id, data related to type1 only) user_id is PK and FK to base_user_id UserType2(user_id, data related to type2 only) user_id is PK and FK to base_user_id UserType3(user_id, data related to type3 only) user_id is PK and FK to base_user_id Now I have relation from each type of user to warehouses table. Users from type1 and type2 should have only warehouse_id and users from type3 should have warehouse_id and customer_id. I thought about this structure: WarehouseOfUser(base_user_id,warehouse_id) base_user_id is FK to base_user_id in BaseUser WarehouseOfTyp3User(base_user_id,warehouse_id, customer_id) base_user_id is FK to base_user_id in BaseUser The problem is that such structure allows 2 things I want to prevent: 1. add to WarehouseOfTyp3User data of user from type2 or type1. 2. add to WarehouseOfUser data of user from type3. what is the best structure for such case?

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  • Process for beginning a Ruby on Rails project

    - by Daniel Beardsley
    I'm about to begin a Ruby on Rails project and I'd love to hear how others go through the process of starting an application design. I have quite a bit of experience with RoR, but don't have that many starting from scratch with only a vision experiences and would appreciate the wisdom of others who've been there. I'm looking for an order of events, reasons for the order, and maybe why each part is important. I can think of a few starting points, but I'm not sure where it's best to begin Model design and relationships (entities, how they relate, and their attributes) Think of user use-cases (or story-boards) and implement the minimum to get these done Create Model unit-tests then create the necessary migrations and AR models to get the tests to pass Hack out the most basic version of the simplest part of your application and go from there Start with a template for a rails app (like http://github.com/thoughtbot/suspenders) Do the boring gruntwork first (User auth, session management, ...) ...

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  • WPF binding to a boolean on a control

    - by Jose
    I'm wondering if someone has a simple succinct solution to binding to a dependency property that needs to be the converse of the property. Here's an example I have a textbox that is disabled based on a property in the datacontext e.g.: <TextBox IsEnabled={Binding CanEdit} Text={Binding MyText}/> The requirement changes and I want to make it ReadOnly instead of disabled, so without changing my ViewModel I could do this: In the UserControl resources: <UserControl.Resources> <m:NotConverter x:Key="NotConverter"/> </UserControl.Resources> And then change the TextBox to: <TextBox IsReadOnly={Binding CanEdit,Converter={StaticResource NotConverter}} Text={Binding MyText}/> Which I personally think is EXTREMELY verbose I would love to be able to just do this(notice the !): <TextBox IsReadOnly={Binding !CanEdit} Text={Binding MyText}/> But alas, that is not an option that I know of. I can think of two options. Create an attached property IsNotReadOnly to FrameworkElement(?) and bind to that property If I change my ViewModel then I could add a property CanEdit and another CannotEdit which I would be kind of embarrassed of because I believe it adds an irrelevant property to a class, which I don't think is a good practice. The main reason for the question is that in my project the above isn't just for one control, so trying to keep my project as DRY as possible and readable I am throwing this out to anyone feeling my pain and has come up with a solution :)

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  • Can i change the view without changing the controller?

    - by Ian Boyd
    Pretend1 there is a place to type in a name:     Name: __________________ When the text box changes, the value is absorbed into the controller, who stores it in data model. Business rules require that a name be entered: if there is no text entered the TextBox should be colored something in the view to indicate baddness; otherwise it can be whatever color the view likes. The TextBox contains a String, the controller handles a String, and the model stores a String. Now lets say i want to improve the view. There is a new kind of text box2 that can be fed not only string-based keyboard input, but also an image. The view (currently) knows how to determine if the image is in the proper format to perform the processing required to extract text out of it. If there is text, then that text can be fed to the controller, who feeds it to the data model. But if the image is invalid, e.g.3 wrong file format invalid dimensions invalid bit depth unhandled or unknown encoding format missing or incorrectly located registration marks contents not recognizable the view can show something to the user that the image is bad. But the telling the user that something is bad is supposed to be the job of the controller. i'm, of course, not going to re-write the controller to handle Image based text-input (e.g. image based names). a. the code is binary locked inside a GUI widget4 b. there other views besides this one, i'm not going to impose a particular view onto the controller c. i just don't wanna. If i have to change things outside of this UI improvement, then i'll just leave the UI unimproved5 So what's the thinking on having different views for the same Model and Controller? Nitpicker's Corner 1 contrived hypothetical example 2 e.g. bar code, g-mask, ocr 3 contrived hypothetical reasons 4 or hardware of a USB bar-code scanner 5 forcing the user to continue to use a DateTimePicker rather than a TextBox

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  • Process a batch of items, return an object to report on status

    - by Naeem Sarfraz
    I'm looking for a pattern (or good practice) for the following scenario: My function List<BatchItemResponse> Process(List<BatchItem> Data) {..} will process a list of data, and return info on where each item in the batch could be processed. struct BatchItemResponse { int BatchItemID; bool Processed; string Description; } Any thoughts? Is what I've proposed as good as it gets?

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