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  • mysql unique-constraint

    - by Cypher
    I have two tables -- Variables (id, name) and Variable_Entries (id, var_id, value). I want each variable to have a unique set of entries. If I make the value entry unique then a different variable won't be able to have that same value which is not right. Is there some way to make the value column unique for identical var_id's?

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  • Examples of IOC/DI over Singleton

    - by Amitd
    Hi, Just started learning/reading about DI and IOC frameworks. Also I read many articles on SO and internet that say that one should prefer DI/IOC over singleton. Can anyone give/link examples of exactly how DI/IOC eliminates/solves the various issues regarding the Singleton pattern? (hopefully code and explanation for better understanding) Also given a system has already implemented Singleton pattern, how to refactor/implement DI/IOC for the same? (any examples for the same?) (Language/Framework no bars..C# would be helpful) Thanks

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  • Any sample C# project that highlights separate data access layer (using EF) to business logic layer

    - by Greg
    Hi, I'm interested in having a look at a small sample project that would highlight a good technique to separate data access layer (using Entity Framework) to business logic layer. In C# would be good. That is, it would highlight how to pass data between the layer without coupling them. That is, the assumption here is not to use the EF classes in the Business Logic layer, and how to achieve this low coupling, but minimizing plumbing code.

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  • Example of a Good Func Spec?

    - by Alex
    Hey, I'm writing my func spec, and I was wondering if there are any good samples of a complete and well-written func spec? Like "This is a standard You're supposed to aspire to" type of spec. I know that Joel has a skeleteon of a func spec on his website, but I am looking for something more complete because I'm not of the appropriate amount of detail, formatting, etc. Thanks, Alex

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  • Best method to store Enum in Database

    - by LnDCobra
    What is the best method of storing an Enum in a Database using C# And Visual Studio and MySQL Data Connector. I am going to be creating a new project with over 100 Enums, and majority of them will have to be stored in the database. Creating converters for each one would be a long winded process therefore I'm wondering if visual studio or someone has any methods for this that I haven't heard off.

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  • When writing a game, should you make objects/enemies/etc. have unique ID numbers?

    - by SLC
    I have recently encountered some issues with merely passing references to objects/enemies in a game I am making, and am wondering if I am using the wrong approach. The main issue I have is disposing of enemies and objects, when other enemies or players may still have links to them. For example, if you have a Rabbit, and a Wolf, the Wolf may have selected the Rabbit to be its target. What I am doing, is the wolf has a GameObject Target = null; and when it decides it is hungry, the Target becomes the Rabbit. If the Rabbit then dies, such as another wolf killing it, it cannot be removed from the game properly because this wolf still has a reference to it. In addition, if you are using a decoupled approach, the rabbit could hit by lightning, reducing its health to below zero. When it next updates itself, it realises it has died, and is removed from the game... but there is no way to update everything that is interested in it. If you gave every enemy a unique ID, you could simply use references to that instead, and use a central lookup class that handled it. If the monster died, the lookup class could remove it from its own index, and subsequently anything trying to access it would be informed that it's dead, and then they could act accordingly. Any thoughts on this?

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  • Reuse nib's across multiple UIViewControllers

    - by colm
    I've created some custom UITableViewCells in a nib file and would like to use that across multiple UIViewControllers. Can anyone tell me the best practice way to do that? My limited knowledge around loading nibs seems to suggest that you have to specify a single owner class in Interface Builder. Thanks.

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  • Daylight saving time - do and don'ts

    - by Oded
    I am hoping to make this question and the answers to it the definitive guide to dealing with daylight saving time, in particular for dealing with the actual change overs. Many systems are dependent on keeping accurate time, the problem is with changes to time due to daylight savings - moving the clock forward or backwards. For instance, one has business rules in an order taking system that depend on the time of the order - if the clock changes, the rules might not be as clear. How should the time of the order be persisted? There is of course an endless number of scenarios - this one is simply an illustrative one. How have you dealt with the daylight saving issue? What assumptions are part of your solution? (looking for context here) As important, if not more so: What did you try that did not work? Why did it not work? I would be interested in programming, OS, data persistence and other pertinent aspects of the issue. General answers are great, but I would also like to see details especially if they are only available on one platform.

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  • How should I provide access to this custom DAL?

    - by Casey
    I'm writing a custom DAL (VB.NET) for an ordering system project. I'd like to explain how it is coded now, and receive some alternate ideas to make coding against the DAL easier/more readable. The DAL is part of an n-tier (not n-layer) application, where each tier is in it's own assembly/DLL. The DAL consists of several classes that have specific behavior. For instance, there is an Order class that is responsible for retrieving and saving orders. Most of the classes have only two methods, a "Get" and a "Save," with multiple overloads for each. These classes are marked as Friend and are only visible to the DAL (which is in it's own assembly). In most cases, the DAL returns what I will call a "Data Object." This object is a class that contains only data and validation, and is located in a common assembly that both the BLL and DAL can read. To provide public access to the DAL, I currently have a static (module) class that has many shared members. A simplified version looks something like this: Public Class DAL Private Sub New End Sub Public Shared Function GetOrder(OrderID as String) as OrderData Dim OrderGetter as New OrderClass Return OrderGetter.GetOrder(OrderID) End Function End Class Friend Class OrderClass Friend Function GetOrder(OrderID as string) as OrderData End Function End Class The BLL would call for an order like this: DAL.GetOrder("123456") As you can imagine, this gets cumbersome very quickly. I'm mainly interested in structuring access to the DAL so that Intellisense is very intuitive. As it stands now, there are too many methods/functions in the DAL class with similar names. One idea I had is to break down the DAL into nested classes: Public Class DAL Private Sub New End Sub Public Class Orders Private Sub New End Sub Public Shared Function Get(OrderID as string) as OrderData End Function End Class End Class So the BLL would call like this: DAL.Orders.Get("12345") This cleans it up a bit, but it leaves a lot of classes that only have references to other classes, which I don't like for some reason. Without resorting to passing DB specific instructions (like where clauses) from BLL to DAL, what is the best or most common practice for providing a single point of access for the DAL?

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  • Is it possible to create static classes in PHP (like in C#)?

    - by aleemb
    I want to create a static class in PHP and have it behave like it does in C#, so Constructor is automatically called on the first call to the class No instantiation required Something of this sort... static class Hello { private static $greeting = 'Hello'; private __construct() { $greeting .= ' There!'; } public static greet(){ echo $greeting; } } Hello::greet(); // Hello There!

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  • Making a DateTime field in SQLExpress database?

    - by Mike
    I'm putting together a simple test database to learn MVC with. I want to add a DateTime field to show when the record was CREATED. ID = int Name = Char DateCreated = (dateTime, DateTime2..?) I have a feeling that this type of DateTime capture can be done automatically - but that's all I have, a feeling. Can it be done? And if so how? While we're on the subject: if I wanted to include another field that captured the DateTime of when the record was LAST UPDATED how would I do that. I'm hoping to not do this manually. Many thanks Mike

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  • Are web-safe colors still relevant?

    - by Gavin Miller
    Since the vast majority of monitors are 16-bit color or more, including mobile devices, does it make sense to even consider web-safe colors when choosing color schemes? Or is it something that ought to be relegated to history as a piece of trivia? For those of you that don't know what web-safe colors are: Another set of 216 color values is commonly considered to be the "web-safe" color palette, developed at a time when many computer displays were only capable of displaying 256 colors. A set of colors was needed that could be shown without dithering on 256-color displays; the number 216 was chosen partly because computer operating systems customarily reserved sixteen to twenty colors for their own use; it was also selected because it allows exactly six shades each of red, green, and blue (6 × 6 × 6 = 216). The list of colors is often presented as if it has special properties that render them immune to dithering. In fact, on 256-color displays applications can set a palette of any selection of colors that they choose, dithering the rest. These colors were chosen specifically because they matched the palettes selected by the then leading browser applications. [Wikipedia]

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  • XAML Binding to complex value objects

    - by Gus
    I have a complex value object class that has 1) a number or read-only properties; 2) a private constructor; and 3) a number of static singleton instance properties [so the properties of a ComplexValueObject never change and an individual value is instantiated once in the application's lifecycle]. public class ComplexValueClass { /* A number of read only properties */ private readonly string _propertyOne; public string PropertyOne { get { return _propertyOne; } } private readonly string _propertyTwo; public string PropertyTwo { get { return _propertyTwo; } } /* a private constructor */ private ComplexValueClass(string propertyOne, string propertyTwo) { _propertyOne = propertyOne; _propertyTwo = PropertyTwo; } /* a number of singleton instances */ private static ComplexValueClass _complexValueObjectOne; public static ComplexValueClass ComplexValueObjectOne { get { if (_complexValueObjectOne == null) { _complexValueObjectOne = new ComplexValueClass("string one", "string two"); } return _complexValueObjectOne; } } private static ComplexValueClass _complexValueObjectTwo; public static ComplexValueClass ComplexValueObjectTwo { get { if (_complexValueObjectTwo == null) { _complexValueObjectTwo = new ComplexValueClass("string three", "string four"); } return _complexValueObjectTwo; } } } I have a data context class that looks something like this: public class DataContextClass : INotifyPropertyChanged { private ComplexValueClass _complexValueClass; public ComplexValueClass ComplexValueObject { get { return _complexValueClass; } set { _complexValueClass = value; PropertyChanged(this, new PropertyChangedEventArgs("ComplexValueObject")); } } } I would like to write a XAML binding statement to a property on my complex value object that updates the UI whenever the entire complex value object changes. What is the best and/or most concise way of doing this? I have something like: <Object Value="{Binding ComplexValueObject.PropertyOne}" /> but the UI does not update when ComplexValueObject as a whole changes.

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  • Single value data to multiple values of data in database relation

    - by Sofiane Merah
    I have such a hard time picturing this. I just don't have the brain to do it. I have a table called reports. --------------------------------------------- | report_id | set_of_bads | field1 | field2 | --------------------------------------------- | 123 | set1 | qwe | qwe | --------------------------------------------- | 321 | 123112 | ewq | ewq | --------------------------------------------- I have another table called bads. This table contains a list of bad data. ------------------------------------- | bad_id | set_it_belongs_to | field2 | field3 | ------------------------------------- | 1 | set1 | qwe | qwe | ------------------------------------- | 2 | set1 | qee | tte | ------------------------------------- | 3 | set1 | q44w | 3qwe | ------------------------------------- | 4 | 234 | qoow | 3qwe | ------------------------------------- Now I have set the first field of every table as the primary key. My question is, how do I connect the field set_of_bads to set_it_belongs_to in the bads table. This way if I want to get the entire set of data that is set1 by calling on the reports table I can do it. Example: hey reports table.. bring up the row that has the report_id 123. Okay thank you.. Now get all the rows from bads that has the set_of_bads value from the row with the report_id 123. Thanks.

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  • Proper way to set class variables

    - by ensnare
    I'm writing a class to insert users into a database, and before I get too far in, I just want to make sure that my OO approach is clean: class User(object): def setName(self,name): #Do sanity checks on name self._name = name def setPassword(self,password): #Check password length > 6 characters #Encrypt to md5 self._password = password def commit(self): #Commit to database >>u = User() >>u.setName('Jason Martinez') >>u.setPassword('linebreak') >>u.commit() Is this the right approach? Should I declare class variables up top? Should I use a _ in front of all the class variables to make them private? Thanks for helping out.

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  • Save data in bulk.

    - by Muhammad Kashif Nadeem
    I have a window having multiple tabs. Each tab having different grids. I want to save all changes on any tab on any grid in bulk. I mean I have one save button which will save all changes in any grid on any tab. I think DataTables will work fine here. Can you suggest me that it is good to use DataTables to ADD/Edit data and save data in bulk using these DataTables OR is there any better way to achieve this. My DAL is generated from LLBLGen Pro (ORM) but you are open to suggest me a solution. Thanks. Edit: I am using Telerik controls so I can get all data in DataTable like DataTable dtProducts = this.radGridView1.DataSource as DataTable;

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  • 7 Card Poker Hand Evaluator

    - by Peter
    Hey, Does anyone know a fast algorithm for evaluating 7 card poker hands? Something which is more efficient than simply brute-force checking a every 21 5-card combination of hands from a set of 7. Cheers, Pete

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  • How to implement an offline reader writer lock

    - by Peter Morris
    Some context for the question All objects in this question are persistent. All requests will be from a Silverlight client talking to an app server via a binary protocol (Hessian) and not WCF. Each user will have a session key (not an ASP.NET session) which will be a string, integer, or GUID (undecided so far). Some objects might take a long time to edit (30 or more minutes) so we have decided to use pessimistic offline locking. Pessimistic because having to reconcile conflicts would be far too annoying for users, offline because the client is not permanently connected to the server. Rather than storing session/object locking information in the object itself I have decided that any aggregate root that may have its instances locked should implement an interface ILockable public interface ILockable { Guid LockID { get; } } This LockID will be the identity of a "Lock" object which holds the information of which session is locking it. Now, if this were simple pessimistic locking I'd be able to achieve this very simply (using an incrementing version number on Lock to identify update conflicts), but what I actually need is ReaderWriter pessimistic offline locking. The reason is that some parts of the application will perform actions that read these complex structures. These include things like Reading a single structure to clone it. Reading multiple structures in order to create a binary file to "publish" the data to an external source. Read locks will be held for a very short period of time, typically less than a second, although in some circumstances they could be held for about 5 seconds at a guess. Write locks will mostly be held for a long time as they are mostly held by humans. There is a high probability of two users trying to edit the same aggregate at the same time, and a high probability of many users needing to temporarily read-lock at the same time too. I'm looking for suggestions as to how I might implement this. One additional point to make is that if I want to place a write lock and there are some read locks, I would like to "queue" the write lock so that no new read locks are placed. If the read locks are removed withing X seconds then the write lock is obtained, if not then the write lock backs off; no new read-locks would be placed while a write lock is queued. So far I have this idea The Lock object will have a version number (int) so I can detect multi-update conflicts, reload, try again. It will have a string[] for read locks A string to hold the session ID that has a write lock A string to hold the queued write lock Possibly a recursion counter to allow the same session to lock multiple times (for both read and write locks), but not sure about this yet. Rules: Can't place a read lock if there is a write lock or queued write lock. Can't place a write lock if there is a write lock or queued write lock. If there are no locks at all then a write lock may be placed. If there are read locks then a write lock will be queued instead of a full write lock placed. (If after X time the read locks are not gone the lock backs off, otherwise it is upgraded). Can't queue a write lock for a session that has a read lock. Can anyone see any problems? Suggest alternatives? Anything? I'd appreciate feedback before deciding on what approach to take.

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  • Building big, immutable objects without using constructors having long parameter lists

    - by Malax
    Hi StackOverflow! I have some big (more than 3 fields) Objects which can and should be immutable. Every time I run into that case i tend to create constructor abominations with long parameter lists. It doesn't feel right, is hard to use and readability suffers. It is even worse if the fields are some sort of collection type like lists. A simple addSibling(S s) would ease the object creation so much but renders the object mutable. What do you guys use in such cases? I'm on Scala and Java, but i think the problem is language agnostic as long as the language is object oriented. Solutions I can think of: "Constructor abominations with long parameter lists" The Builder Pattern Thanks for your input!

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  • How is jQuery so fast?

    - by ClarkeyBoy
    Hey, I have a rather large application which, on the admin frontend, takes a few seconds to load a page because of all the pageviews that it has to load into objects before displaying anything. Its a bit complex to explain how the system works, but a few of my other questions explains the system in great detail. The main difference between what they say and the current system is that the customer frontend no longer loads all the pageviews into objects when a customer first views the page - it simply adds the pageview to the database and creates an object in an unsynchronised list... to put it simply, when a customer views a page it no longer loads all the pageviews into objects; but the admin frontend still does. I have been working on some admin tools on the customer frontend recently, so if an administrator clicks the description of an item in the catalogue then the right hand column will display statistics and available actions for the selected item. To do this the page which gets loaded (through $('action-container').load(bla bla bla);) into the right hand column has to loop through ALL the pageviews - this ultimately means that ALL the pageviews are loaded into objects if they haven't been already. For some reason this loads really REALLY fast. The difference in speed is only like a second on my dev site, but the live site has thousands of pageviews so the difference is quite big... So my question is: why is it that the admin frontend loads so slowly while using $(bla).load(bla); is so fast? I mean whatever method jQuery uses, can't browsers use this method too and load pages super-fast? Obviously not as someone would've done that by now - but I am interested to know just why the difference is so big... is it just my system or is there a major difference in speed between the browser getting a page and jQuery getting a page? Do other people experience the same kind of differences? Thanks in advance, Regards, Richard

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