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• Architecture of interaction modes ("paint tools") for a 3D paint program

  - by Bernhard Kausler

  We are developing a Qt-based application to navigate through and paint on a volume treated as a 3D pixel graphic. The layout of the app consists of three orthogonal slice views on which the user may paint stuff like dots, circles etc. and also erase already painted pixels. Think of a 3D Gimp or MS Paint. How would you design the the architecture for the different interaction modes (i.e. paint tools)? My idea is: use the MVC pattern have a separate controler for every interaction mode install an event filter on all three slice views to collect all incoming user interaction events (mouse, keyboard) redirect the events to the currently active interaction controler I would appreciate critical comments on that idea.

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• Opensource showcase for MVC in Java Swing

  - by Regular John

  I've allready created small desktop CRUD applications using Java/Swing. In hindsight I'm not quite sure if the overall design of these applications is good. I've also done some reading on MVC and looked at different Swing-tutorials. My problem is, that I've got a very theroatical knowledge of MVC and on the other hand, most Swing-resources don't implement the MVC-pattern. Now I would like to get my hands dirty and see how MVC is implemented in Swing in a real-world-application. Are there any opensource project you could recommend? It would be also interesting to have more than one project, to see different approaches. Best fit would be a software, that uses a relational database in the backend, to see an overall design, that I can compare to my former applications.

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• Composite-like pattern and SRP violation

  - by jimmy_keen

  Recently I've noticed myself implementing pattern similar to the one described below. Starting with interface: public interface IUserProvider { User GetUser(UserData data); } GetUser method's pure job is to somehow return user (that would be an operation speaking in composite terms). There might be many implementations of IUserProvider, which all do the same thing - return user basing on input data. It doesn't really matter, as they are only leaves in composite terms and that's fairly simple. Now, my leaves are used by one own them all composite class, which at the moment follows this implementation: public interface IUserProviderComposite : IUserProvider { void RegisterProvider(Predicate<UserData> predicate, IUserProvider provider); } public class UserProviderComposite : IUserProviderComposite { public User GetUser(SomeUserData data) ... public void RegisterProvider(Predicate<UserData> predicate, IUserProvider provider) ... } Idea behind UserProviderComposite is simple. You register providers, and this class acts as a reusable entry-point. When calling GetUser, it will use whatever registered provider matches predicate for requested user data (if that helps, it stores key-value map of predicates and providers internally). Now, what confuses me is whether RegisterProvider method (brings to mind composite's add operation) should be a part of that class. It kind of expands its responsibilities from providing user to also managing providers collection. As far as my understanding goes, this violates Single Responsibility Principle... or am I wrong here? I thought about extracting register part into separate entity and inject it to the composite. As long as it looks decent on paper (in terms of SRP), it feels bit awkward because: I would be essentially injecting Dictionary (or other key-value map) ...or silly wrapper around it, doing nothing more than adding entires This won't be following composite anymore (as add won't be part of composite) What exactly is the presented pattern called? Composite felt natural to compare it with, but I realize it's not exactly the one however nothing else rings any bells. Which approach would you take - stick with SRP or stick with "composite"/pattern? Or is the design here flawed and given the problem this can be done in a better way?

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• Constructs for wrapping a hardware state machine

  - by Henry Gomersall

  I am using a piece of hardware with a well defined C API. The hardware is stateful, with the relevant API calls needing to be in the correct order for the hardware to work properly. The API calls themselves will always return, passing back a flag that advises whether the call was successful, or if not, why not. The hardware will not be left in some ill defined state. In effect, the API calls advise indirectly of the current state of the hardware if the state is not correct to perform a given operation. It seems to be a pretty common hardware API style. My question is this: Is there a well established design pattern for wrapping such a hardware state machine in a high level language, such that consistency is maintained? My development is in Python. I ideally wish the hardware state machine to be abstracted to a much simpler state machine and wrapped in an object that represents the hardware. I'm not sure what should happen if an attempt is made to create multiple objects representing the same piece of hardware. I apologies for the slight vagueness, I'm not very knowledgeable in this area and so am fishing for assistance of the description as well!

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• Best approach for utility class library using Visual Studio

  - by gregsdennis

  I have a collection of classes that I commonly (but not always) use when developing WPF applications. The trouble I have is that if I want to use only a subset of the classes, I have three options: Distribute the entire DLL. While this approach makes code maintenance easier, it does require distributing a large DLL for minimal code functionality. Copy the classes I need to the current application. This approach solves the problem of not distributing unused code, but completely eliminates code maintenance. Maintain each class/feature in a separate project. This solves both problems from above, but then I have dramatically increased the number of files that need to be distributed, and it bloats my VS solution with tiny projects. Ideally, I'd like a combination of 1 & 3: A single project that contains all of my utility classes but builds to a DLL containing only the classes that are used in the current application. Are there any other common approaches that I haven't considered? Is there any way to do what I want? Thank you.

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• Class Design and Structure Online Web Store

  - by Phorce

  I hope I have asked this in the right forum. Basically, we're designing an Online Store and I am designing the class structure for ordering a product and want some clarification on what I have so far: So a customer comes, selects their product, chooses the quantity and selects 'Purchase' (I am using the Facade Pattern - So subsystems execute when this action is performed). My class structure: < Order > < Product > <Customer > There is no inheritance, more Association < Order has < Product , < Customer has < Order . Does this structure look ok? I've noticed that I don't handle the "Quantity" separately, I was just going to add this into the "Product" class, but, do you think it should be a class of it's own? Hope someone can help.

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• Design Pattern for Complex Data Modeling

  - by Aaron Hayman

  I'm developing a program that has a SQL database as a backing store. As a very broad description, the program itself allows a user to generate records in any number of user-defined tables and make connections between them. As for specs: Any record generated must be able to be connected to any other record in any other user table (excluding itself...the record, not the table). These "connections" are directional, and the list of connections a record has is user ordered. Moreover, a record must "know" of connections made from it to others as well as connections made to it from others. The connections are kind of the point of this program, so there is a strong possibility that the number of connections made is very high, especially if the user is using the software as intended. A record's field can also include aggregate information from it's connections (like obtaining average, sum, etc) that must be updated on change from another record it's connected to. To conserve memory, only relevant information must be loaded at any one time (can't load the entire database in memory at load and go from there). I cannot assume the backing store is local. Right now it is, but eventually this program will include syncing to a remote db. Neither the user tables, connections or records are known at design time as they are user generated. I've spent a lot of time trying to figure out how to design the backing store and the object model to best fit these specs. In my first design attempt on this, I had one object managing all a table's records and connections. I attempted this first because it kept the memory footprint smaller (records and connections were simple dicts), but maintaining aggregate and link information between tables became....onerous (ie...a huge spaghettified mess). Tracing dependencies using this method almost became impossible. Instead, I've settled on a distributed graph model where each record and connection is 'aware' of what's around it by managing it own data and connections to other records. Doing this increases my memory footprint but also let me create a faulting system so connections/records aren't loaded into memory until they're needed. It's also much easier to code: trace dependencies, eliminate cycling recursive updates, etc. My biggest problem is storing/loading the connections. I'm not happy with any of my current solutions/ideas so I wanted to ask and see if anybody else has any ideas of how this should be structured. Connections are fairly simple. They contain: fromRecordID, fromTableID, fromRecordOrder, toRecordID, toTableID, toRecordOrder. Here's what I've come up with so far: Store all the connections in one big table. If I do this, either I load all connections at once (one big db call) or make a call every time a user table is loaded. The big issue here: the size of the connections table has the potential to be huge, and I'm afraid it would slow things down. Store in separate tables all the outgoing connections for each user table. This is probably the worst idea I've had. Now my connections are 'spread out' over multiple tables (one for each user table), which means I have to make a separate DB called to each table (or make a huge join) just to find all the incoming connections for a particular user table. I've avoided making "one big ass table", but I'm not sure the cost is worth it. Store in separate tables all outgoing AND incoming connections for each user table (using a flag to distinguish between incoming vs outgoing). This is the idea I'm leaning towards, but it will essentially double the total DB storage for all the connections (as each connection will be stored in two tables). It also means I have to make sure connection information is kept in sync in both places. This is obviously not ideal but it does mean that when I load a user table, I only need to load one 'connection' table and have all the information I need. This also presents a separate problem, that of connection object creation. Since each user table has a list of all connections, there are two opportunities for a connection object to be made. However, connections objects (designed to facilitate communication between records) should only be created once. This means I'll have to devise a common caching/factory object to make sure only one connection object is made per connection. Does anybody have any ideas of a better way to do this? Once I've committed to a particular design pattern I'm pretty much stuck with it, so I want to make sure I've come up with the best one possible.

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• Is there a design pattern for chained observers?

  - by sharakan

  Several times, I've found myself in a situation where I want to add functionality to an existing Observer-Observable relationship. For example, let's say I have an Observable class called PriceFeed, instances of which are created by a variety of PriceSources. Observers on this are notified whenever the underlying PriceSource updates the PriceFeed with a new price. Now I want to add a feature that allows a (temporary) override to be set on the PriceFeed. The PriceSource should still update prices on the PriceFeed, but for as long as the override is set, whenever a consumer asks PriceFeed for it's current value, it should get the override. The way I did this was to introduce a new OverrideablePriceFeed that is itself both an Observer and an Observable, and that decorates the actual PriceFeed. It's implementation of .getPrice() is straight from Chain of Responsibility, but how about the handling of Observable events? When an override is set or cleared, it should issue it's own event to Observers, as well as forwarding events from the underlying PriceFeed. I think of this as some kind of a chained observer, and was curious if there's a more definitive description of a similar pattern.

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• One method with many behaviours or many methods

  - by Krowar

  This question is quite general and not related to a specific language, but more to coding best practices. Recently, I've been developing a feature for my app that is requested in many cases with slightly different behaviours. This function send emails , but to different receivers, or with different texts according to the parameters. The method signature is something like public static sendMail (t_message message = null , t_user receiver = null , stream attachedPiece = null) And then there are many condition inside the method, like if(attachedPiece != null) { } I've made the choice to do it this way (with a single method) because it prevents me to rewrite the (nearly) same method 10 times, but I'm not sure that it's a good practice. What should I have done? Write 10 sendMail method with different parameters? Are there obvious pros and cons for these different ways of programming? Thanks a lot.

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• How to avoid big and clumsy UITableViewController on iOS?

  - by Johan Karlsson

  I have a problem when implementing the MVC-pattern on iOS. I have searched the Internet but seems not to find any nice solution to this problem. Many UITableViewController implementations seems to be rather big. Most examples I have seen lets the UITableViewController implement <UITableViewDelegate> and <UITableViewDataSource>. These implementations are a big reason why UITableViewControlleris getting big. One solution would be to create separate classes that implements <UITableViewDelegate> and <UITableViewDataSource>. Of course these classes would have to have a reference to the UITableViewController. Are there any drawbacks using this solution? In general I think you should delegate the functionality to other "Helper" classes or similar, using the delegate pattern. Are there any well established ways of solving this problem? I do not want the model to contain too much functionality, nor the view. I believe that the logic should really be in the controller class, since this is one of the cornerstones of the MVC-pattern. But the big question is: How should you divide the controller of a MVC-implementation into smaller manageable pieces? (Applies to MVC in iOS in this case) There might be a general pattern for solving this, although I am specifically looking for a solution for iOS. Please give an example of a good pattern for solving this issue. Please provide an argument why your solution is awesome.

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• Design pattern for an ASP.NET project using Entity Framework

  - by MPelletier

  I'm building a website in ASP.NET (Web Forms) on top of an engine with business rules (which basically resides in a separate DLL), connected to a database mapped with Entity Framework (in a 3rd, separate project). I designed the Engine first, which has an Entity Framework context, and then went on to work on the website, which presents various reports. I believe I made a terrible design mistake in that the website has its own context (which sounded normal at first). I present this mockup of the engine and a report page's code behind: Engine (in separate DLL): public Engine { DatabaseEntities _engineContext; public Engine() { // Connection string and procedure managed in DB layer _engineContext = DatabaseEntities.Connect(); } public ChangeSomeEntity(SomeEntity someEntity, int newValue) { //Suppose there's some validation too, non trivial stuff SomeEntity.Value = newValue; _engineContext.SaveChanges(); } } And report: public partial class MyReport : Page { Engine _engine; DatabaseEntities _webpageContext; public MyReport() { _engine = new Engine(); _databaseContext = DatabaseEntities.Connect(); } public void ChangeSomeEntityButton_Clicked(object sender, EventArgs e) { SomeEntity someEntity; //Wrong way: //Get the entity from the webpage context someEntity = _webpageContext.SomeEntities.Single(s => s.Id == SomeEntityId); //Send the entity from _webpageContext to the engine _engine.ChangeSomeEntity(someEntity, SomeEntityNewValue); // <- oops, conflict of context //Right(?) way: //Get the entity from the engine context someEntity = _engine.GetSomeEntity(SomeEntityId); //undefined above //Send the entity from the engine's context to the engine _engine.ChangeSomeEntity(someEntity, SomeEntityNewValue); // <- oops, conflict of context } } Because the webpage has its own context, giving the Engine an entity from a different context will cause an error. I happen to know not to do that, to only give the Engine entities from its own context. But this is a very error-prone design. I see the error of my ways now. I just don't know the right path. I'm considering: Creating the connection in the Engine and passing it off to the webpage. Always instantiate an Engine, make its context accessible from a property, sharing it. Possible problems: other conflicts? Slow? Concurrency issues if I want to expand to AJAX? Creating the connection from the webpage and passing it off to the Engine (I believe that's dependency injection?) Only talking through ID's. Creates redundancy, not always practical, sounds archaic. But at the same time, I already recuperate stuff from the page as ID's that I need to fetch anyways. What would be best compromise here for safety, ease-of-use and understanding, stability, and speed?

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• How can one manage thousands of IF...THEN...ELSE rules?

  - by David

  I am considering building an application, which, at its core, would consist of thousands of if...then...else statements. The purpose of the application is to be able to predict how cows move around in any landscape. They are affected by things like the sun, wind, food source, sudden events etc. How can such an application be managed? I imagine that after a few hundred IF-statements, it would be as good as unpredictable how the program would react and debugging what lead to a certain reaction would mean that one would have to traverse the whole IF-statement tree every time. I have read a bit about rules engines, but I do not see how they would get around this complexity.

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• Understanding Visitor Pattern

  - by Nezreli

  I have a hierarchy of classes that represents GUI controls. Something like this: Control-ContainerControl-Form I have to implement a series of algoritms that work with objects doing various stuff and I'm thinking that Visitor pattern would be the cleanest solution. Let take for example an algorithm which creates a Xml representaion of a hierarchy of objects. Using 'classic' approach I would do this: public abstract class Control { public virtual XmlElement ToXML(XmlDocument document) { XmlElement xml = document.CreateElement(this.GetType().Name); // Create element, fill it with attributes declared with control return xml; } } public abstract class ContainerControl : Control { public override XmlElement ToXML(XmlDocument document) { XmlElement xml = base.ToXML(document); // Use forech to fill XmlElement with child XmlElements return xml; } } public class Form : ContainerControl { public override XmlElement ToXML(XmlDocument document) { XmlElement xml = base.ToXML(document); // Fill remaining elements declared in Form class return xml; } } But I'm not sure how to do this with visitor pattern. This is the basic implementation: public class ToXmlVisitor : IVisitor { public void Visit(Form form) { } } Since even the abstract classes help with implementation I'm not sure how to do that properly in ToXmlVisitor. Perhaps there is a better solution to this problem. The reason that I'm considering Visitor pattern is that some algorithms will need references not available in project where the classes are implemented and there is a number of different algorithms so I'm avoiding large classes. Any thoughts are welcome.

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• Effective template system

  - by Alex

  I'm building a content management system, and need advice on which theming structure should I adopt. A few options (This is not a complete list): Wordpress style: the controller decides what template to load based on the user request, like: home page / article archive / single article page etc. each of these templates are unrelated to other templates, and must exist within the theme the theme developer decides if (s)he want to use inner-templates (like "sidebar", "sidebar item"), and includes them manually where (s)he thinks are needed. Drupal style: the controller gives control to the theme developer only to inner-templates; if they don't exist it falls back internally to some default templates (I find this very restrictive) Funky style: the controller only loads a "index.php" template and provides the theme developer conditional tags, which he can use to include inner-templates if (s)he wants. Among these styles, or others what style of template system allows for fast development and a more concise design and implementation.

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• Advantages of Singleton Class over Static Class?

  Point 1) Singleton We can get the object of singleton and then pass to other methods. Static Class We can not pass static class to other methods as we pass objects Point 2) Singleton In future, it is easy to change the logic of of creating objects to some pooling mechanism. Static Class Very difficult to implement some pooling logic in case of static class. We would need to make that class as non-static and then make all the methods non-static methods, So entire your code needs to be changed. Point3:) Singleton Can Singletone class be inherited to subclass? Singleton class does not say any restriction of Inheritence. So we should be able to do this as long as subclass is also inheritence.There's nothing fundamentally wrong with subclassing a class that is intended to be a singleton. There are many reasons you might want to do it. and there are many ways to accomplish it. It depends on language you use. Static Class We can not inherit Static class to another Static class in C#. Think about it this way: you access static members via type name, like this: MyStaticType.MyStaticMember(); Were you to inherit from that class, you would have to access it via the new type name: MyNewType.MyStaticMember(); Thus, the new item bears no relationships to the original when used in code. There would be no way to take advantage of any inheritance relationship for things like polymorphism. span.fullpost {display:none;}

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• Optimization ended up in casting an object at each method call

  - by Aybe

  I've been doing some optimization for the following piece of code : public void DrawLine(int x1, int y1, int x2, int y2, int color) { _bitmap.DrawLineBresenham(x1, y1, x2, y2, color); } After profiling it about 70% of the time spent was in getting a context for drawing and disposing it. I ended up sketching the following overload : public void DrawLine(int x1, int y1, int x2, int y2, int color, BitmapContext bitmapContext) { _bitmap.DrawLineBresenham(x1, y1, x2, y2, color, bitmapContext); } Until here no problems, all the user has to do is to pass a context and performance is really great as a context is created/disposed one time only (previously it was a thousand times per second). The next step was to make it generic in the sense it doesn't depend on a particular framework for rendering (besides .NET obvisouly). So I wrote this method : public void DrawLine(int x1, int y1, int x2, int y2, int color, IDisposable bitmapContext) { _bitmap.DrawLineBresenham(x1, y1, x2, y2, color, (BitmapContext)bitmapContext); } Now every time a line is drawn the generic context is casted, this was unexpected for me. Are there any approaches for fixing this design issue ? Note : _bitmap is a WriteableBitmap from WPF BitmapContext is from WriteableBitmapEx library DrawLineBresenham is an extension method from WriteableBitmapEx

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• Help me classify this type of software architecture

  - by Alex Burtsev

  I read some books about software architecture as we are using it in our project but I can't classify the architecture properly. It's some kind of Enterprise Architecture, but what exactly... SOA, ESB (Enterprise Service Bus), Message Bus, Event Driven SOA, there are so many terms in Enterprise software.... The system is based on custom XML messages exchanges between services. (it's not SOAP, nor any other XML based standard, just plain XML). These messages represent notifications (state changes) that are applied to the Domain model, (it's not like CRUD when you serialize the whole domain object, and pass it to service for persistence). The system is centralized, and system participants use different programming languages and frameworks (c++, c#, java). Also, messages are not processed at the moment they are received as they are stored first and the treatment begins on demand. It's called SOA+EDA -:)

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• What are the advantages of the delegate pattern over the observer pattern?

  - by JoJo

  In the delegate pattern, only one object can directly listen to another object's events. In the observer pattern, any number of objects can listen to a particular object's events. When designing a class that needs to notify other object(s) of events, why would you ever use the delegate pattern over the observer pattern? I see the observer pattern as more flexible. You may only have one observer now, but a future design may require multiple observers.

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• Use adapter pattern for coupled classes

  - by kaiseroskilo

  I need (for unit testing purposes) to create adapters for external library classes.ExchangeService and ContactsFolder are Microsoft's implementations in its' EWS library. So I created my adapters that implement my interfaces, but it seems that contactsFolder has a dependency for ExchangeService in its' constructor. The problem is that I cannot instantiate ContactsFolderAdapter without somehow accessing the actual ExchangeService instance (I see only ExchangeServiceAdapter in scope). Is there a better pattern for this that retains the adapter classes? Or should I "infect" ExchangeServiceAdapter with some kind of GetActualObject method?

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• Explanation of the definition of interface inheritance as described in GoF book

  - by Geek

  I am reading the first chapter of the Gof book. Section 1.6 discusses about class vs interface inheritance: Class versus Interface Inheritance It's important to understand the difference between an object's class and its type. An object's class defines how the object is implemented.The class defines the object's internal state and the implementation of its operations.In contrast,an object's type only refers to its interface--the set of requests on which it can respond. An object can have many types, and objects of different classes can have the same type. Of course, there's a close relationship between class and type. Because a class defines the operations an object can perform, it also defines the object's type . When we say that an object is an instance of a class, we imply that the object supports the interface defined by the class. Languages like c++ and Eiffel use classes to specify both an object's type and its implementation. Smalltalk programs do not declare the types of variables; consequently,the compiler does not check that the types of objects assigned to a variable are subtypes of the variable's type. Sending a message requires checking that the class of the receiver implements the message, but it doesn't require checking that the receiver is an instance of a particular class. It's also important to understand the difference between class inheritance and interface inheritance (or subtyping). Class inheritance defines an object's implementation in terms of another object's implementation. In short, it's a mechanism for code and representation sharing. In contrast,interface inheritance(or subtyping) describes when an object can be used in place of another. I am familiar with the Java and JavaScript programming language and not really familiar with either C++ or Smalltalk or Eiffel as mentioned here. So I am trying to map the concepts discussed here to Java's way of doing classes, inheritance and interfaces. This is how I think of of these concepts in Java: In Java a class is always a blueprint for the objects it produces and what interface(as in "set of all possible requests that the object can respond to") an object of that class possess is defined during compilation stage only because the class of the object would have implemented those interfaces. The requests that an object of that class can respond to is the set of all the methods that are in the class(including those implemented for the interfaces that this class implements). My specific questions are: Am I right in saying that Java's way is more similar to C++ as described in the third paragraph. I do not understand what is meant by interface inheritance in the last paragraph. In Java interface inheritance is one interface extending from another interface. But I think the word interface has some other overloaded meaning here. Can some one provide an example in Java of what is meant by interface inheritance here so that I understand it better?

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• Approach on Software Development Architecture

  - by john ryan

  Hi i am planning to standardize our way of creating project for our new projects. Currently we are using 3tier architecture where we have our ClassLibrary Project where it includes our Data Access Layer and Business Layer Something like: Solution ClassLibrary >ClassLibrary Project : >DAL(folder) > DAL Classes >BAL(folder) > BAL Classes And this Class Library dll was reference on our presentation Layer Project which are the Application(web/desktop) Something like: Solution WebUniversitySystem >Libraries(folder) > ClassLibrary.dll >WebUniversitySystem(Project): >Reference ClassLibrary.dll >Pages etc... Now i am planning to do is something like: Solution WebUniversitySystem >DataAccess(Project) >BusinesLayer(Project) >Reference DAL >WebUniversitySystem(Project): >Reference BAL >Pages etc... Is this Ok ? Or there is a good Approach that we can follow? Thanks In Regards

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• When does 'optimizing code' == 'structuring data'?

  - by NewAlexandria

  A recent article by ycombinator lists a comment with principles of a great programmer. #7. Good programmer: I optimize code. Better programmer: I structure data. Best programmer: What's the difference? Acknowledging subjective and contentious concepts - does anyone have a position on what this means? I do, but I'd like to edit this question later with my thoughts so-as not to predispose the answers.

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• Subclassing to avoid line length

  - by Super User

  The standard line length of code is 80 characters per line. This is accepted and followed by the most of programmers. I working on a state machine of a character and is necessary for me follow this too. I have four classes who pass this limit. I can subclass each class in two more and then avoid the line length limit. class Stand class Walk class Punch class Crouch The new classes would be StandLeft, StandRight and so on. Stand, Walk, Punch and Crouch would be then abstract classes. The question if there is a limit for the long of the hierarchies tree or this is depends of the case.

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• how to improve design ability

  - by Cong Hui

  I recently went on a couple of interviews and all of them asked a one or two design questions, like how you would design a chess, monopoly, and so on. I didn't do good on those since I am a college student and lack of the experience of implementing big and complex systems. I figure the only way to improve my design capability is to read lots of others' code and try to implement myself. Therefore, for those companies that ask these questions, what are their real goals in this? I figure most of college grads start off working in a team guided by a senior leader in their first jobs. They might not have lots of design experience fresh out of colleges. Anyone could give pointers about how to practice those skills? Thank you very much

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• MVP Pattern Philsophical Question - Security Checking in UI

  - by Brian

  Hello, I have a philosophical question about the MVP pattern: I have a component that checks whether a user has access to a certain privilege. This privilege turns on or off certain UI features. For instance, suppose you have a UI grid, and for each row that gets bound, I do a security check to see if certain features in the grid should be enabled or disabled. There are two ways to do this: have the UI/view call the component's method, determine if it has access, and enable/disable or show/hide. The other is have the view fire an event to the presenter, have the presenter do the check and return the access back down to the view through the model or through the event arg. As per the MVP pattern, which component should security checks fit into, the presenter or the view? Since the view is using it to determine its accessibility, it seems more fitting in the view, but it is doing database checks and all inside this business component, and there is business logic there, so I can see the reverse argument too. Thoughts? Thanks.

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