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  • MVVM application architecture, where to put dependency injection configuration class, BusinessLayer and Common interfaces?

    - by gt.guybrush
    Planning my architecture for an MVVM application I come to this: MyApp.UI View MyApp.BusinessLayer ViewModel MyApp.DataAccessLayer RepositoryImplEF MyApp.DomainLayer DomainObject RepositoryInterface MyApp.Common Logging Security Utility (contains some reflection method used by many levels) CustomException MyApp.UnitTest I was inspired by Domain-driven-desing, test-driven-development and onion architecture but not sure to have done all well. I am not sure of a couple of things: where to put dependency injection configuration class? In the common project? where to put BusinessLayer interfaces? in Domain layer? where to put Common interfaces? in Domain layer? But Common in referenced from domain (for some reflection utilities and for DI if the response to 1. is yes) and circular reference isn't good

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  • Law of Demeter in MVC regarding Controller-View communication

    - by Antonio MG
    The scenario: Having a Controller that controls a view composed of complex subviews. Each one of those subviews is a separated class in a separate file. For example, one of those subviews is called ButtonsView, and has a bunch of buttons. The Controller has to access those buttons. Would accessing those buttons like this: controllerMainView.buttonsView.firstButton.state(); be a violation of the LOD? On one hand, it could be yes because the controller is accessing the inner hierarchy of the view. On the other, a Controller should be aware of what happens inside the view and how is composed. Any thoughts?

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  • What kind of graphics would you like better? [ pictures ] [closed]

    - by Roger Travis
    I am looking forward to make an android game, something angrybirds style. I've already made my own engine and now have to decide what kind of graphics should I make. It could be either realistic, like that or a doodle-style like this Right now the first one looks more appealing to me... on the other hand, doodle-graphics are very easy to draw and their transparency doesn't seem to slow down the engine much. What do you think?

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  • Implementing Command Pattern in Web Application

    - by KingOfHypocrites
    I'm looking to implement the command pattern in a web application (asp.net c#)... Since the commands come in text format from the client, what is the best way to translate the string to a command object? Should I use reflection? Currently I just assume the command that comes in matches the file name of a user control. This is a bit of a hack. Rather than have a select case statement that says if string = "Dashboard" then call Dashboard.Execute(), is there a pattern for working with commands that originate as strings?

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  • Storing images in file system and returning URLs or virtually resizing and returning byte arrays?

    - by ismaelf
    I need to create a REST web service to manage user submitted images and displaying them all in a website. There are multiple websites that are going to use this service to manage and display images. The requirements are to have 5 pre-defined image sizes available. The 2 options I see are the following: The web service will create the 5 images, store them in the file system and and store the URL's in the database when the user submits the image. When the image is requested, the web service will return an array of URLs. I see this option to be a little hard on the hard drive. The estimates are 10,000 users per site, and lets say, 100 sites. The heavy processing will be done when the user submits the image and each image is going to be pulled from the File System. The web service will store just the image that the user submits in the file system and it's URL in the database. When the user request images, the web service will get the info from the DB, load the image on memory, create its 5 instances and return an object with 5 image arrays (I will probably cache the arrays). This option is harder on the processor and memory. The heavy processing will be done when the images get requested. A plus I see for option 2 is that it will give me the option to rewrite the URL of the image and make them site dependent (prettier) than having a image repository for all websites. But this is not a big deal. What do you think of these options? Do you have any other suggestions?

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  • How can I designed multi-threaded application for larger user base

    - by rokonoid
    Here's my scenario, I need to develop a scalable application. My user base may be over 100K, every user has 10 or more small tasks. Tasks check every minute with a third party application through web services, retrieving data which is written in the database, then the data is forwarded to it's original destination. So here's the processing of a small task: while(true){ Boolean isNewInformationAvailable = checkWhetherInformationIsAvailableOrNot(); If(isNewInformationAvailable ==true){ fetchTheData(); writeToDatabase(); findTheDestination(); deliverTheData(); isAvailable =false; } } Here is the question: as the application is large, how should I approach designing this. I'm going to use Java to write it. Should I use concurrency, and how would you manage the concurrency?

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  • Too complex/too many objects?

    - by Mike Fairhurst
    I know that this will be a difficult question to answer without context, but hopefully there are at least some good guidelines to share on this. The questions are at the bottom if you want to skip the details. Most are about OOP in general. Begin context. I am a jr dev on a PHP application, and in general the devs I work with consider themselves to use many more OO concepts than most PHP devs. Still, in my research on clean code I have read about so many ways of using OO features to make code flexible, powerful, expressive, testable, etc. that is just plain not in use here. The current strongly OO API that I've proposed is being called too complex, even though it is trivial to implement. The problem I'm solving is that our permission checks are done via a message object (my API, they wanted to use arrays of constants) and the message object does not hold the validation object accountable for checking all provided data. Metaphorically, if your perm containing 'allowable' and 'rare but disallowed' is sent into a validator, the validator may not know to look for 'rare but disallowed', but approve 'allowable', which will actually approve the whole perm check. We have like 11 validators, too many to easily track at such minute detail. So I proposed an AtomicPermission class. To fix the previous example, the perm would instead contain two atomic permissions, one wrapping 'allowable' and the other wrapping 'rare but disallowed'. Where previously the validator would say 'the check is OK because it contains allowable,' now it would instead say '"allowable" is ok', at which point the check ends...and the check fails, because 'rare but disallowed' was not specifically okay-ed. The implementation is just 4 trivial objects, and rewriting a 10 line function into a 15 line function. abstract class PermissionAtom { public function allow(); // maybe deny() as well public function wasAllowed(); } class PermissionField extends PermissionAtom { public function getName(); public function getValue(); } class PermissionIdentifier extends PermissionAtom { public function getIdentifier(); } class PermissionAction extends PermissionAtom { public function getType(); } They say that this is 'not going to get us anything important' and it is 'too complex' and 'will be difficult for new developers to pick up.' I respectfully disagree, and there I end my context to begin the broader questions. So the question is about my OOP, are there any guidelines I should know: is this too complicated/too much OOP? Not that I expect to get more than 'it depends, I'd have to see if...' when is OO abstraction too much? when is OO abstraction too little? how can I determine when I am overthinking a problem vs fixing one? how can I determine when I am adding bad code to a bad project? how can I pitch these APIs? I feel the other devs would just rather say 'its too complicated' than ask 'can you explain it?' whenever I suggest a new class.

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  • What are the advantages of storing xml in a relational database?

    - by Chris
    I was poking around the AdventureWorks database today and I noticed that a number of tables (HumanResources.JobCandidate and Sales.Individual for example) have a column which is storing xml data. What I would to know is, what is the advantage of storing basically a database table row's worth of data in another table's column? Doesn't this make it difficult to query off of this information? Or is the assumption that the data won't need to be queried and just needs to be stored?

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  • Is there a standard for machine-readable descriptions of RESTful services?

    - by ecmendenhall
    I've interacted with a few RESTful APIs that provided excellent documentation for humans and descriptive URIs, but none of them seem to return machine-readable descriptions of themselves. It's not too tough to write methods of my own that assemble the right paths, and many language-specific API libraries are already just wrappers around RESTful requests. But the next level of abstraction seems really useful: a library that could read in an API's own machine readable documentation and generate the wrappers automatically, perhaps with a call to some standard URI like base_url + '/documentation' Are there any standards for machine-readable API documentation? Am I doing REST wrong? I am a relatively new programmer, but this seems like a good idea.

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  • What is a normalized Vector?

    - by draiden
    Can someone explain the following code? I need to learn what each part means so I can turn it into enemy movement in a space shoot-em-up Vec2d playerPos; Vec2d direction; // always normalized float velocity; I get the above is naming two 2d Vector objects, and creating a variable called velocity. I'm not sure what the normalized comment is about, though. update() { direction = normalize(playerPos - enemyPos); playerPos = playerPos + direction * velocity; }

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  • I know of three ways in which SRP helps reduce coupling. Are there even more? [closed]

    - by user1483278
    I'd like to figure all the possible ways SRP helps us reduce coupling. Thus far I can think of three: 1) If class A has more than one responsibility, these responsibilities become coupled and as such changes to one of these responsibilities may require changes to other of A's responsibilities. 2) Related functionality usually needs to be changed for the same reason and by grouping it togerther in a single class, the changes can be made in as few places as possible ( at best changes only need be made to the class which groups together these functionalities) 3) Assuming class A performs two tasks ( thus may change for two reasons ), then number of classes utilising A will be greater than if A performed just a single task ( reason being that some classes will need A to perform first task, other will need A for second task, and still others will utilise it for both tasks ).This also means that when A breaks, the number of classes ( utilising A ) being impaired will be greater than if A performed just a single task. Can SRP also help reduce coupling in any other way, not described above? Thank you

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  • Do functional generics exist or what is the correct name for them if they do?

    - by voroninp
    Consider the following generic class public class EntityChangeInfo<EntityType,TEntityKey> { ChangeTypeEnum ChangeType {get;} TEntityKeyType EntityKey {get;} } Here EntityType unambiguously defines TEntityKeyType. So it would be nice to have some kind of types' map public class EntityChangeInfo<EntityType,TEntityKey> with map < [ EntityType : Person -> TEntityKeyType : int] [ EntityType : Car -> TEntityKeyType : CarIdType ]> { ChangeTypeEnum ChangeType {get;} TEntityKeyType EntityKey {get;} } Another one example is: public class Foo<TIn> with map < [TIn : Person -> TOut1 : string, TOut2 : int, ..., TOutN : double ] [TIn : Car -> TOut1 : int, TOut2 :int, ..., TOutN : Price ] > { TOut1 Prop1 {get;set;} TOut2 Prop2 {get;set;} ... TOutN PropN {get;set;} } The reasonable question how this can be interpreted by the compiler? Well, for me it is just the sortcut for two structurally similar classes: public sealed class Foo<Person> { string Prop1 {get;set;} int Prop2 {get;set;} ... double PropN {get;set;} } public sealed class Foo<Car> { int Prop1 {get;set;} int Prop2 {get;set;} ... Price PropN {get;set;} } But besides this we could imaging some update of the Foo<: public class Foo<TIn> with map < [TIn : Person -> TOut1 : string, TOut2 : int, ..., TOutN : double ] [TIn : Car -> TOut1 : int, TOut2 :int, ..., TOutN : Price ] > { TOut1 Prop1 {get;set;} TOut2 Prop2 {get;set;} ... TOutN PropN {get;set;} public override string ToString() { return string.Format("prop1={0}, prop2={1},...propN={N-1}, Prop1, Prop2,...,PropN); } } This all can seem quite superficial but the idea came when I was designing the messages for our system. The very first class. Many messages with the same structrue should be discriminated by the EntityType. So the question is whether such construct exist in any programming language?

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  • Should single purpose utility app use a class

    - by jmoreno
    When writing a small utility app, that does just one thing, should that one thing be encapsulated in a seperate class, or just let it be part of whatever class/module is used to start the application? I.e. Main would consist of 2 or three lines calling the constructor and then the DoIt methods, nothing else. Or should Main be the DoIt method, with whatever functions it needs added to the main class? Asking because I want to get some alternative perspective, but couldn't find a similar question. If my google-fu is bad and there's a dup, please close.

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  • What is the most concise, unambiguous syntax for operator associated methods (for overloading etc.) that doesn't pollute the namespace?

    - by Doug Treadwell
    Python tends to add double underscores before its built-in or overloadable operator methods, like __add(), whereas C++ requires declaring overloaded operators as operator + (Thing& thing) { /* code */ } for example. Personally I like the operator syntax because it seems to be more explicit and keeps these operator overloading methods separated from other methods without introducing weird prefix notation. What are your thoughts? Also, what about the case of built-in methods that are needed for the programming language to work properly? Is name mangling (like adding __ prefix or sys or something) the best solution here? What do you think about having another type of method declaration, like ... "system method" for lack of creativity at the moment. So there would be two kinds of declarations: int method_name() { ... } system int method_name() { ... } ... and the call would need to be different to distinguish between them. obj.method_name(); vs obj:method_name(); perhaps, assuming a language where : can be unambiguously used in this situation. obj.method_name() vs obj.(system method_name)() Sure, the latter is ugly, but the idea is to make the common case simple and system stuff should be kept out of the way. Maybe the Objective-C notation of method calls? [obj method_name]? Are there more alternatives? Please make suggestions.

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  • Implenting ActiveRecord with inheritance?

    - by King
    I recently converted an old application that was using XML files as the data store to use SQL instead. To avoid a lot of changes I basically created ActiveRecord style classes that inherited from the original business objects. For example SomeClassRecord :SomeClass //ID Property //Save method I then used this new class in place of the other one, because of polymorphism I didn't need to change any methods that took SomeClass as a parameter. Would this be considered 'Bad'? What would be a better alternative?

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  • How is it possible to write the compiler of a programming language with that language itself [closed]

    - by tugberk
    Possible Duplicate: How could the first C++ compiler be written in C++? You probably heard that Microsoft released a new language called TypeScript which is a the typed superset of JavaScript. The most interesting thing that makes me wonder is the fact that its compiler writen in TypeScript itself. Call me ignorant but I really couldn't figure out in my head how that is possible. This is just like chicken and egg problem in my head because there is no compiler to compile TypeScript's compiler in the first place. How is it possible to write a compiler of the compiler of a programming language with that language?

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  • What to do if I hate C++ header files?

    - by BlaXpirit
    I was always confused about header files. They are so strange: you include .h file which doesn't include .cpp but .cpp are somehow compiled too. NOTE: I UNDERSTAND EVERYTHING ABOUT THE HEADERS, PLEASE DON'T TELL ME I'M STUPID OR SHOULD USE OTHER LANGUAGE Recently I joined a team project, and of course, both .h and .cpp are used. I understand that this is very important, but I can't live with copy-pasting every function declaration in each of multiple classes we have. How do I handle the 2-file convention efficiently? Are there any tools to help with that, or automatically change one file that looks like example below to .h and .cpp? (specifically for MS VC++ 2010) class A { ... Type f(Type a,Type b) { //implementation here, not in another file! } ... }; Type f(Type a) { //implementation here } ...

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  • Player rewards in games where you normally have nothing to purchase

    - by PeterK
    In many games there are rewards such as gold coins, points, etc. When these rewards can be used to purchase in-game items, it motivates the player to keep playing. Let's say we have an online game, poker, Yatzy etc. What type of reward would keep the players playing if there are few in-game items available to buy, or none at all? What I am looking for is a reward system that entices the players to play more in a game environment where there isn't that much to purchase. For example, there isn't much to buy in a poker or Yatzy game with the gold you win. I guess having some titles that are added to the userid is one way, or maybe purchasing a logo for the id... A leaderboard is another. Any thoughts on this?

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  • Does an inventory limit in an MMORPG make sense?

    - by Philipp
    I am currently developing a simple 2d MMORPG. My current focus is the inventory system. I am currently wondering if I should implement a limit on what a player character can carry. Either in form of a maximum weight, a limited number of inventory slots, or a combination of both. Almost every MMORPG I ever played limits inventory space. But plausibility aside, is this really necessary from a gameplay point of view? Maybe it would in fact improve the game experience when I just let the players carry as much stuff as they want. tl;dr: What is the game development rationale behind limiting carrying capacity of player characters?

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  • Set modified date = created date or null on record creation?

    - by User
    I've been following the convention of adding created and modified columns to most of my database tables. I also have been leaving the modified column as null on record creation and only setting a value on actual modification. The other alternative is to set the modified date to be equal to created date on record creation. I've been doing it the former way but I recent ran into one con which is seriously making me think of switching. I needed to set a database cache dependency to find out if any existing data has been changed or new data added. Instead of being able to do the following: SELECT MAX(modified) FROM customer I have to do this: SELECT GREATEST(MAX(created), MAX(modified)) FROM customer The negative being that it's a more complicated query and slower. Another thing is in file systems I believe they usually use the second convention of setting modified date = created date on creation. What are the pros and cons of the different methods? That is, what are the issues to consider?

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  • Are null references really a bad thing?

    - by Tim Goodman
    I've heard it said that the inclusion of null references in programming languages is the "billion dollar mistake". But why? Sure, they can cause NullReferenceExceptions, but so what? Any element of the language can be a source of errors if used improperly. And what's the alternative? I suppose instead of saying this: Customer c = Customer.GetByLastName("Goodman"); // returns null if not found if (c != null) { Console.WriteLine(c.FirstName + " " + c.LastName + " is awesome!"); } else { Console.WriteLine("There was no customer named Goodman. How lame!"); } You could say this: if (Customer.ExistsWithLastName("Goodman")) { Customer c = Customer.GetByLastName("Goodman") // throws error if not found Console.WriteLine(c.FirstName + " " + c.LastName + " is awesome!"); } else { Console.WriteLine("There was no customer named Goodman. How lame!"); } But how is that better? Either way, if you forget to check that the customer exists, you get an exception. I suppose that a CustomerNotFoundException is a bit easier to debug than a NullReferenceException by virtue of being more descriptive. Is that all there is to it?

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  • Using Copyrighted Images

    - by TMP
    I was thinking about developing a sidescrolling platformer very similar to an old Mario and Luigi game for NES. To start out I was thinking about taking the images from a site like this: http://www.mariouniverse.com/sprites/nes/smb3 Which clearly states a copyright. I was wondering how far I am allowed to take these images. I figure I'm probably allowed to use it for personal development, but what if I publish the game as an exe file and send it to some friends? I figured a definite no-no would be selling the game with the copyrighted images included. A secondary question would be whether or not I would be allowed to modify them slightly and then call them my own.

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  • Identifying which pattern fits better.

    - by Daniel Grillo
    I'm developing a software to program a device. I have some commands like Reset, Read_Version, Read_memory, Write_memory, Erase_memory. Reset and Read_Version are fixed. They don't need parameters. Read_memory and Erase_memory need the same parameters that are Length and Address. Write_memory needs Lenght, Address and Data. For each command, I have the same steps in sequence, that are something like this sendCommand, waitForResponse, treatResponse. I'm having difficulty to identify which pattern should I use. Factory, Template Method, Strategy or other pattern. Edit I'll try to explain better taking in count the given comments and answers. I've already done this software and now I'm trying to refactoring it. I'm trying to use patterns, even if it is not necessary because I'm taking advantage of this little software to learn about some patterns. Despite I think that one (or more) pattern fits here and it could improve my code. When I want to read version of the software of my device, I don't have to assembly the command with parameters. It is fixed. So I have to send it. After wait for response. If there is a response, treat (or parse) it and returns. To read a portion of the memory (maximum of 256 bytes), I have to assembly the command using the parameters Len and Address. So I have to send it. After wait for response. If there is a response, treat (or parse) it and returns. To write a portion in the memory (maximum of 256 bytes), I have to assembly the command using the parameters Len, Address and Data. So I have to send it. After wait for response. If there is a response, treat (or parse) it and returns. I think that I could use Template Method because I have almost the same algorithm for all. But the problem is some commands are fixes, others have 2 or 3 parameters. I think that parameters should be passed on the constructor of the class. But each class will have a constructor overriding the abstract class constructor. Is this a problem for the template method? Should I use other pattern?

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  • Should I make up my own HTTP status codes? (a la Twitter 420: Enhance Your Calm)

    - by Max Bucknell
    I'm currently implementing an HTTP API, my first ever. I've been spending a lot of time looking at the Wikipedia page for HTTP status codes, because I'm determined to implement the right codes for the right situations. Listed on that page is a code with number 420, which is a custom code that Twitter used to use for rate limiting. There is already a code for rate limiting, though. It's 429. This led me to wonder why they would set a custom one, when there is already a use case. Is that just being cute? And if so, then which circumstances would make it acceptable to return a different status code, and what, if any problems may clients have with it? I read somewhere that Mozilla doesn't implement the joke 418: I’m a teapot response, which makes me think that clients choose which status codes they implement. If that's true, then I can imagine Twitter's funny little enhance your calm code being problematic. Unless I'm mistaken, and we can appropriate any code number to mean whatever we like, and that only convention dictates that 404 means not found, and 429 means take it easy.

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  • Should I always encapsulate an internal data structure entirely?

    - by Prog
    Please consider this class: class ClassA{ private Thing[] things; // stores data // stuff omitted public Thing[] getThings(){ return things; } } This class exposes the array it uses to store data, to any client code interested. I did this in an app I'm working on. I had a ChordProgression class that stores a sequence of Chords (and does some other things). It had a Chord[] getChords() method that returned the array of chords. When the data structure had to change (from an array to an ArrayList), all client code broke. This made me think - maybe the following approach is better: class ClassA{ private Thing[] things; // stores data // stuff omitted public Thing[] getThing(int index){ return things[index]; } public int getDataSize(){ return things.length; } public void setThing(int index, Thing thing){ things[index] = thing; } } Instead of exposing the data structure itself, all of the operations offered by the data structure are now offered directly by the class enclosing it, using public methods that delegate to the data structure. When the data structure changes, only these methods have to change - but after they do, all client code still works. Note that collections more complex than arrays might require the enclosing class to implement even more than three methods just to access the internal data structure. Is this approach common? What do you think of this? What downsides does it have other? Is it reasonable to have the enclosing class implement at least three public methods just to delegate to the inner data structure?

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