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• design using a readonly class in c#

  - by edosoft

  Hi Small design question here. I'm trying to develop a calculation app in C#. I have a class, let's call it InputRecord, which holds 100s of fields (multi dimensional arrays) This InputRecordclass will be used in a number of CalculationEngines. Each CalculcationEngine can make changes to a number of fields in the InputRecord. These changes are steps needed for it's calculation. Now I don't want the local changes made to the InputRecord to be used in other CalculcationEngine's classes. The first solution that comes to mind is using a struct: these are value types. However I'd like to use inheritance: each CalculationEngine needs a few fields only relevant to that engine: it's has it's own InputRecord, based on BaseInputRecord. Can anyone point me to a design that will help me accomplish this?

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• multiple classes with same methods - best pattern

  - by Tony

  I have a few classes in my current project where validation of Email/Website addresses is necessary. The methods to do that are all the same. I wondered what's the best way to implement this, so I don't need to have these methods copy pasted everywhere? The classes themselves are not necessarily related, they only have those validation methods in common.

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• P/Invoke or C++/CLI for wrapping a C library

  - by Ian G

  Have a moderate size (40-odd function) C API that needs to be called from a C# project. The functions logically break up to form a few classes that will be API presented to the rest of the project. Are there any objective reasons to prefer P/Invoke or C++/CLI for the interoperability underneath that API, in terms of robustness, maintainability, deployment, ...? The issues I could think of that might be, but aren't problematic are: C++/CLI will require an separate assembly, the P/Invoke classes can be in the main assembly. (We've already got multiple assemblies and there'll be the C dlls anyway so not a major issue). Performance doesn't seem differ noticeable between the two methods. Issues that I'm not sure about are: My feeling is C++/CLI will be easier to debug if there's inter-op problem, is this true? Language familiarity enough people know C# and C++ but knowledge of details of C++/CLI are rarer here. Anything else?

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• Facade controller, is it efficient?

  - by Berlioz

  Using a facade controller pattern in .net. It seems as if though it is not efficient BECAUSE, for every event that happens in a domain object(Sales, Register, Schedule, Car) it has to be subscribed to by the controller(use case controller) and then the controller in turn has to duplicate that same event to make it available for the presentation, so that the presentation can show it to the user. Does this make sense? Please comment!

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• One executable with cmd-line params or just many satellite executables?

  - by Nikos Baxevanis

  I design an application back-end. For now, it is a .NET process (a Console Application) which hosts various communication frameworks such as Agatha and NServiceBus. I need to periodically update my datastore with values (coming from the application while it's running). I found three possible ways: Accept command line arguments, so I can call my console app with -update. On start up a background thread will periodically invoke the update method. Create an updater.exe app which will do the updates, but I will have code duplication since in some way it will need to query the data from the source in order to save it to the datastore. Which one is better?

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• A better way to delete a list of elements from multiple tables

  - by manyxcxi

  I know this looks like a 'please write the code' request, but some basic pointer/principles for doing this the right way should be enough to get me going. I have the following stored procedure: CREATE PROCEDURE `TAA`.`runClean` (IN idlist varchar(1000)) BEGIN DECLARE EXIT HANDLER FOR NOT FOUND ROLLBACK; DECLARE EXIT HANDLER FOR SQLEXCEPTION ROLLBACK; DECLARE EXIT HANDLER FOR SQLWARNING ROLLBACK; START TRANSACTION; DELETE FROM RunningReports WHERE run_id IN (idlist); DELETE FROM TMD_INDATA_INVOICE WHERE run_id IN (idlist); DELETE FROM TMD_INDATA_LINE WHERE run_id IN (idlist); DELETE FROM TMD_OUTDATA_INVOICE WHERE run_id IN (idlist); DELETE FROM TMD_OUTDATA_LINE WHERE run_id IN (idlist); DELETE FROM TMD_TEST WHERE run_id IN (idlist); DELETE FROM RunHistory WHERE id IN (idlist); COMMIT; END $$ It is called by a PHP script to clean out old run history. It is not particularly efficient as you can see and I would like to speed it up. The PHP script gathers the ids to remove from the tables with the following query: $query = "SELECT id, stop_time FROM RunHistory WHERE config_id = $configId AND save = 0 AND NOT(stop_time IS NULL) ORDER BY stop_time"; It keeps the last five run entries and deletes all the rest. So using this query to bring back all the IDs, it determines which ones to delete and keeps the 'newest' five. After gathering the IDs it sends them to the stored procedure to remove them from the associated tables. I'm not very good with SQL, but I ASSUME that using an IN statement and not joining these tables together is probably the least efficient way I can do this, but I don't know enough to ask anything but "how do I do this better?" If possible, I would like to do this all in my stored procedure using a query to gather all the IDs except for the five 'newest', then delete them. Another twist, run entries can be marked save (save = 1) and should not be deleted. The RunHistory table looks like this: CREATE TABLE `TAA`.`RunHistory` ( `id` int(11) NOT NULL auto_increment, `start_time` datetime default NULL, `stop_time` datetime default NULL, `config_id` int(11) NOT NULL, [...] `save` tinyint(1) NOT NULL default '0', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=0 DEFAULT CHARSET=utf8;

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• Application Design: Single vs. Multiple Hits to the DB

  - by shyneman

  I'm building a service that performs a set of configured activities based on the type of request that it receives. Each activity involves going to the database and retrieving/updating some kind of information. The logic for each activity can be generalized and re-used across different request types. The activities may need to participate in a transaction for the duration of the servicing the request. One option, I'm considering is having each activity maintain its own access to DAL/database. This fully encapsulates the activity into a stand-alone re-usable piece, but hitting the database multiple times for one request doesn't seem like a viable option. I don't really know how to easily implement the concept of a transaction across the multiple activities here either. The second option is to encapsulate ALL the activities into one big activity and hit the database once. But this does not allow re-use and configuration of these activities for different requests. Does anyone have any suggestions and input about what should be the best way to approach my problem? Thanks for any help.

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• paged list with checkboxes, keep the checkbox value browsing through the paging?

  - by Dejan.S

  Hi. I got a list of customers I thought I would list in a gridview or a repeater with customer html, it gone have paging. I'm gone have a checkbox for each customer in the list. Do you guys have any suggestions on how I should do to keep the checkbox value when I go to page 2-3-4 ect in the paging. I'm thinking a session to store the id of the checked customers. After I'm done setting the values they go to the database. Do you got any other ideas then the session I'm thinking of? thanks guys

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• Premature optimization is the root of all evil, but can it ever be too late?

  - by polygenelubricants

  "We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil" So what is that 3% like? Can the avoidance of premature optimization ever be taken too extreme that it does more harm than good? Even if it's rare, has there been a case of a real measurable software engineering disaster due to complete negligence to optimize early in the process? Bonus question: is software engineering pretty much the only field that has such a counter intuitive principle regarding doing something earlier rather than later before things potentially become too big a problem to fix? Personal question: how do you justify something as premature optimization and not just a case of you being lazy/ignorant/dumb?

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• MVC (model-view-controller) - can it be explained in simple terms?

  - by DVK

  I need to explain to a not-very-technical manager the MVC (model-view-controller) concept and ran into trouble. The problem is that the explanation needs to be on a "your grandma will get it" level - e.g. even the fairly straightforward explanation offered on MVC Wiki page didn't work, at least with my commentary. Does anyone have a reference to a good MVC explanation in simple terms? It would ideally be done with non-techie metaphor examples (e.g. similar to "Decorator pattern is like glasses") - one reason I failed was that all MVC examples I could come up with were development related. I once saw a list of pattern explanations but to the best of my memory MVC was not on it. Thanks!

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• asp.mvc model design

  - by Radu D

  Hi, I am pretty new to MVC and I am looking for a way to design my models. I have the MVC web site project and another class library that takes care of data access and constructing the business objects. If I have in that assembly a class named Project that is a business object and I need to display all projects in a view ... should I make another model class Project? In this case the classes will be identical. Do I gain something from doing a new model class? I don't like having in views references to objects from another dll ... but i don't like duplicating the code neither. Did you encounter the same problem?

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• Which design pattern is most appropriate?

  - by Anon

  Hello, I want to create a class that can use one of four algorithms (and the algorithm to use is only known at run-time). I was thinking that the Strategy design pattern sounds appropriate, but my problem is that each algorithm requires slightly different parameters. Would it be a bad design to use strategy, but pass in the relevant parameters into the constructor?. Here is an example (for simplicity, let's say there are only two possible algorithms) ... class Foo { private: // At run-time the correct algorithm is used, e.g. a = new Algorithm1(1); AlgorithmInterface* a; }; class AlgorithmInterface { public: virtual void DoSomething = 0; }; class Algorithm1 : public AlgorithmInterface { public: Algorithm1( int i ) : value(i) {} virtual void DoSomething(){ // Does something with int value }; int value; }; class Algorithm2 : public AlgorithmInterface { public: Algorithm2( bool b ) : value(b) {} virtual void DoSomething(){ // Do something with bool value }; bool value; };

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• Server Emulator Design Pattern

  - by adisembiring

  I wanna build server socket emulator, but I want implement some design pattern there. I will described my case study that I have simplified like these: My Server Socket will always listen client socket. While some request message come from the client socket, the server emulator will response the client through the socket. the response is response code. '00' will describe request message processed successfully, and another response code expect '00' will describe there are some error while processing the message request. IN the server there are some UI, this UI contain check response parameter such as. response code timeout interval While the server want to response the client message, the response code taken from input parameter response form UI check the timeout interval, it will create sleep thread and the interval taken from timeout interval input from UI. I have implement the function, but I create it in one class. I feel it so sucks. Can you suggest me what class / interface that I must create to refactor my code.

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• Should my internal API classes be all in one package?

  - by Chris

  I'm hard at work packaging up an API for public consumption. As such I'm trying to limit the methods that are exposed to only those that I wish to be public and supportable. Underneath this of course there are a multitude of limited access methods. The trouble is that I have a lot of internal code that needs to access these restricted methods without making those methods public. This creates two issues: I can't create interfaces to communicate between classes as this would make these my internal methods public. I can't access protected or default methods unless I put the majority of my internal classes in the same package. So, I have around 70 or 80 internal classes in cleanly segregated packages BUT with overly permissive access modifiers. Would you say that a single package is the lesser of two evils or is there a better way to be able to mask my internal methods whilst keeping more granular packages? I'd be interested to find out the best practice here. I'm already aware of This

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• How do I put an ASP.NET website project and class library projects in one .sln file on Subversion

  - by JustinP8

  My company has several class libraries we use in multiple website projects (not web application projects). Website projects don't have .sln files, but I'm sure I've read in my past research that you can make a blank solution and put your website and class library projects in it. After answers to my previous questions, this is the direction that I'm going (based slightly on [http://amadiere.com/blog/2009/06/multiple-subversion-projects-in-one-visual-studio-solution-using-svnexternals/][1]: /websites /website1 /trunk /website1 /libraries /library1 /trunk /library1 /library2 /trunk /library2 /etc... Then I planed on using svn:externals to copy /library1, /library2, and so on into the working_copy/websites/website1/ folder. I want my team members to be able to checkout the /trunk folder for website1 and get a .sln file, /library1 external, /library2 external, etc. I want that .sln file to contain the website1 website project, and all of the library external projects. Hopefully that would look something like: /working_copy /websites /website1 /trunk /website1 /library1 (svn:external of libraries/library1/trunk/library1) /library2 (svn:external of libraries/library2/trunk/library2) /etc. website1.sln So, at the end of all of this, the goal is that my teammates check out the trunk, open the solution, and everyone has the exact same solution. When we commit, everything is committed appropriately to subversion (the website code, and the libraries are committed to their appropriate place on the repo). How have others solved these issues? How can I make a .sln file that my team members and I can share in this manner? [1]: "This Article"

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• best practice for passing many arguments to method ?

  - by Tony

  Occasionally , we have to write methods that receive many many arguments , for example : public void doSomething(Object objA , Object objectB ,Date date1 ,Date date2 ,String str1 ,String str2 ) { } When I encounter this kind of problem , I often encapsulate arguments into a map. Map<Object,Object> params = new HashMap<Object,Object>(); params.put("objA",ObjA) ; ...... public void doSomething(Map<Object,Object> params) { // extracting params Object objA = (Object)params.get("objA"); ...... } This is not a good practice , encapsulate params into a map is totally a waste of efficiency. The good thing is , the clean signature , easy to add other params with fewest modification . what's the best practice for this kind of problem ?

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• Architecting ASP.net MVC App to use repositories and services

  - by zaladane

  Hello, I recently started reading about ASP.net MVC and after getting excited about the concept, i started to migrate all my webform project to MVC but i am having a hard time keeping my controller skinny even after following all the good advices out there (or maybe i just don't get it ... ). The website i deal with has Articles, Videos, Quotes ... and each of these entities have categories, comments, images that can be associated with it. I am using Linq to sql for database operations and for each of these Entities, i have a Repository, and for each repository, i create a service to be used in the controller. so i have - ArticleRepository ArticleCategoryRepository ArticleCommentRepository and the corresponding service ArticleService ArticleCategoryService ... you see the picture. The problem i have is that i have one controller for article,category and comment because i thought that having ArticleController handle all of that might make sense, but now i have to pass all of the services needed to the Controller constructor. So i would like to know what it is that i am doing wrong. Are my services not designed properly? should i create Bigger service to encapsulate smaller services and use them in my controller? or should i have an articleCategory Controller and an articleComment Controller? A page viewed by the user is made of all of that, thee article to be viewed,the comments associated with it, a listing of the categories to witch it applies ... how can i efficiently break down the controller to keep it "skinny" and solve my headache? Thank you! I hope my question is not too long to be read ...

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• What are Code Smells? What is the best way to correct them?

  - by Rob Cooper

  OK, so I know what a code smell is, and the Wikipedia Article is pretty clear in its definition: In computer programming, code smell is any symptom in the source code of a computer program that indicates something may be wrong. It generally indicates that the code should be refactored or the overall design should be reexamined. The term appears to have been coined by Kent Beck on WardsWiki. Usage of the term increased after it was featured in Refactoring. Improving the Design of Existing Code. I know it also provides a list of common code smells. But I thought it would be great if we could get clear list of not only what code smells there are, but also how to correct them. Some Rules Now, this is going to be a little subjective in that there are differences to languages, programming style etc. So lets lay down some ground rules: ** ONE SMELL PER ANSWER PLEASE! & ADVISE ON HOW TO CORRECT! ** See this answer for a good display of what this thread should be! DO NOT downmod if a smell doesn't apply to your language or development methodology We are all different. DO NOT just quickly smash in as many as you can think of Think about the smells you want to list and get a good idea down on how to work around. DO downmod answers that just look rushed For example "dupe code - remove dupe code". Let's makes it useful (e.g. Duplicate Code - Refactor into separate methods or even classes, use these links for help on these common.. etc. etc.). DO upmod answers that you would add yourself If you wish to expand, then answer with your thoughts linking to the original answer (if it's detailed) or comment if its a minor point. DO format your answers! Help others to be able to read it, use code snippets, headings and markup to make key points stand out!

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• HTTP_HOST vs. SERVER_NAME

  - by Emanuil

  When would you consider using one over the other and why?

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• Create swipe controlled simple flipbook style animation in ObjC

  - by eco_bach

  Hi I am a beginner in Obj C development, though quite experienced (over 10 years) with other ECMAscript based languages and OOP development. I want to build a simple flipbook style animation, controlled through swiping motion. I'm sure extremely simple for any advanced ObjC coders. Can anyone with extensive ObjC-CocoaTouch experience give me some higher level recommendations? ie, 1 -general application design, should I start with a simple view based application, or navigation based or? 2 -should I use 3rd party animation frameworks such as Cocos2D, or stick with built in classes and methods? 3 -if using built in methods, classes, what is the recommended way of achieving a animation, that will be controlled via swipe and touch gestures? 4 -I want to eventually have multiple 'flipbooks' that I can 'instantly' swap with one another, ie to give the net effect of an object changing color, etc, but not sure how to approach this from a memory management point of view, related to #1 above Except for point 3 above, I'm not expecting any actual code examples. Just general guidelines to follow and perhaps, what are some next steps I should take in my goal as an ObjC code samurai.

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• How to best launch C++ application from web page

  - by JB

  I guess there are two parts to this question, one technical and one best practice for security and doing things "right". I'm working on a little game using C++ / directx but I would like to be able to launch it from a web page by someone clicking on a link on that page. Ideally I would like the first time they clicked for it to launch an installer downloads and installs the game on their machine, and then the next time to launch an application which updates the game from a web site if it's old and then launches it. I have no problems with the expected security popups and questions the first time it runs. I want people to be certain what they are installing and understand what they are doing. But it would be nice if once it is installed they could run it with the minimum of fuss. My question then is what technologies I could use to do this? I'm thinking that it would need a browser plugin and an activex control so that first time you'd install that, and subsequently the control/plugin would be able to launch the game. I'm not sure that under newer browser secuity models that a plugin would have the permissions to be able to run an installer though or silently invoke applications on the client machine even if they are already installed. Is there a more sensible way to achive what I want to achieve? And I'm worried about the security aspects too. I want this to be convenient for users but I of course want to do it "right". I know this can be done as I've seen several mmorpg type games that launch in this way from the browser now but it's not entirely clear to me how they've done it.

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• How should the Version field be used in Trac?

  - by Eric

  I use Trac to track bugs, and future changes in my software projects. Tickets in Trac have a "Version" field and I'm trying to figure out the best way to use this field. Say I find a series of bugs in version 1.0 of my software. I create tickets in track for each and assign them to version 1.0. Now say I fix some of the bugs, and add some of the new features and release version 1.1. But some of the old 1.0 bugs are still in 1.1. Should I change their corresponding tickets to version 1.1 because they also now exist in 1.1? Or should I leave them set to version 1.0 as a way of tracking what version the bug was found in, and just assume that any open tickets in older versions still exist in newer versions?

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• Python and the Singleton Pattern

  - by dmanxiii

  What is the best way to implement the singleton pattern in Python? It seems impossible to declare the constructor private or protected as is normally done with the Singleton pattern...

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• View artifacts leaking into the model of MVC

  - by Jono

  In an ASP.NET MVC application (which has very little chance of having its view technology ported to something non-HTML, but whose functional requirements evolve weekly,) how much HTML should ideally be allowed to be directly represented in the Model? I might come across as a design bigot for this, but I regard it as bad practice to allow any view constructs to "leak" into the model in an MVC application (and vice versa). For example, a Model that represents an item you're about to purchase should know nothing about the HTML check box that says "add giftwrap/message", nor should it know about any HTML drop down lists for payment card types. Conversely the View shouldn't be doing work like figuring out button text by translating keys into values (by looking in resource files.)

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• c++ Design pattern for CoW, inherited classes, and variable shared data?

  - by krunk

  I've designed a copy-on-write base class. The class holds the default set of data needed by all children in a shared data model/CoW model. The derived classes also have data that only pertains to them, but should be CoW between other instances of that derived class. I'm looking for a clean way to implement this. If I had a base class FooInterface with shared data FooDataPrivate and a derived object FooDerived. I could create a FooDerivedDataPrivate. The underlying data structure would not effect the exposed getters/setters API, so it's not about how a user interfaces with the objects. I'm just wondering if this is a typical MO for such cases or if there's a better/cleaner way? What peeks my interest, is I see the potential of inheritance between the the private data classes. E.g. FooDerivedDataPrivate : public FooDataPrivate, but I'm not seeing a way to take advantage of that polymorphism in my derived classes. class FooDataPrivate { public: Ref ref; // atomic reference counting object int a; int b; int c; }; class FooInterface { public: // constructors and such // .... // methods are implemented to be copy on write. void setA(int val); void setB(int val); void setC(int val); // copy constructors, destructors, etc. all CoW friendly private: FooDataPrivate *data; }; class FooDerived : public FooInterface { public: FooDerived() : FooInterface() {} private: // need more shared data for FooDerived // this is the ???, how is this best done cleanly? };

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