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• Code Design Process?

  - by user156814

  I am going to be working on a project, a web application. I was reading 37signals getting real pamphlet online (http://gettingreal.37signals.com/), and I understand the recommended process to build the entire website. Brainstorm, sketch, HTML, code. They touch on each process lightly, but they never really talk much about the coding process (all they say is to keep code lean). I've been reading about different ways to go about it (top to bottom, bottom to top) but I dont know much about each way. I even read somewhere that one should write tests for the code before they actually write the code??? WHAT? What coding process should one follow when building an application. if its necessary, I'm using PHP and a framework.

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• What are some good ways to write PHP application with modules support?

  - by Gabriel

  Hi, I'm starting to write a application in php with one of my friends and was wondering, if you have any advice on how to implement module support into our application. Or is there a way how to automatically load modules written in php by a php application? Or should i just rely on __autoload function? And we are not using any kind of framework, for now at least.

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• Java interface and abstract class issue

  - by George2

  Hello everyone, I am reading the book -- Hadoop: The Definitive Guide, http://www.amazon.com/Hadoop-Definitive-Guide-Tom-White/dp/0596521979/ref=sr_1_1?ie=UTF8&s=books&qid=1273932107&sr=8-1 In chapter 2 (Page 25), it is mentioned "The new API favors abstract class over interfaces, since these are easier to evolve. For example, you can add a method (with a default implementation) to an abstract class without breaking old implementations of the class". What does it mean (especially what means "breaking old implementations of the class")? Appreciate if anyone could show me a sample why from this perspective abstract class is better than interface? thanks in advance, George

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• What real life good habits has programming given you?

  - by Luca

  Following this question, what real life good habits has programming given you?

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• What should I name my files with generic class definitions?

  - by Tomas Lycken

  I'm writing a couple of classes that all have generic type arguments, but I need to overload the classes because I need a different number of arguments in different scenarios. Basically, I have public class MyGenericClass<T> { ... } public class MyGenericClass<T, K> { ... } public class MyGenericClass<T, K, L> { ... } // it could go on forever, but it won't... I want them all in the same namespace, but in one source file per class. What should I name the files? Is there a best practice?

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• How to allow for modular development while still running in same JVM?

  - by Marcus

  Our current app runs in a single JVM. We are now splitting up the app into separate logical services where each service runs in its own JVM. The split is being done to allow a single service to be modified and deployed without impacting the entire system. This reduces the need to QA the entire system - just need to QA the interaction with the service being changed. For interservice communication we use a combination of REST, an MQ system bus, and database views. What I don't like about this: REST means we have to marshal data to/from XML DB views couple the systems together which defeats the whole concept of separate services MQ / system bus is added complexity There is inevitably some code duplication between services You have set up n JBoss server configurations, we have to do n number of deployments, n number of set up scripts, etc, etc. Is there a better way to structure an internal application to allow modular development and deployment while allowing the app to run in a single JVM (and achieving the associated benefits)?

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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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• MVC pattern implementation. What is the n-relation between its components

  - by Srodriguez

  Dear all, I'm working in a C# project and we are , in order to get some unity across the different parts of our UI, trying to use the MVC pattern. The client is windows form based and I'm trying to create a simple MVC pattern implementation. It's been more challenging than expected, but I still have some questions regarding the MVC pattern. The problem comes mostly from the n-n relationships between its components: Here is what I've understood, but I'm not sure at all of it. Maybe someone can correct me? Model: can be shared among different Views. 1-n relationship between Model-View View: shows the state of the model. only one controller (can be shared among different views?). 1-1 relationship with the Model, 1-1 relationship with the controller Controller: handles the user actions on the view and updates the model. One controller can be shared among different views, a controller interacts only with one model? I'm not sure about the two last ones: Can a view have several controller? Or can a view share a controller with another view? Or is it only a 1:1 relationship? Can a controller handle several views? can it interact with several models? Also, I take advantage of this question to ask another MVC related question. I've suppressed all the synchronous calls between the different members of the MVC, making use of the events and delegates. One last call is still synchronous and is actually the most important one: The call between the view and the controller is still synchronous, as I need to know rather the controller has been able to handle the user's action or not. This is very bad as it means that I could block the UI thread (hence the client itself) while the controller is processing or doing some work. How can I avoid this? I can make use of the callback but then how do i know to which event the callback comes from? PS: I can't change the pattern at this stage, so please avoid answers of type "use MVP or MVVC, etc ;) Thanks!

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• MVC pattern implementation. What is the n-relation between its components

  - by Srodriguez

  Dear all, I'm working in a C# project and we are , in order to get some unity across the different parts of our UI, trying to use the MVC pattern. The client is windows form based and I'm trying to create a simple MVC pattern implementation. It's been more challenging than expected, but I still have some questions regarding the MVC pattern. The problem comes mostly from the n-n relationships between its components: Here is what I've understood, but I'm not sure at all of it. Maybe someone can correct me? Model: can be shared among different Views. 1-n relationship between Model-View View: shows the state of the model. only one controller (can be shared among different views?). 1-1 relationship with the Model, 1-1 relationship with the controller Controller: handles the user actions on the view and updates the model. One controller can be shared among different views, a controller interacts only with one model? I'm not sure about the two last ones: Can a view have several controller? Or can a view share a controller with another view? Or is it only a 1:1 relationship? Can a controller handle several views? can it interact with several models? Also, I take advantage of this question to ask another MVC related question. I've suppressed all the synchronous calls between the different members of the MVC, making use of the events and delegates. One last call is still synchronous and is actually the most important one: The call between the view and the controller is still synchronous, as I need to know rather the controller has been able to handle the user's action or not. This is very bad as it means that I could block the UI thread (hence the client itself) while the controller is processing or doing some work. How can I avoid this? I can make use of the callback but then how do i know to which event the callback comes from? PS: I can't change the pattern at this stage, so please avoid answers of type "use MVP or MVVC, etc ;) Thanks!

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• Is there a difference here?

  - by HotHead

  Please consider following code: 1. uint16 a = 0x0001; if(a < 0x0002) { // do something } 2. uint16 a = 0x0001; if(a < uint16(0x0002)) { // do something } 3. uint16 a = 0x0001; if(a < static_cast<uint16>(0x0002)) { // do something } 4. uint16 a = 0x0001; uint16 b = 0x0002; if(a < b) { // do something } What compiler does in backgorund and what is the best (and correct) way to do above testing? p.s. sorry, but I couldn't find the better title :) Thank you in advance!

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• Should java try blocks be scoped as tightly as possible?

  - by isme

  I've been told that there is some overhead in using the Java try-catch mechanism. So, while it is necessary to put methods that throw checked exception within a try block to handle the possible exception, it is good practice performance-wise to limit the size of the try block to contain only those operations that could throw exceptions. I'm not so sure that this is a sensible conclusion. Consider the two implementations below of a function that processes a specified text file. Even if it is true that the first one incurs some unnecessary overhead, I find it much easier to follow. It is less clear where exactly the exceptions come from just from looking at statements, but the comments clearly show which statements are responsible. The second one is much longer and complicated than the first. In particular, the nice line-reading idiom of the first has to be mangled to fit the readLine call into a try block. What is the best practice for handling exceptions in a funcion where multiple exceptions could be thrown in its definition? This one contains all the processing code within the try block: void processFile(File f) { try { // construction of FileReader can throw FileNotFoundException BufferedReader in = new BufferedReader(new FileReader(f)); // call of readLine can throw IOException String line; while ((line = in.readLine()) != null) { process(line); } } catch (FileNotFoundException ex) { handle(ex); } catch (IOException ex) { handle(ex); } } This one contains only the methods that throw exceptions within try blocks: void processFile(File f) { FileReader reader; try { reader = new FileReader(f); } catch (FileNotFoundException ex) { handle(ex); return; } BufferedReader in = new BufferedReader(reader); String line; while (true) { try { line = in.readLine(); } catch (IOException ex) { handle(ex); break; } if (line == null) { break; } process(line); } }

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• C++ interpreter conceptual problem

  - by Jan Wilkins

  I've built an interpreter in C++ for a language created by me. One main problem in the design was that I had two different types in the language: number and string. So I have to pass around a struct like: class myInterpreterValue { myInterpreterType type; int intValue; string strValue; } Objects of this class are passed around million times a second during e.g.: a countdown loop in my language. Profiling pointed out: 85% of the performance is eaten by the allocation function of the string template. This is pretty clear to me: My interpreter has bad design and doesn't use pointers enough. Yet, I don't have an option: I can't use pointers in most cases as I just have to make copies. How to do something against this? Is a class like this a better idea? vector<string> strTable; vector<int> intTable; class myInterpreterValue { myInterpreterType type; int locationInTable; } So the class only knows what type it represents and the position in the table This however again has disadvantages: I'd have to add temporary values to the string/int vector table and then remove them again, this would eat a lot of performance again. Help, how do interpreters of languages like Python or Ruby do that? They somehow need a struct that represents a value in the language like something that can either be int or string.

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• StockTrader RI > Controllers, Presenters, WTF?

  - by SandRock

  I am currently learning how to make advanced usage of WPF via the Prism (Composite WPF) project. I watch many videos and examples and the demo application StockTraderRI makes me ask this question: What is the exact role of each of the following part? SomethingService: Ok, this is something to manage data SomethingView: Ok, this is what's displayed SomethingPresentationModel: Ok, this contains data and commands for the view to bind to (equivalent to a ViewModel). SomethingPresenter: I don't really understand it's usage SomethingController: Don't understand too I saw that a Presenter and a Controller are not necessary but I would like to understand why they are here. Can someone tell me their role and when to use them?

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• Meta Search Engine Architecture

  - by Loki

  The question wasn't clear enough, I think; here's an updated straight to the point question: What are the common architectures used in building a meta search engine and is there any libraries available to build that type of search engine? I'm looking at building an "enterprise" type of search engine where the indexed data could be coming from proprietary (like Autonomy or a Google Box) or public search engines (like Google Web or Yahoo Web).

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• When to alter a function vs when to just write a new one...?

  - by Andrew Heath

  /is n00b Through the gift of knowledge and expertise encoded here, I am doing my best to avoid n00b mistakes as I learn the basics of programming. I use functions when I (think I) can in PHP, and keep them somewhat sorted in different includes. The n00b problem I'm running into now is situations where perhaps 4/5th of an existing function is relevant to a new need. Maybe there are a slightly different set of inputs, or an additional calculation or two in the series, or output needs a different format/structure... but the core of the function is still applicable. Is there a good rule of thumb regarding when one should bolt-on crap to an original function and when one should (literally) copy & paste most of it into a new function and tweak to fit the situation? On the one hand I feel bad duping code, on the other I feel bad cluttering up an existing function with stuff not always needed...

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• Interface and base class mix, the right way to implement this

  - by Lerxst

  I have some user controls which I want to specify properties and methods for. They inherit from a base class, because they all have properties such as "Foo" and "Bar", and the reason I used a base class is so that I dont have to manually implement all of these properties in each derived class. However, I want to have a method that is only in the derived classes, not in the base class, as the base class doesn't know how to "do" the method, so I am thinking of using an interface for this. If i put it in the base class, I have to define some body to return a value (which would be invalid), and always make sure that the overriding method is not calling the base. method Is the right way to go about this to use both the base class and an interface to expose the method? It seems very round-about, but every way i think about doing it seems wrong... Let me know if the question is not clear, it's probably a dumb question but I want to do this right.

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• How should Application.Run() be called for the main presenter a MVP WinForms app?

  - by Mr Roys

  I'm learning to apply MVP to a simple WinForms app (only one form) in C# and encountered an issue while creating the main presenter in static void Main(). Is it a good idea to expose a View from the Presenter in order to supply it as a parameter to Application.Run()? Currently, I've implemented an approach which allows me to not expose the View as a property of Presenter: static void Main() { IView view = new View(); Model model = new Model(); Presenter presenter = new Presenter(view, model); presenter.Start(); Application.Run(); } The Start and Stop methods in Presenter: public void Start() { view.Start(); } public void Stop() { view.Stop(); } The Start and Stop methods in View (a Windows Form): public void Start() { this.Show(); } public void Stop() { // only way to close a message loop called // via Application.Run(); without a Form parameter Application.Exit(); } The Application.Exit() call seems like an inelegant way to close the Form (and the application). The other alternative would be to expose the View as a public property of the Presenter in order to call Application.Run() with a Form parameter. static void Main() { IView view = new View(); Model model = new Model(); Presenter presenter = new Presenter(view, model); Application.Run(presenter.View); } The Start and Stop methods in Presenter remain the same. An additional property is added to return the View as a Form: public void Start() { view.Start(); } public void Stop() { view.Stop(); } // New property to return view as a Form for Application.Run(Form form); public System.Windows.Form View { get { return view as Form(); } } The Start and Stop methods in View (a Windows Form) would then be written as below: public void Start() { this.Show(); } public void Stop() { this.Close(); } Could anyone suggest which is the better approach and why? Or there even better ways to resolve this issue?

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• Designing a class in such a way that it doesn't become a "God object"

  - by devoured elysium

  I'm designing an application that will allow me to draw some functions on a graphic. Each function will be drawn from a set of points that I will pass to this graphic class. There are different kinds of points, all inheriting from a MyPoint class. For some kind of points it will be just printing them on the screen as they are, others can be ignored, others added, so there is some kind of logic associated to them that can get complex. How to actually draw the graphic is not the main issue here. What bothers me is how to make the code logic such that this GraphicMaker class doesn't become the so called God-Object. It would be easy to make something like this: class GraphicMaker { ArrayList<Point> points = new ArrayList<Point>(); public void AddPoint(Point point) { points.add(point); } public void DoDrawing() { foreach (Point point in points) { if (point is PointA) { //some logic here else if (point is PointXYZ) { //...etc } } } } How would you do something like this? I have a feeling the correct way would be to put the drawing logic on each Point object (so each child class from Point would know how to draw itself) but two problems arise: There will be kinds of points that need to know all the other points that exist in the GraphicObject class to know how to draw themselves. I can make a lot of the methods/properties from the Graphic class public, so that all the points have a reference to the Graphic class and can make all their logic as they want, but isn't that a big price to pay for not wanting to have a God class?

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• Should a function have only one return statement?

  - by David

  Are there good reasons why it's a better practice to have only one return statement in a function? Or is it okay to return from a function as soon as it is logically correct to do so, meaning there may be many return statements in the function?

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• How can I make a family of singletons?

  - by Jay

  I want to create a set of classes that share a lot of common behavior. Of course in OOP when you think that you automatically think "abstract class with subclasses". But among the things I want these classes to do is to each have a static list of instances of the class. The list should function as sort of a singleton within the class. I mean each of the sub-classes has a singleton, not that they share one. "Singleton" to that subclass, not a true singleton. But if it's a static, how can I inherit it? Of course code like this won't work: public abstract A { static List<A> myList; public static List getList() { if (myList==null) myList=new ArrayList<A>(10); return myList; } public static A getSomethingFromList() { List listInstance=getList(); ... do stuff with list ... } public int getSomethingFromA() { ... regular code acting against current instance ... } } public class A1 extends A { ... } public class A2 extends A { ... } A1 somethingfromA1List=(A1) A1.getSomethingFromList(); A2 somethingfromA2List=(A2) A2.getSomethingFromList(); The contents of the list for each subclass would be different, but all the code to work on the lists would be the same. The problem with the above code is that I'd only have one list for all the subclasses, and I want one for each. Yes, I could replicate the code to declare the static list in each of the subclasses, but then I'd also have to replicate all the code that adds to the lists and searches the list, etc, which rather defeats the purpose of subclassing. Any ideas on how to do this without replicating code?

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• Events and references pattern

  - by serhio

  In a project I have the following relation between BO and GUI By e.g. G could represent a graphic with time lines, C a TimeLine curve, P - points of that curve and T the time that represents each point. Each GUI object is associated with the BO corresponding object. When T changes GUI P captures the Changed event and changes its location. So, when G should be modified, it modifies internally its objects and as result T changes, P moves and the GuiG visually changes, everything is OK. But there is an inconvenient of this architecture... BO should not be recreated, because this will breack the link between BO and GUIO. In particular, GUI P should always have the same reference of T. If in a business logic I do by e.g. P1.T = new T(this.T + 10) GUI_P1 will not move anymore, because it wait an event from the reference of former P1.T object, that does not belongs to P1 anymore. So the solution was to always modify the existing objects, not to recreate it. But here is an other inconvenient: performance. Say I have a ready newC object that should replace the older one. Instead of doing G1.C = newC I should do foreach T in foreach P in C replace with T from P from newC. Is there an other more optimal way to do it?

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• Best practice with respect to NPE and multiple expressions on single line

  - by JRL

  I'm wondering if it is an accepted practice or not to avoid multiple calls on the same line with respect to possible NPEs, and if so in what circumstances. For example: getThis().doThat(); vs Object o = getThis(); o.doThat(); The latter is more verbose, but if there is an NPE, you immediately know what is null. However, it also requires creating a name for the variable and more import statements. So my questions around this are: Is this problem something worth designing around? Is it better to go for the first or second possibility? Is the creation of a variable name something that would have an effect performance-wise? Is there a proposal to change the exception message to be able to determine what object is null in future versions of Java ?

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• how to wrap a function that only takes individual elements to make it take a list

  - by stevejb

  Hello, Say I have a function handed to me that I cannot change and must use as is. This function takes several objects in the form of oldFunction( object1, object2, object3, ...) where ... are other arguments. I want to write a wrapper to take a list of objects. My idea was this. sjb.ListWrapper <- function(myList,...) { lLen <- length(myList) myStr <- "" for( i in 1:lLen) { myStr <- paste(myStr, "myList[[", i , "]],",sep="") } myCode <- paste("oldFunction(", myStr, "...)") eval({myCode}) } However, the issue is that I want to use this from Sweave and I need the output of oldFunction to be printed. What is the right way to do this? Thanks.

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• Use database field maxlength as html layout input maxlength best practice. asp.net mvc

  - by Andrew Florko

  Hello everybody, There are string length limitations in database structure (email is declared as nvarchar[30] for instance) There are lots of html forms that has input textbox fields that should be limited in length for that reason. What is the best practice to synchronize database fields and html layout input fields length limitations ? Can it be done automatically (html layout input fields declared the same max length as database data they represent)? Thank you in advance.

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• Best approach to design a service oriented system

  - by Gustavo Paulillo

  Thinking about service orientation, our team are involved on new application designs. We consist in a group of 4 developers and a manager (that knows something about programming and distributed systems). Each one, having own opinion on service design. It consists in a distributed system: a user interface (web app) accessing the services in a dedicated server (inside the firewall), to obtain the business logic operations. So we got 2 main approachs that I list above : Modular services Having many modules, each one consisting of a service (WCF). Example: namespaces SystemX.DebtService, SystemX.CreditService, SystemX.SimulatorService Unique service All the business logic is centralized in a unique service. Example: SystemX.OperationService. The web app calls the same service for all operations. In your opinion, whats the best? Or having another approach is better for this scenario?

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