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  • State Pattern - should a state know about its context?

    - by Extrakun
    I am referring to the state pattern as described in this link. In the example class diagram, a context has numerous states. However, it does not show how does a state communicates with a context (perhaps an input in a state has impact on a setting in the context). The two examples on the page shows either passing the context to the state via a function, or storing a reference to the context. Are those advisable? Are there other ways for a state to communicate with a context? Update to an edit: For instance, I am doing a remote control which can have several states. Say, the context has a setting for Volume, and I am in one of the states which allow me to tweak the volume. How should the state communicates with the context that the volume is being changed?

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  • Do you leverage the benefits of the open-closed principle?

    - by Kaleb Pederson
    The open-closed principle (OCP) states that an object should be open for extension but closed for modification. I believe I understand it and use it in conjunction with SRP to create classes that do only one thing. And, I try to create many small methods that make it possible to extract out all the behavior controls into methods that may be extended or overridden in some subclass. Thus, I end up with classes that have many extension points, be it through: dependency injection and composition, events, delegation, etc. Consider the following a simple, extendable class: class PaycheckCalculator { // ... protected decimal GetOvertimeFactor() { return 2.0M; } } Now say, for example, that the OvertimeFactor changes to 1.5. Since the above class was designed to be extended, I can easily subclass and return a different OvertimeFactor. But... despite the class being designed for extension and adhering to OCP, I'll modify the single method in question, rather than subclassing and overridding the method in question and then re-wiring my objects in my IoC container. As a result I've violated part of what OCP attempts to accomplish. It feels like I'm just being lazy because the above is a bit easier. Am I misunderstanding OCP? Should I really be doing something different? Do you leverage the benefits of OCP differently? Update: based on the answers it looks like this contrived example is a poor one for a number of different reasons. The main intent of the example was to demonstrate that the class was designed to be extended by providing methods that when overridden would alter the behavior of public methods without the need for changing internal or private code. Still, I definitely misunderstood OCP.

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  • How to organize a Coding Dojo?

    - by Stephan
    Over on stack overflow it was asked how to organize a coding dojo (http://stackoverflow.com/questions/4338567/how-to-organize-a-coding-dojo-event). I believe that may have been the wrong forum... I wonder the same thing: how is a Codeing Dojo organized? What is the structure of a meeting? How would one pick Katas? What do you plan ahead of time? I am interested in any ideas on this as well as links to any resource that may be outlining this.

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  • prism and multiple screens

    - by Avi
    OK - I am studying Prism a little because of a "free weekend" offer on Pluralsight. As this is proving too complex for me, I went to the Prism book and looked at the forward, and this is what it said: What comes after “Hello, World?” WPF and Silverlight developers are blessed with an abundance of excellent books... There’s no lack of tutorials on Model-View-ViewModel ... But they stop short of the guidance you need to deliver a non-trivial application in full. Your first screen goes well. You add a second screen and a third. Because you started your solution with the built-in “Navigation Application Template,” adding new screens feels like hanging shirts on a closet rod. You are on a roll. Until the harsh reality of real application requirements sets in. As it happens, your application has 30 screens not three. There’s no room on that closet rod for 30 screens. Some screens are modal pop-ups; you don’t navigate to a pop-up. Screens become interdependent such that user activity in one screen triggers changes that propagate throughout the UI. Some screens are optional; others are visible only to authorized users. Some screens are permanent, while other screens can be opened and closed at will. You discover that navigating back to a previously displayed screen creates a new instance. That’s not what you expected and, to your horror, the prior instance is gone along with the user’s unsaved changes. Now the issue is, I don't relate to this description. I've never been a UI programmer, but same as everyone else I'm using Windows apps such as MS-Office, and web sites such as Amazon, Facebook and StackExchange. And I look at these and I don't see many "so many screens" issues! Indeed, the only applications having many windows I can think of is Visual Studio. Maybe also Visio, a little. But take Word - You have a ribbon and a main window. Or take Facebook: You have those lists on the left (Favorites, Lists, Groups etc.), the status middle, the adds and then the Contacts sidebar. But it's only one page. Of course, I understand that in enterprise scenarios there are dashboad applications where multiple segments of the screen are updated from multiple non-related services. This I dig. But other scenarios? So - What am I missing? What is the "multiple screens" monster Pirsm is supposed to be the silver bullet solution for? Shoud I invest in studying Prism in addition to learning WPF or ASP.NET MVC?

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  • Is it bad practise to call a controller action from a view that was rendered by another controller?

    - by marco-fiset
    Let's say I have an OrderController which handles orders. The user adds products to it through the view, and then the final price gets calculated through an AJAX call to a controller action. The price calculation logic is implemented in a seperate class and used in a controller action. What happens is that I have many views from different controllers that need to use that particular action. I'd like to have some kind of a PriceController that I could call an action on. But then the view would have to know about that PriceController and call an action on it. Is it bad practice for a view to call an action on a different controller from which it was rendered?

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  • How to implment the database for event conditions and item bonuses for a browser based game

    - by Saifis
    I am currently creating a browser based game, and was wondering what was the standard approach in making diverse conditions and status bonuses database wise. Currently considering two cases. Event Conditions Needs min 1000 gold Needs min Lv 10 Needs certain item. Needs fulfillment of another event Status Bonus Reduces damage by 20% +100 attack points Deflects certain type of attack I wish to be able to continually change these parameters during the process of production and operation, so having them hard-coded isn't the best way. All I could come up with are the following two methods. Method 1 Create a table that contains each conditions with needed attributes Have a model named conditions with all the attributes it would need to set them conditions condition_type (level, money_min, money_max item, event_aquired) condition_amount prerequisite_condition_id prerequisite_item_id Method 2 write it in a DSL form that could be interpreted later in the code Perhaps something like yaml, have a text area in the setting form and have the code interpret it. condition_foo: condition_type :level min_level: 10 condition_type :item item_id: 2 At current Method 2 looks to be more practical and flexible for future changes, trade off being that all the flex must be done on the code side. Not to sure how this is supposed to be done, is it supposed to be hard coded? separate config file? Any help would be appreciated. Added For additional info, it will be implemented with Ruby on Rails

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  • Design pattern: static function call with input/output containers?

    - by Pavlo Dyban
    I work for a company in software research department. We use algorithms from our real software and wrap them so that we can use them for prototyping. Every time an algorithm interface changes, we need to adapt our wrappers respectively. Recently all algorithms have been refactored in such a manner that instead of accepting many different inputs and returning outputs via referenced parameters, they now accept one input data container and one output data container (the latter is passed by reference). Algorithm interface is limited to a static function call like that: class MyAlgorithm{ static bool calculate(MyAlgorithmInput input, MyAlgorithmOutput &output); } This is actually a very powerful design, though I have never seen it in a C++ programming environment before. Changes in the number of parameters and their data types are now encapsulated and they don't change the algorithm callback. In the latest algorithm which I have developed I used the same scheme. Now I want to know if this is a popular design pattern and what it is called.

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  • Can the following Domain Entity contain logic for creating/deleting other entities?

    - by user702769
    a) As far as I understand it, in most cases Domain Model DM doesn't contain code for creating/deleting domain entities, but instead it is the job of layers ( ie service layer or UI layer ) on top of DM to create/delete domain entities? b) Domain entities are modelled after real world entities. Assuming particular real world entity being abstracted does have the functionality of creating/deleting other real world entities, then I assume the domain entity abstracting this real world entity could also contain logic for creating/deleting other entities? class RobotDestroyerCreator { ... void heavyThinking() { ... if(...) unitOfWork.registerDelete(robot); ... if(...) { var robotNew = new Robot(...); unitOfWork.registerNew(robotNew); { ... } } Thank you

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  • How to had operation with character/items on binary with concrete operations on C++?

    - by Piperoman
    I have the next problem. A item can had a lot of states: NORMAL = 0000000 DRY = 0000001 HOT = 0000010 BURNING = 0000100 WET = 0001000 COLD = 0010000 FROZEN = 0100000 POISONED= 1000000 A item can had some states at same time but not all of them Is impossible to be dry and wet at same time. If you COLD a WET item, it turns into FROZEN. If you HOT a WET item, it turns into NORMAL A item can be BURNING and POISON Etc. I have try to set binary flags to states, and use AND to set operation to combine different states, checking before if is possible or not to do it, or change to another status. Exist a concrete patron to solve this problem efficiently without had a interminable switch that check every states with everynew states? It is relative easy to check 2 different states, but if exist a third state it is not trivial to do.

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  • Design: How to model / where to store relational data between classes

    - by Walker
    I'm trying to figure out the best design here, and I can see multiple approaches, but none that seems "right." There are three relevant classes here: Base, TradingPost, and Resource. Each Base has a TradingPost which can offer various Resources depending on the Base's tech level. Where is the right place to store the minimum tech level a base must possess to offer any given resource? A database seems like overkill. Putting it in each subclass of Resource seems wrong--that's not an intrinsic property of the Resource. Do I have a mediating class, and if so, how does it work? It's important that I not be duplicating code; that I have one place where I set the required tech level for a given item. Essentially, where does this data belong? P.S. Feel free to change the title; I struggled to come up with one that fits.

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  • Dependency Injection Confusion

    - by James
    I think I have a decent grasp of what Dependency Inversion principle (DIP) is, my confusion is more around dependency injection. My understanding is the whole point of DI is to decouple parts of an application, to allow changes in one part without effecting another, assuming the interface does not change. For examples sake, we have this public class MyClass(IMyInterface interface) { public MyClass { interface.DoSomething(); } } public interface IMyInterface { void DoSomething(); } How is this var iocContainer = new UnityContainer(); iocContainer.Resolve<MyClass>(); better practice than doing this //if multiple implementations are possible, could use a factory here. IMyInterface interface = new InterfaceImplementation(); var myClass = new MyClass(interface); It may be I am missing a very important point, but I am failing to see what is gained. I am aware that using an IOC container I can easily handle an objects life cycle, which is a +1 but I don't think that is core to what IOC is about.

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  • How to determine if class meets single responsibility principle ?

    - by user1483278
    Single Responsibility Principle is based on high cohesion principle. The difference between the two is that highly cohesive classes feature a set of responsibilities that are strongly related, while classes adhering to SRP have just one responsibility. But how do we determine whether particular class features a set of responsibilities and is thus just highly cohesive, or whether it has only one responsibility and is thus adhering to SRP? Namely, isn't it more or less subjective, since some may find class very granular ( and as such will consider a class as adhering to SRP ), while others may find it not granular enough?

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  • Am I bored with programming? [closed]

    - by user1167074
    I have started programming 2 years back and I have learnt web programming while working for big corporate companies. I was very passionate and I even did couple of side projects which were well appreciated by my friends and colleagues. But for the past 2 months I am not doing anything really interesting with programming, even if I get good ideas I am not feeling like coding, sub consciously I am feeling like "So What?" if I do this project. I would like to know from the more experienced programmers if this is just a phase or am I really missing something? Thanks

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  • Using allocators for different systems

    - by chadb
    I am going over the memory architecture for my game and even though I know my memory budgets may not be final, I at the point where I can start using them in a general sense. I know that I will need several allocators (for systems such as audio, rendering, etc) but I am unsure of how they will be accessed. I do not use singletons, so I can't just have something such as AudioManager::GetInstance().get_allocator(). Instead, I need to find a different method of usage but I am not sure of how. How can I store and call my allocators needed for several different systems over engine in an efficient manner?

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  • Using visitor pattern with large object hierarchy

    - by T. Fabre
    Context I've been using with a hierarchy of objects (an expression tree) a "pseudo" visitor pattern (pseudo, as in it does not use double dispatch) : public interface MyInterface { void Accept(SomeClass operationClass); } public class MyImpl : MyInterface { public void Accept(SomeClass operationClass) { operationClass.DoSomething(); operationClass.DoSomethingElse(); // ... and so on ... } } This design was, however questionnable, pretty comfortable since the number of implementations of MyInterface is significant (~50 or more) and I didn't need to add extra operations. Each implementation is unique (it's a different expression or operator), and some are composites (ie, operator nodes that will contain other operator/leaf nodes). Traversal is currently performed by calling the Accept operation on the root node of the tree, which in turns calls Accept on each of its child nodes, which in turn... and so on... But the time has come where I need to add a new operation, such as pretty printing : public class MyImpl : MyInterface { // Property does not come from MyInterface public string SomeProperty { get; set; } public void Accept(SomeClass operationClass) { operationClass.DoSomething(); operationClass.DoSomethingElse(); // ... and so on ... } public void Accept(SomePrettyPrinter printer) { printer.PrettyPrint(this.SomeProperty); } } I basically see two options : Keep the same design, adding a new method for my operation to each derived class, at the expense of maintainibility (not an option, IMHO) Use the "true" Visitor pattern, at the expense of extensibility (not an option, as I expect to have more implementations coming along the way...), with about 50+ overloads of the Visit method, each one matching a specific implementation ? Question Would you recommand using the Visitor pattern ? Is there any other pattern that could help solve this issue ?

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  • When should one use "out" parameters?

    - by qegal
    In Objective-C, there are several methods like initWithContentsOfFile:encoding:error: where one passes in a reference to an NSError object for the error: parameter. In this example, the value of the NSError object passed in can change based on what goes on at runtime when the method is being called and whether the body of the method was executed in a certain way successfully. In a way I think of this NSError object as sort of like a second return value from the method, and only differs from an object anObject in the statement return anObject; in that when this statement is called, execution leaves the method. So my question is, not only in the context of error handling in Objective-C, but in general, when should one use an "out" parameter in place of returning said value in a return statement?

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  • Pros and cons of creating a print friendly page to remove the use of pdfs?

    - by Phil
    the company I work for has a one page invoice that uses the library tcpdf. they wanted to do some design changes that I found are just incredibly difficult for setting up in .pdf format. Using html/css I could easily create the page and have it print very nicely, but I have a feeling that I am over looking something. What are the pros and cons of setting up a page just for printing? What are the pros and cons of putting out a .pdf? I could also use the CSS inline so that if they wanted to download it and open it they could.

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  • More than one way to skin an Audit

    - by BuckWoody
    I get asked quite a bit about auditing in SQL Server. By "audit", people mean everything from tracking logins to finding out exactly who ran a particular SELECT statement. In the really early versions of SQL Server, we didn't have a great story for very granular audits, so lots of workarounds were suggested. As time progressed, more and more audit capabilities were added to the product, and in typical database platform fashion, as we added a feature we didn't often take the others away. So now, instead of not having an option to audit actions by users, you might face the opposite problem - too many ways to audit! You can read more about the options you have for tracking users here: http://msdn.microsoft.com/en-us/library/cc280526(v=SQL.100).aspx  In SQL Server 2008, we introduced SQL Server Audit, which uses Extended Events to really get a simple way to implement high-level or granular auditing. You can read more about that here: http://msdn.microsoft.com/en-us/library/dd392015.aspx  As with any feature, you should understand what your needs are first. Auditing isn't "free" in the performance sense, so you need to make sure you're only auditing what you need to. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Can I include a robots meta tag outside of the head in HTML snippets indeded to be SSIed?

    - by Dan
    I have a number of files in my site which are not intended for independent viewing, but rather to be AJAXed into content within the site. They obviously don't meet HTML standards (no body, head, etc.) as independent entities. I would like to prevent search engines from indexing these pages, but do not have access to /robots.txt (which would be much more ideal). My question is, could I include the following at the top of these partial HTML files and get the desired results? <meta name="robots" content="noindex, noarchive"> I guess there are two parts to this question. Will this cause any rendering issues in any browsers? Will search engines (at least Google & Bing) interpret this as intended?

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  • Sucking Less Every Year ?

    - by AdityaGameProgrammer
    Sucking Less Every Year A trail of thought that had been on my mind for a while Quoting directly from the post I've often thought that sucking less every year is how humble programmers improve. You should be unhappy with code you wrote a year ago. If you aren't, that means either A) you haven't learned anything in a year, B) your code can't be improved, or C) you never revisit old code. All of these are the kiss of death for software developers. How often does this happen or not happen to you? How long before you see an actual improvement in your coding ? month, year? Do you ever revisit Your old code? How often does your old code plague you? or how often do you have to deal with your technical debt. It is definitely very painful to fix old bugs n dirty code that we may have done to quickly meet a deadline and those quick fixes ,some cases we may have to rewrite most of the application/code. No arguments about that. Some of the developers i had come across argued that they were already at the evolved stage where their coding doesn't need improvement or cant get improved anymore. Does this happen? If so how many years into coding on a particular language does one expect this to happen?

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  • Is the "One Description Table to rule them all" approch good?

    - by DavRob60
    Long ago, I worked (as a client) with a software which use a centralized table for it's codified element. Here, as far as I remember, how the table look like : Table_Name (PK) Field_Name (PK) Code (PK) Sort_Order Description So, instead of creating a table every time they need a codified field, they where just adding row in this table with the new Table_Name and Field_Name. I'm sometime tempted to use this pattern in some database I design, but I have resisted to this as from now, I think there's something wrong with this, but I cannot put the finger on it. It is just because you land with some of the structure logic within the Data or something else?

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  • Getting graduates up to speed?

    - by Simon
    This question got me thinking about how comapnies deal with newly-hired graduated. Do experienced programmers expect CS graduates to write clean code (by clean I mean code easily understandable by others — maybe that is too much to expect?) Or do significant portion of graduates at your place (if any) just end up testing and fixing small bugs on existing applications? And, even if they do bug fixes, do you end up spending double the amount of time just checking they did not end up breaking anything and creating new bugs? How do you deal with such scenarios when pair programming and code reviews are not available options (for reasons such as personal deadlines), and also what techniques did you find to get fresh graduate up to speed? Some suggestions would be great.

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  • What is the career path for a software developer/ programmer? [closed]

    - by Lo Wai Lun
    I've been working as a programmer for a few months and I often study CCNA , CISSP for future. Besides simple coding I was working on specs, designing applications, and all those around-like things. My question is, I want to be a information / system security specialist. what's the career path I should be aiming for? Is it like working on code for the rest of my life? :) Restart my career from the network engineer ? Or do programmers make a good manager-position people ? I know it's very subjective. Thing is, lately I find myself much more into the designing/working on specs part of the development project then the coding itself. How do you see it? Would you like to go from development to information security? Would you like to work on a project with a manager that used to be a coder?

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  • Should I extract specific functionality into a function and why?

    - by john smith optional
    I have a large method which does 3 tasks, each of them can be extracted into a separate function. If I'll make an additional functions for each of that tasks, will it make my code better or worse and why? Edit: Obviously, it'll make less lines of code in the main function, but there'll be additional function declarations, so my class will have additional methods, which I believe isn't good, because it'll make the class more complex. Edit2: Should I do that before I wrote all the code or should I leave it until everything is done and then extract functions?

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  • Should all, none, or some overriden methods call Super?

    - by JoJo
    When designing a class, how do you decide when all overridden methods should call super or when none of the overridden methods should call super? Also, is it considered bad practice if your code logic requires a mixture of supered and non-supered methods like the Javascript example below? ChildClass = new Class.create(ParentClass, { /** * @Override */ initialize: function($super) { $super(); this.foo = 99; }, /** * @Override */ methodOne: function($super) { $super(); this.foo++; }, /** * @Override */ methodTwo: function($super) { this.foo--; } }); After delving into the iPhone and Android SDKs, I noticed that super must be called on every overridden method, or else the program will crash because something wouldn't get initialized. When deriving from a template/delegate, none of the methods are supered (obviously). So what exactly are these "je ne sais quoi" qualities that determine whether a all, none, or some overriden methods should call super?

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