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• Profiling and containing memory per system

  - by chadb

  I have been interesting in profiling and keeping a managed memory pool for each subsystem, so I could get statistic on how much memory was being used in something such as sounds or graphics. However, what is the best design for doing this? I was thinking of using multiple allocators and just using one per subsystem, however, that would result in global variables for my allocators (or so it would seem to me). Another approach I have seen/been suggested is to just overload new and pass in an allocator for a parameter. I had a similar question over on stackoverflow here with a bounty, however, it seems as if perhaps I was too vague or just there is not enough people with knowledge in the subject.

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• Catching typos or other errors in web-based scripting languages

  - by foreyez

  Hi, My background is mainly strongly typed languages (java, c++, c#). Having recently gotten back to a bit of javascript, I found it a bit annoying that if I misspell something by accident (for example I'll type 'myvar' instead of 'myVar') my entire script crashes. The browser itself most of the time doesn't even tell me I have an error, my program will just be blank, etc. Then I have to hunt down my code line by line and find the error which is very time consuming. In the languages I am used to the compiler lets me know if I made a typo. My question to you is, how do you overcome this issue in scripting (javascript)? Can you give me some tips? (this question is mainly aimed at people that have also come from a strongly typed language). Note: I mainly use the terminal/VIM ... this is mainly b/c I like terminal and I SSH alot too

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• Query something and return the reason if nothing has been found

  - by Daniel Hilgarth

  Assume I have a Query - as in CQS that is supposed to return a single value. Let's assume that the case that no value is found is not exceptional, so no exception will be thrown in this case. Instead, null is returned. However, if no value has been found, I need to act according to the reason why no value has been found. Assuming that the Query knows the reason, how would I communicate it to the caller of the Query? A simple solution would be not return the value directly but a container object that contains the value and the reason: public class QueryResult { public TValue Value { get; private set; } public TReason ReasonForNoValue { get; private set; } } But that feels clumsy, because if a value is found, ReasonForNoValue makes no sense and if no value has been found, Value makes no sense. What other options do I have to communicate the reason? What do you think of one event per reason? For reference: This is going to be implemented in C#.

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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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• 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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• Test driven development - convince me!

  - by Casebash

  I know some people are massive proponents of test driven development. I have used unit tests in the past, but only to test operations that can be tested easily or which I believe will quite possibly be correct. Complete or near complete code coverage sounds like it would take a lot of time. What projects do you use test-driven development for? Do you only use it for projects above a certain size? Should I be using it or not? Convince me!

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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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• How to get started in coding for JBoss

  - by Mister IT Guru

  I have an idea on how to revamp our internal application, after having accessed the needs of the users, addressing thier current issues, and the like. But I am not a coder. My last application I wrote was in college, in C, (java wasn't invented-ish!) and it was a booking system, with the option to add on other modules, blah blah. I got an A, but I became a system administrator instead, more intrested in designing and maintainend networks and infrastructure, but with the advent of virtualisation, and linux management tools such as puppet I can now manage infrastructure in my sleep! Now I want to write code - to put on my infastructure, and I want to build .... a booking system! This is just to get experience, but I am at a loss as to where to start. Setting up the environment, will take me about a day. Writing the spec, even how I want it to work, I already know, but as for actually coding in a decent manner, I can only guess. If anyone can recommend a book, website, blog, twitter person to follow, or just advice on how to build a kick butt basic jboss app, then please, "I AM READY TO LEARN" :)

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• Is it bad practice 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 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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• would a composite design pattern be useful for group membership?

  - by changokun

  I'm trying to think about the best way to handle group memberships on a website. People sign up and select checkboxes in a list of interests. Every week we send out interest-themed emails to those members that indicated that interest. however i store the information in the database, while i am working with the lists and generating lists of email addresses or manipulating group memberships, the composite design pattern looked interesting. it would be easy to populate the group, then do some aggregating functions that say... generate the list of email addresses based on the interests. but i'm not sure i'm seeing any other advantages. i do need something scalable, and flexible. thoughts?

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• What is the best approach to solve a factory method problem which has to be an instance?

  - by Iago

  I have to add new funcionality in a web service legacy project and I'm thinking what is the best approach for a concrete situation. The web service is simple: It receives a XML file, unmarshalling, generates response's objects, marshalling and finally it sends the response as a XML file. For every XML files received, the web service always responds with the same XML structure. What I have to do is to generate a different XML file according to the XML received. So I have a controller class which has all marshalling/unmarshalling operations, but this controller class has to be an instance. Depending on XML received I need some marshalling methods or others. Trying to make few changes on legacy source, what is the best approach? My first approach was to do a factory method pattern with the controller class, but this class has to be an instance. I want to keep, as far as it goes, this structure: classController.doMarshalling(); I think this one is a bit smelly: if(XMLReceived.isTypeOne()) classController.doMarshallingOne(); else if(XMLReceived.isTypeTwo()) classController.doMarshallingTwo(); else if(XMLReceived.isTypeThree()) classController.doMarshallingThree(); else if ... I hope my question is well understood

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• Passing data between engine layers

  - by spaceOwl

  I am building a software system (game engine with networking support ) that is made up of (roughly) these layers: Game Layer Messaging Layer Networking Layer Game related data is passed to the messaging layer (this could be anything that is game specific), where they are to be converted to network specific messages (which are then serialized to byte arrays). I'm looking for a way to be able to convert "game" data into "network" data, such that no strong coupling between these layers will exist. As it looks now, the Messaging layer sits between both layers (game and network) and "knows" both of them (it contains Converter objects that know how to translate between data objects of both layers back and forth). I am not sure this is the best solution. Is there a good design for passing objects between layers? I'd like to learn more about the different options.

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• Object oriented wrapper around a dll

  - by Tom Davies

  So, I'm writing a C# managed wrapper around a native dll. The dll contains several hundred functions. In most cases, the first argument to each function is an opaque handle to a type internal to the dll. So, an obvious starting point for defining some classes in the wrapper would be to define classes corresponding to each of these opaque types, with each instance holding and managing the opaque handle (passed to its constructor) Things are a little awkward when dealing with callbacks from the dll. Naturally, the callback handlers in my wrapper have to be static, but the callbacks arguments invariable contain an opaque handle. In order to get from the static callback back to an object instance, I've created a static dictionary in each class, associating handles with class instances. In the constructor of each class, an entry is put into the dictionary, and this entry is then removed in the Destructors. When I receive a callback, I can then consult the dictionary to retrieve the class instance corresponding to the opaque reference. Are there any obvious flaws to this? Something that seems to be a problem is that the existence static dictionary means that the garbage collector will not act on my class instances that are otherwise unreachable. As they are never garbage collected, they never get removed from the dictionary, so the dictionary grows. It seems I might have to manually dispose of my objects, which is something absolutely would like to avoid. Can anyone suggest a good design that allows me to avoid having to do this?

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• A solution for a PHP website without a framework

  - by lortabac

  One of our customers asked us to add some dynamic functionality to an existent website, made of several static HTML pages. We normally work with an MVC framework (mostly CodeIgniter), but in this case moving everything to a framework would require too much time. Since it is not a big project, not having the full functionality of a framework is not a problem. But the question is how to keep code clean. The solution I came up with is to divide code in libraries (the application's API) and models. So inside HTML there will only be API calls, and readability will not be sacrificed. I implemented this with a sort of static Registry (sorry if I'm wrong, I am not a design pattern expert): <?php class Custom_framework { //Global database instance private static $db; //Registered models private static $models = array(); //Registered libraries private static $libraries = array(); //Returns a database class instance static public function get_db(){ if(isset(self::$db)){ //If instance exists, returns it return self::$db; } else { //If instance doesn't exists, creates it self::$db = new DB; return self::$db; } } //Returns a model instance static public function get_model($model_name){ if(isset(self::$models[$model_name])){ //If instance exists, returns it return self::$models[$model_name]; } else { //If instance doesn't exists, creates it if(is_file(ROOT_DIR . 'application/models/' . $model_name . '.php')){ include_once ROOT_DIR . 'application/models/' . $model_name . '.php'; self::$models[$model_name] = new $model_name; return self::$models[$model_name]; } else { return FALSE; } } } //Returns a library instance static public function get_library($library_name){ if(isset(self::$libraries[$library_name])){ //If instance exists, returns it return self::$libraries[$library_name]; } else { //If instance doesn't exists, creates it if(is_file(ROOT_DIR . 'application/libraries/' . $library_name . '.php')){ include_once ROOT_DIR . 'application/libraries/' . $library_name . '.php'; self::$libraries[$library_name] = new $library_name; return self::$libraries[$library_name]; } else { return FALSE; } } } } Inside HTML, API methods are accessed like this: <?php echo Custom_framework::get_library('My_library')->my_method(); ?> It looks to me as a practical solution. But I wonder what its drawbacks are, and what the possible alternatives.

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• Should all, none, or some overridden 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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• Should a primary key be immutable?

  - by Vincent Malgrat

  A recent question on stackoverflow provoked a discussion about the immutability of primary keys. I had thought that it was a kind of rule that primary keys should be immutable. If there is a chance that some day a primary key would be updated, I thought you should use a surrogate key. However it is not in the SQL standard and some RDBMS' "cascade update" feature allows a primary key to change. So my question is: is it still a bad practice to have a primary key that may change ? What are the cons, if any, of having a mutable primary key ?

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• What do you think about RefactoringManifesto.org?

  - by Gan

  Quite some time ago, on December 19 2010, a site called RefactoringManifesto.org was launched. The site is to voice concerns about refactoring. It lists ten main points as shown below (head over the website to see more details): Make your products live longer! Design should be simple so that it is easy to refactor. Refactoring is not rewriting. What doesn't kill it makes it stronger. Refactoring is a creative challenge. Refactoring survives fashion. To refactor is to discover. Refactoring is about independence. You can refactor anything, even total crap. Refactor – even in bad times! What do you think about this? Would you sign the manifesto? If not, why?

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• How can i manage my personal notes , code snippets files in one place online [closed]

  - by user1758043

  Whenever i work on any project , then i have so much notes , diagrams files , image s, brainstorming ideas which i want to keep. i want to put them in one place so that i can see the history of my work. Is there any toll whichere i can store this online. my company is using confluence but thats costly for me. I want something for single user but online in clou where i can store Notes Code snippets Diagrams , flowchart Attah files , images Books marks , sites

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• How to store prices that have effective dates?

  - by lal00

  I have a list of products. Each of them is offered by N providers. Each providers quotes us a price for a specific date. That price is effective until that provider decides to set a new price. In that case, the provider will give the new price with a new date. The MySQL table header currently looks like: provider_id, product_id, price, date_price_effective Every other day, we compile a list of products/prices that are effective for the current day. For each product, the list contains a sorted list of the providers that have that particular product. In that way, we can order certain products from whoever happens to offer the best price. To get the effective prices, I have a SQL statement that returns all rows that have date_price_effective >= NOW(). That result set is processed with a ruby script that does the sorting and filtering necessary to obtain a file that looks like this: product_id_1,provider_1,provider_3,provider8,provider_10... product_id_2,provider_3,provider_2,provider1,provider_10... This works fine for our purposes, but I still have an itch that a SQL table is probably not the best way to store this kind of information. I have that feeling that this kind of problema has been solved previously in other more creative ways. Is there a better way to store this information other than in SQL? or, if using SQL, is there a better approach than the one I'm using?

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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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• 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 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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• How do you keep track of the authors of code?

  - by dustyprogrammer

  This is something I was never taught. I have seen alot of different types of authoring styles. I code primarily in Java and Python. I was wondering if there was a standard authoring style or if everything is freestyle. Also if you answer would you mind attaching the style you use to author files that your create at home or at work. I usually just go @author garbagecollector @company garbage inc.

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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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