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  • Generalized plugable caching pattern?

    - by BCS
    Given that it's one of the hard things in computer science, does anyone know of a way to set up a plugable caching strategy? What I'm thinking of would allow me to write a program with minimal thought as to what needs to be cached (e.i. use some sort of boiler-plate, low/no cost pattern that compiles away to nothing anywhere I might want caching) and then when things are further along and I know where I need caching I can add it in without making invasive code changes. As an idea to the kind of solution I'm looking for; I'm working with the D programing language (but halfway sane C++ would be fine) and I like template.

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  • Separation of interfaces and implementation

    - by bonefisher
    From assembly(or module) perspective, what do you think of separation of Interface (1.assembly) and its Implementation (2.assembly)? In this way we can use some IoC container to develop more decoupling desing.. Say we have an assembly 'A', which contains interfaces only. Then we have an assembly 'B' which references 'A' and implements those interfaces..It is dependent only on 'A'. In assembly 'C' then we can use the IoC container to create objects of 'A' using dependency injection of objects from 'B'. This way 'B' and 'C' are completely unaware (not dependent) of themselves..

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  • How to solve the problem of not being informed of successful payments by the 3rd party system used b

    - by user68759
    I have a subscription based website that interacts with a 3rd party system to handle the payments. The steps to process a new subscriber registration are as follow: The subscriber enters his/her details in the subscription form and click on the submit button. Assuming the details specified are valid, a new record is created in the database to store these details. The subscriber is then redirected to the website of the 3rd party system (similar to paypal) to process the payment. Once the payment is succesful, the 3rd party website then redirect the subscriber back to our website. At this time, I know that the payment was succesful, so the record in the database is updated to indicate that payment has been made successfully. A problem that I have found occurring quite often is that if a subscriber pays but does not complete the process correctly (e.g. uses the back browser, closes the window), his/her record in the database doesn't get updated about this. Accordingly, I don't know if s/he has paid by just looking the record and need to wait for the report from the 3rd party system to find this out. How do you solve this problem? PS. One of the main reasons to store their details into the database before the payment process is done is so they can come back to complete the payment without re-entering their details again. For example, when their credit cards were rejected by the 3rd party system and they need to sort this out with their financial institution which may take a while.

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  • Is it good practice to generally make heavyweight classes non-copyable?

    - by Emile Cormier
    I have a Shape class containing potentially many vertices, and I was contemplating making copy-constructor/copy-assignment private to prevent accidental needless copying of my heavyweight class (for example, passing by value instead of by reference). To make a copy of Shape, one would have to deliberately call a "clone" or "duplicate" method. Is this good practice? I wonder why STL containers don't use this approach, as I rarely want to pass them by value.

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  • What problems do you find with this view on domain-driven design?

    - by Bozho
    I just wrote a long (and messy) blogpost about my view on domain-driven design at present day, with frameworks like spring and hibernate massively in use. I'd ask you to spot any problems with my views on the matter - why this won't work, why it isn't giving the benefits of DDD, why it is not a good idea in general. The blogpost is here (I don't think I need to copy-paste it on SO - if you think I should, tell me). I know the question is subjective, but it is aimed at gathering the most predominant opinions. (I'm tagging Java, since the frameworks discussed are Java frameworks)

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  • DRYing up Rails Views with Nested Resources

    - by viatropos
    What is your solution to the problem if you have a model that is both not-nested and nested, such as products: a "Product" can belong_to say an "Event", and a Product can also just be independent. This means I can have routes like this: map.resources :products # /products map.resources :events do |event| event.resources :products # /events/1/products end How do you handle that in your views properly? Note: this is for an admin panel. I want to be able to have a "Create Event" page, with a side panel for creating tickets (Product), forms, and checking who's rsvp'd. So you'd click on the "Event Tickets" side panel button, and it'd take you to /events/my-new-event/tickets. But there's also a root "Products" tab for the admin panel, which could list tickets and other random products. The 'tickets' and 'products' views look 90% the same, but the tickets will have some info about the event it belongs to. It seems like I'd have to have views like this: products/index.haml products/show.haml events/products/index.haml events/products/show.haml But that doesn't seem DRY. Or I could have conditionals checking to see if the product had an Event (@product.event.nil?), but then the views would be hard to understand. How do you deal with these situations? Thanks so much.

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  • Most efficient way to save tile data of an isometric game

    - by Harmen
    Hello, I'm working on an isometric game for fast browsers that support <canvas>, which is great fun. To save information of each tile, I use a two-dimensional array which contains numbers representing a tile ID, like: var level = [[1, 1, 1, 2, 1, 0], [0, 1, 1, 2, 0, 1], [0, 1, 1, 2, 1, 1]]; var tiles = [ {name: 'grass', color: 'green'}, {name: 'water', color: 'blue'}, {name: 'forest', color: 'ForestGreen'} ]; So far it works great, but now I want to work with heights and slopes like in this picture: For each tile I need to save it's tile ID, height and information about which corners are turned upward. I came up with a simple idea about a bitwise representation of all four corners, like this: 1011 // top, bottom and left corner turned up My question is: what is the most efficient way to save these three values for each cell? Is it possible to save these three values as one integer?

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  • Guidelines for good webcrawler 'Etiquette'

    - by Harry
    I'm building a search engine (for fun) and it has just struck me that potentially my little project might wreak havok by clicking on ads and all sorts of problems. So what are the guidelines for good webcrawler 'Etiquette'? Things that spring to mind: Observe Robot.txt instructions Limit the number of simultaneous requests to the same domain Don't follow ad links? Stopping the crawler from clicking on ads - This one is particularly on my mind at the moment... how do i stop my bot from 'clicking' on ads? if it is going straight to the url in the ad is it counted as a click?

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  • What ways are there for cleaning an R environment from objects?

    - by Tal Galili
    I know I can use ls() and rm() to see and remove objects that exist in my environment. However, when dealing with "old" .RData file, one needs to sometimes pick an environment a part to find what to keep and what to leave out. What I would like to do, is to have a GUI like interface to allow me to see the objects, sort them (for example, by there size), and remove the ones I don't need (for example, by a check-box interface). Since I imagine such a system is not currently implemented in R, what ways do exist? What do you use for cleaning old .RData files? Thanks, Tal

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  • Passing arguments and values from HTML to jQuery (events)

    - by Jaroslav Moravec
    What is the practice to pass arguments from HTML to jQuery events function. For example getting id of row from db: <tr class="jq_killMe" id="thisItemId-id"> ... </tr> and jQuery: $(".jq_killMe").click(function () { var tmp = $(this).attr('id).split("-"); var id = tmp[0] // ... } What's the best practise, if I want to pass more than one argument? Is it better not to use jQuery? For example: <tr onclick="killMe('id')"> ... </tr> I didn't find the answer on my question, I will be glad even for links. Thanks. Edit (pre solution) So you suggested two methods to do that: Add custom attributes to element (XHTML) Use attribute ID and parse it by regex Attribute data-* attributes in HTML5 Use hidden children elements I like first solution, but... I would like to (I have to (employer)) produce valid code. Here is a nice question and answers: http://stackoverflow.com/questions/994856/so-what-if-custom-html-attributes-arent-valid-xhtml And the second is not so pretty as the first, but valid. So the compromise is... The third is the solution for future, but here is a lot of CMS where we have to use XHTML or HTML4. (And HTML5 is the long process)

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  • Reverse search in Hibernate Search

    - by Javi
    Hello, I'm using Hibernate Search (which uses Lucene) for searching some Data I have indexed in a directory. It works fine but I need to do a reverse search. By reverse search I mean that I have a list of queries stored in my database I need to check which one of these queries match with a Data object each time Data Object is created. I need it to alert the user when a Data Object matches with a Query he has created. So I need to index this single Data Object which has just been created and see which queries of my list has this object as a result. I've seen Lucene MemoryIndex Class to create an index in memory so I can do something like this example for every query in a list (though iterating in a Java list of queries would not be very efficient): //Iterating over my list<Query> MemoryIndex index = new MemoryIndex(); //Add all fields index.addField("myField", "myFieldData", analyzer); ... QueryParser parser = new QueryParser("myField", analyzer); float score = index.search(query); if (score > 0.0f) { System.out.println("it's a match"); } else { System.out.println("no match found"); } The problem here is that this Data Class has several Hibernate Search Annotations @Field,@IndexedEmbedded,... which indicated how fields should be indexed, so when I invoke index() method on the FullTextEntityManager instance it uses this information to index the object in the directory. Is there a similar way to index it in memory using this information? Is there a more efficient way of doing this reverse search? Thanks

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  • Choosing between instance methods and separate functions?

    - by StackedCrooked
    Adding functionality to a class can be done by adding a method or by defining a function that takes an object as its first parameter. Most programmers that I know would choose for the solution of adding a instance method. However, I sometimes prefer to create a separate function. For example, in the example code below Area and Diagonal are defined as separate functions instead of methods. I find it better this way because I think these functions provide enhancements rather than core functionality. Is this considered a good/bad practice? If the answer is "it depends", then what are the rules for deciding between adding method or defining a separate function? class Rect { public: Rect(int x, int y, int w, int h) : mX(x), mY(y), mWidth(w), mHeight(h) { } int x() const { return mX; } int y() const { return mY; } int width() const { return mWidth; } int height() const { return mHeight; } private: int mX, mY, mWidth, mHeight; }; int Area(const Rect & inRect) { return inRect.width() * inRect.height(); } float Diagonal(const Rect & inRect) { return std::sqrt(std::pow(static_cast<float>(inRect.width()), 2) + std::pow(static_cast<float>(inRect.height()), 2)); }

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  • Parent child class relationship design pattern

    - by Jeremy
    I have a class which has a list of child items. Is there a design pattern I can copy that I can apply to these classes so that I can access the parent instance from the child, and it enforces rules such as not being able to add the child to multiple parents, etc?

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  • What design pattern shall I use in this question?

    - by iyad al aqel
    To be frank, this is a homework question, so I'll tell you my opinion. Can you let me know my mistakes rather than giving me the solution? This is the question : Assume a restaurant that only offers the following two types of meals: (a) a full meal and (b)an economic meal. The full meal consists of the following food items and is served in the following order: 1. Appetizer 2. Drink 3. Main dish 4. Dessert Meanwhile the economic meal consists of the following food items and is served in the following order: 1. Drink 2. Main dish Identify the most appropriate design pattern that can be used to allow a customer to only order using one of the two types of meals provided and that the meal components must be served in the given order. I'm confused between the Factory and the Iterator and using them both together. Using the factory Pattern we can create the two meals full and economic and provide the user with with a base object class that will decide upon. But how can we enforce the ordering of the elements, I thought of using the iterator along that will iterate through the the composite of the two created factories sort of speak. What do you think?

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  • Overriding properties of child view controller vs setting them via parent view controller

    - by robinjam
    If you want to modify the default behaviour of a View Controller by changing the value of one of its properties, is it considered better form to instantiate the class and set its property directly, or subclass it and override the property? With the former it would become the parent View Controller's responsibility to configure its children, whereas with the latter the children would effectively configure themselves. EDIT: Some more information: The class I am referring to is FetchedTableViewController, a subclass of UITableViewController that I made to display the results of a Core Data fetch operation. There are two places I want to display the results of a fetch, and they each have different fetch requests. I'm trying to decide whether it's better to create a subclass for each one, and override the fetchRequest property, or make it the responsibility of the parent controller to set the fetchRequest property for its children.

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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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  • Should non-English member names be changed to English?

    - by M.A. Hanin
    Situation: Automatically generated memebers, such as MenuStrip items, have their (automatically generated) names based on the text entered when the item was created. My most common situation is creating a menu-strip and adding menu-items by entering their text (using the graphical designer). Since my GUI is in Hebrew, all these members have a name which contains a Hebrew string. Something like "(hebrew-text)ToolStripItem". When I create event handlers, the event handlers "inherit" the hebrew text: "(hebrew-text)ToolStripMenuItem_Click". This actually works well, IntelliSense has no problem with Hebrew text, and so does the compiler. The question is: should I change these names (or prevent them from being created in the first place)? What are the possible consequences of keeping those names?

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  • Service Layer Patter - Could we avoid the service layer on a specific case?

    - by lidermin
    Hi, we are trying to implement an application using the Service Layer Pattern cause our application needs to connect to other multiple applications too, and googling on the web, we found this link of a demostrative graphic for the "right" way of apply the pattern: martinfowler.com - Service Layer Pattern But now we have a question: what if our system needs to implement some business logic, only for our application (like some maintenance data for the system itself) that we don't need to share with other systems. Based on this graphic: As it seems, it will be unnecesary to implement a service layer just for that; it will be more practical to avoid the service layer, and just go from User Interface to the Business Layer (for example). What should be the right way in this case to implement the Service Layer Pattern? What do you suggest us for a scenario like the one I told you? Thanks in advance.

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  • Service Layer Patter - Could we avoid the service layer on a specific case?

    - by lidermin
    Hi, we are trying to implement an application using the Service Layer Pattern cause our application needs to connect to other multiple applications too, and googling on the web, we found this link of a demostrative graphic for the "right" way of apply the pattern: martinfowler.com - Service Layer Pattern But now we have a question: what if our system needs to implement some business logic, only for our application (like some maintenance data for the system itself) that we don't need to share with other systems. Based on this graphic: As it seems, it will be unnecesary to implement a service layer just for that; it will be more practical to avoid the service layer, and just go from User Interface to the Business Layer (for example). What should be the right way in this case to implement the Service Layer Pattern? What do you suggest us for a scenario like the one I told you? Thanks in advance.

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  • Modular enterprise architecture using MVC and Orchard CMS

    - by MrJD
    I'm making a large scale MVC application using Orchard. And I'm going to be separating my logic into modules. I'm also trying to heavily decouple the application for maximum extensibility and testability. I have a rudimentary understanding of IoC, Repository Pattern, Unit of Work pattern and Service Layer pattern. I've made myself a diagram. I'm wondering if it is correct and if there is anything I have missed regarding an extensible application. Note that each module is a separate project.

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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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