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  • MVC pattern synchronisation

    - by Hariprasad
    I am facing a problem in synchronizing my model and view threads I have a view which is table. In it, user can select a few rows. I update the view as soon as the user clicks on any row since I don't want the UI to be slow. This updating is done by a logic which runs in the controller thread below. At the same time, the controller will update the model data too, which takes place in a different thread. i.e., controller puts the query in a queue, which is then executed by the model thread - which is a single-threaded interface. As soon as the query executes, controller will get a signal. Now, In order to keep the view and model synchronized, I will update the view again based on the return value of the query (the data returned by model) - even though I updated the view already for that user action. But, I am facing issues because, its taking a lot of time for the model to return the result, by that time user would have performed multiple clicks. So, as a result of updating the view again based on the information from model, the view sometimes goes back to the state in which the previous clicks were made (Suppose user clicks thrice on different rows. I update the view as soon as the click happens. Also, I update the view when I get data back from the model - which is supposed to be same as the already updated state of the view. Now, when the user clicks third time, I get data for the first click from model. As a result, view goes back to a state which is generated by the first click) Is there any way to handle such a synchronization issue?

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  • Necessary Infrastructure for large project with many components communicating through IPCs

    - by jluzwick
    I have a fairly in depth question which probably doesn't have an exact answer. As a software engineer, I am usually tasked with working on a program or project with minimal understanding of how other components or programs in the project interact with each other. When one program fails in a sea of multiple components and processes, what infrastructure elements are necessary to ensure that the problem can be accurately tracked to the violating application? More specifically, what infrastructure elements should be necessary for this large project and which are optional but very helpful. One such example I can think of is some form of a common logging infrastructure that allows for a developer or tester to easily browse through a log that contains numerous components for messages that might allude to the culprit program along with a "trail" of what happened before the issue occurred. I'm thinking of something similar to Androids alogcat tool. These necessary infrastructure elements should be language-agnostic. While these elements should be understood by all engineers on the team in question, which elements should be understood at great detail by the technical system engineers and what should the individual software engineers be responsible for adding to their tools to allow for such infrastructures to take hold? Please feel free to ask for clarification if something does not make sense as I understand this question is very broad and needs some refinement. I will refine as necessary from the answers and comments I receive. Thanks for any help!

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  • How do I create a game that runs on Windows, iOS and Android?

    - by AspaApps
    I use C++ to create windows games and now I want to step into another other OS like Android or iOS. I'm totally familiar with C++ so I tried to create app for iOS using objective C it was working awesome. However, I also want to publish games for Android but not by using Java. I don't want to create a single game 5-6 times for other platforms. Is their any way that if I create game for Windows then it will work in Android and iOS ? Or should I use Action Script 3.0? If I use action script 3.0, will it require Flash player to run the game in Windows, Android, iOS?

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  • Integrating with a payment provider; Proper and robust OOP approach

    - by ExternalUse
    History We are currently using a so called redirect model for our online payments (where you send the payer to a payment gateway, where he inputs his payment details - the gateway will then return him to a success/failure callback page). That's easy and straight-forward, but unfortunately quite inconvenient and at times confusing for our customers (leaving the site, changing their credit card details with an additional login on another site etc). Intention & Problem description We are now intending to switch to an integrated approach using an exchange of XML requests and responses. My problem is on how to cater with all (or rather most) of the things that may happen during processing - bearing in mind that normally simplicity is robust whereas complexity is fragile. Examples User abort: The user inputs Credit Card details and hits submit. An XML message to the provider's gateway is sent and waiting for response. The user hits "stop" in his browser or closes the window. ignore_user_abort() in PHP may be an option - but is that reliable? might it be better to redirect the user to a "please wait"-page, that in turn opens an AJAX or other request to the actual processor that does not rely on the connection? Database goes away sounds over-complicated, but with e.g. a webserver in the States and a DB in the UK, it has happened and will happen again: User clicks together his order, payment request has been sent to the provider but the response cannot be stored in the database. What approach could I use, using PHP to sort of start an SQL like "Transaction" that only at the very end gets committed or rolled back, depending on the individual steps? Should then neither commit or roll back have happened, I could sort of "lock" the user to prevent him from paying again or to improperly account for payments - but how? And what else do I need to consider technically? None of the integration examples of e.g. Worldpay, Realex or SagePay offer any insight, and neither Google or my search terms were good enough to find somebody else's thoughts on this. Thank you very much for any insight on how you would approach this!

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  • Progressbar patterns (Eclipse)

    - by JesperE
    I've struggled quite a bit with Eclipse and progress-monitors to try to have good progressbars which report useful progress information to the user. Inevitably the code gets cluttered with lots of things like if (monitor.isCancelled()) return; ... lengthyMethodCall(monitor.newChild(10)); and all over the place I need to pass a IProgressMonitor as an argument to my methods. This is bad, for several reasons: The code gets cluttered with lots of code which is not relevant to what the function actually does. I need to manually guesstimate which parts of the code takes time, and which parts do not. It interacts badly with automated tests; where much of the information which goes into a progressbar instead should be logged for later inspection. Is there a way out of this? Are there tools which can help me out with one or more of these problems? Should I be looking at Aspect-Oriented Programming tools, or are there other alternatives?

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  • Upgrading an app to support iOS5, 6 and 7

    - by drekka
    We are looking at an app that needs an upgrade. Currently it runs on iOS4, 5 & 6. The upgrade will move to iOS5, 6 & 7. It will also involve some UI changes and new features. I've been reading stuff on iOS7 and looking at things like auto-layout. What we are trying to figure out is the best way to handle the differences between the various iOS versions. Auto-layout seems like a good idea, but it's not available on iOS 5. There are also API changes to consider between all 3 versions and other new features of iOS7. So the questions: How would you handle auto layout given iOS5 does not have it? Are there any significant differences between the SDKs that you think would cause issues? Would we be better off with separate code bases?

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  • Service Layer - how broad should it be, and should it also be used from the local application?

    - by BornToCode
    The background: I need to build a desktop application with some operations (CRUD and more) (=winforms), I need to make another application which will re-use some of the functions of the main application (=webforms). I'm using service layer for reusing my functions. The service is calling the functions on the BL layer (correct me if I'm doing this wrong). so my desktop has 4 projects - DAL, BL, UI, WEBSERVICES. The dilemma (simple but I still need some more experienced opinions): In my main winform UI - should I call the functions from the BL - bl.getcustomers(), or do it similar to how I call it in the webform, and call the functions from the service - webservices.getcustomers? Should I create a service for every single function on the BL even if I need some of the functions only in one UI? for example - should I create services for all the CRUD operations, even though I need to re-use only update operation in the webform? YOUR HELP IS MUCH APPRECIATED

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  • find and replace app for ms word

    - by kittensatplay
    i program in python. i want to know if a program in python will work for ms word since ms word is not open source. the program basically changes words like ms word already does BUT it changes words based of off a list you write, which from what i know ms word doesnt do. if it does, just let me know. if there is a related program that is needed for a program in python or any language to work with a closed source software, jsut let me know.b also you can link to a phython specific place to ask phython related question if you know of one since im going to have a lot more in the future

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  • How does URL Rewriting affect SEO?

    - by Costa
    The following paragraph is from SEO Google Guide Google is good at crawling all types of URL structures, even if they're quite complex, but spending the time to make your URLs as simple as possible for both users and search engines can help. Some webmasters try to achieve this by rewriting their dynamic URLs to static ones; while Google is fine with this, we'd like to note that this is an advanced procedure and if done incorrectly, could cause crawling issues with your site. What makes URL re-writing implementation incorrect for GoogleBot? I am using Asp.net 3.5 framework.

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  • Creating a Application in Winrt that requires Internet

    - by wtsang02
    I am making a paid App for Windows 8, c#. I am wondering which is better? If my application doesn't need internet connection normally but does requires internet connection for the first time to download content data. --Makes my life easier Load the default data when installing. Then ask the user if he wants to update in app. -- Making the default data will be pain. Now my big question is, is it safe to assume user has access to internet now-a-days when using application that shouldn't require internet?

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  • correct pattern to handle a lot of entities in a game

    - by lezebulon
    In my game I usually have every NPC / items etc being derived from a base class "entity". Then they all basically have a virtual method called "update" that I would class for each entity in my game at every frame. I am assuming that this is a pattern that has a lot of downsides. What are some other ways to manage different "game objects" throughout the game? Are there other well-known patterns for this? My game is a RPG if that changes anything

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  • What options are there for splitting UI layout from code logic using a markup language?

    - by Daenyth
    What tools similar to GWT's UIBinder exist in other languages? By this I mean a system where you can define your UI layout in a markup language (preferably html+css) and attach the functionality to the layout using the code. I'm most interested in anything for python, but answers in other languages would interest me as well. I'm interested because the benefits of having a non-programmer work directly on the layout without needing to touch the code and adjust a bunch of UI toolkit method calls is very productive. I'm aware of Flex for flash, but is there anything else out there? What search terms might I use to find such frameworks? I've looked around but I haven't found anything concrete.

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  • returning null vs returning zero, which would be better?

    - by Dark Star1
    I inherited a project that I am managing and having to maintain pending the redevelopment of the code base. At the moment I am being tasked with adding little feature all over the place and have gotten into the habit of returning null instead of zero in parts of the code where I am working on. The problem is we have a client that is using this code and parts of code that require data from my implemented features recieve a null and dump the stack trace in UI. I would like to avoid this entirely from my input but without the nullPointer exceptions there's the potential that errors would be introduced into the client's data which may go un-noticed. Usually I would have come up with my own error notification system but I have never inherited a project before. so I am unsure whether to continue down this path. I still believe that the stack dump is preferable to un-noticed data corruption/inaccuracies.

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  • Finding the displacment of a robot [closed]

    - by Jordan Brown
    I'm building a quadruped (4 legs 3 DOF) for my major work in electronics at high school. I need to know the displacement of the robot and I can't use an encoding wheel. I've done my research and I found a system where I use an accelerometer, gyroscope and a magnetometer to determine the displacement but I'm not sure how to code it. I'm using Arduino and will use compatible sensors. I would like to be able to implement something similar to this video which demonstrates the principles evaluated in this paper. I don't need to map the data on a screen, just be able to read its displacement from its last recorded position. EG. (Read Position) --- (Do "stuff") --- (Read Position) --- (Calculate displacement caused by "stuff")

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  • How important is index size when searching?

    - by Michael K
    My company has recently began using Apache Solr to search its data. As we learn how to use it we have gone down the path of indexing multiple fields to get the results we need. Most of these are either N-Grammed or Edge-N-Grammed. Gramming by nature takes up a lot of space, which takes more time to search. Space is cheap, but time is less so. Index time is not too important, since a delta-import (only get the changes since last index) is extremely quick and you only pay a penalty on the first import. What we've not been able to determine is what effect the index size has on query times. Obviously a larger index takes longer to search, but the time added by n-gramming a field is difficult to predict. How do you determine whether a field is worth gramming? Can you predict how much longer a query will take when you gram a field?

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  • IoC containers and service locator pattern

    - by TheSilverBullet
    I am trying to get an understanding of Inversion of Control and the dos and donts of this. Of all the articles I read, there is one by Mark Seemann (which is widely linked to in SO) which strongly asks folks not to use the service locator pattern. Then somewhere along the way, I came across this article by Ken where he helps us build our own IoC. I noticed that is is nothing but an implementation of service locator pattern. Questions: Is my observation correct that this implementation is the service locator pattern? If the answer to 1. is yes, then Do all IoC containers (like Autofac) use the service locator pattern? If the answer to 1. is no, then why is this differen? Is there any other pattern (other than DI) for inversion of control?

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  • Anemic Domain Model, Business Logic and DataMapper (PHP)

    - by sunwukung
    I've implemented a rudimentary ORM layer based on DataMapper (I don't want to use a full blown ORM like Propel/Doctrine - for anything beyond simple fetch/save ops I prefer to access the data directly layer using a SQL abstraction layer). Following the DataMapper pattern, I've endeavoured to keep all persistence operations in the Mapper - including the location of related entities. My Entities have access to their Mapper, although I try not to call Mapper logic from the Entity interface (although this would be simple enough). The result is: // get a mapper and produce an entity $ProductMapper = $di->get('product_mapper'); $Product = $ProductMapper->find('[email protected]','email'); //.. mutaute some values.. save $ProductMapper->save($Product) // uses __get to trigger relation acquisition $Manufacturer = $Product->manufacturer; I've read some articles regarding the concept of an Anemic Domain model, i.e. a Model that does not contain any "business logic". When demonstrating the sort of business logic ideally suited to a Domain Model, however, acquiring related data items is a common example. Therefore I wanted to ask this question: Is persistence logic appropriate in Domain Model objects?

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  • Avoiding null in a controller

    - by Kevin Burke
    I'm trying to work through how to write this code. def get(params): """ Fetch a user's details, or 404 """ user = User.fetch_by_id(params['id']) if not user: abort(404) # Render some template for the user... What's the best way to handle the case where the lookup fails? One principle says you should avoid returning null values from functions. These lead to mistakes and AttributeErrors etc. later on in the file. Another idea is to have fetch_by_id raise a ValueError or similar if no user exists with that id. However there's a general principle that you shouldn't use exceptions for control flow, either, which doesn't help much. What could be done better in this case?

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  • How do you plan your asynchronous code?

    - by NullOrEmpty
    I created a library that is a invoker for a web service somewhere else. The library exposes asynchronous methods, since web service calls are a good candidate for that matter. At the beginning everything was just fine, I had methods with easy to understand operations in a CRUD fashion, since the library is a kind of repository. But then business logic started to become complex, and some of the procedures involves the chaining of many of these asynchronous operations, sometimes with different paths depending on the result value, etc.. etc.. Suddenly, everything is very messy, to stop the execution in a break point it is not very helpful, to find out what is going on or where in the process timeline have you stopped become a pain... Development becomes less quick, less agile, and to catch those bugs that happens once in a 1000 times becomes a hell. From the technical point, a repository that exposes asynchronous methods looked like a good idea, because some persistence layers could have delays, and you can use the async approach to do the most of your hardware. But from the functional point of view, things became very complex, and considering those procedures where a dozen of different calls were needed... I don't know the real value of the improvement. After read about TPL for a while, it looked like a good idea for managing tasks, but in the moment you have to combine them and start to reuse existing functionality, things become very messy. I have had a good experience using it for very concrete scenarios, but bad experience using them broadly. How do you work asynchronously? Do you use it always? Or just for long running processes? Thanks.

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  • Should one use a separate database for application data and user data?

    - by trycatch
    I’ve been working on a project for a little while and I’m unsure which is the better architecture. I’m interested in the consensus. The answer to me seems fairly obvious but something about it is digging at me and I can't pick out what. The TL;DR is: how do you handle a program with application data and user data in the same DB which needs to be able to receive updates to the application data periodically? One database for user data and one for application, or both in one? The detailed version is.. if an application has a database which needs to maintain application data AND user data, and the user data all references application data, it feels more natural to me to store them in the same database. But if there exists a need to be able to update the application data within this database periodically, should this be stripped into two databases so that one can simply download the updated application data database file as an update and replace the old one? Or should they remain as one database, and the application data be updated via a script which inserts the new data into the existing database? The second sounds clearly preferable to me... but for some reason just doesn’t feel right, and I can't pick out quite why.

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  • Why is x=x++ undefined?

    - by ugoren
    It's undefined because the it modifies x twice between sequence points. The standard says it's undefined, therefore it's undefined. That much I know. But why? My understanding is that forbidding this allows compilers to optimize better. This could have made sense when C was invented, but now seems like a weak argument. If we were to reinvent C today, would we do it this way, or can it be done better? Or maybe there's a deeper problem, that makes it hard to define consistent rules for such expressions, so it's best to forbid them? So suppose we were to reinvent C today. I'd like to suggest simple rules for expressions such as x=x++, which seem to me to work better than the existing rules. I'd like to get your opinion on the suggested rules compared to the existing ones, or other suggestions. Suggested Rules: Between sequence points, order of evaluation is unspecified. Side effects take place immediately. There's no undefined behavior involved. Expressions evaluate to this value or that, but surely won't format your hard disk (strangely, I've never seen an implementation where x=x++ formats the hard disk). Example Expressions x=x++ - Well defined, doesn't change x. First, x is incremented (immediately when x++ is evaluated), then it's old value is stored in x. x++ + ++x - Increments x twice, evaluates to 2*x+2. Though either side may be evaluated first, the result is either x + (x+2) (left side first) or (x+1) + (x+1) (right side first). x = x + (x=3) - Unspecified, x set to either x+3 or 6. If the right side is evaluated first, it's x+3. It's also possible that x=3 is evaluated first, so it's 3+3. In either case, the x=3 assignment happens immediately when x=3 is evaluated, so the value stored is overwritten by the other assignment. x+=(x=3) - Well defined, sets x to 6. You could argue that this is just shorthand for the expression above. But I'd say that += must be executed after x=3, and not in two parts (read x, evaluate x=3, add and store new value). What's the Advantage? Some comments raised this good point. It's not that I'm after the pleasure of using x=x++ in my code. It's a strange and misleading expression. What I want is to be able to understand complicated expressions. Normally, a complicated expression is no more than the sum of its parts. If you understand the parts and the operators combining them, you can understand the whole. C's current behavior seems to deviate from this principle. One assignment plus another assignment suddenly doesn't make two assignments. Today, when I look at x=x++, I can't say what it does. With my suggested rules, I can, by simply examining its components and their relations.

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  • Preferred way for dealing with customer-defined data in enterprise application

    - by Axarydax
    Let's say that we have a small enterprise web (intranet) application for managing data for car dealers. It has screens for managing customers, inventory, orders, warranties and workshops. This application is installed at 10 customer sites for different car dealers. First version of this application was created without any way to provide for customer-specific data. For example, if dealer A wanted to be able to attach a photo to a customer, dealer B wanted to add e-mail contact to each workshop, and dealer C wanted to attach multiple PDF reports to a warranty, each and every feature like this was added to the application, so all of the customers received everything on new update. However, this will inevitably lead to conflicts as the number of customers grow as their usage patterns are unique, and if, for instance, a specific dealer requested to have an ability to attach (for some reason) a color of inventory item (and be able to search by this color) as a required item, others really wouldn't need this feature, and definitely will not want it to be a required item. Or, one dealer would like to manage e-mail contacts for their employees on a separate screen of the application. I imagine that a solution for this is to use a kind of plugin system, where we would have a core of the application that provides for standard features like customers, inventory, etc, and all of the customer's installed plugins. There would be different kinds of plugins - standalone screens like e-mail contacts for employees, with their own logic, and customer plugin which would extend or decorate inventory items (like photo or color). Inventory (customer,order,...) plugins would require to have installation procedure, hooks for plugging into the item editor, item displayer, item filtering for searching, backup hook and such. Is this the right way to solve this problem?

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  • What are the advantages of storing xml in a relational database?

    - by Chris
    I was poking around the AdventureWorks database today and I noticed that a number of tables (HumanResources.JobCandidate and Sales.Individual for example) have a column which is storing xml data. What I would to know is, what is the advantage of storing basically a database table row's worth of data in another table's column? Doesn't this make it difficult to query off of this information? Or is the assumption that the data won't need to be queried and just needs to be stored?

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  • Dynamic Query Generation : suggestion for better approaches

    - by Gaurav Parmar
    I am currently designing a functionality in my Web Application where the verified user of the application can execute queries which he wishes to from the predefined set of queries with where clause varying as per user's choice. For example,Table ABC contains the following Template query called SecretReport "Select def as FOO, ghi as BAR from MNO where " SecretReport can have parameters XYZ, ILP. Again XYZ can have values as 1,2 and ILP can have 3,4 so if the user chooses ILP=3, he will get the result of the following query on his screen "Select def as FOO, ghi as BAR from MNO where ILP=3" Again the user is allowed permutations of XYZ / ILP My initial thought is that User will be shown a list of Report names and each report will have parameters and corresponding values. But this approach although technically simple does not appear intuitive. I would like to extend this functionality to a more generic level. Such that the user can choose a table and query based on his requirements. Of course we do not want the end user to take complete control of DB. But only tables and fields that are relevant to him. At present we are defining what is relevant in the code. But I want the Admin to take over this functionality such that he can decide what is relevant and expose the same to the user. On user's side it should be intuitive what is available to him and what queries he can form. Please share your thoughts what is the most user friendly way to provide this feature to the end user.

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  • Isn't class scope purely for organization?

    - by Di-0xide
    Isn't scope just a way to organize classes, preventing outside code from accessing certain things you don't want accessed? More specifically, is there any functional gain to having public, protected, or private-scoped methods? Is there any advantage to classifying method/property scope rather than to, say, just public-ize everything? My presumption says no simply because, in binary code, there is no sense of scope (other than r/w/e, which isn't really scope at all, but rather global permissions for a block of memory). Is this correct? What about in languages like Java and C#[.NET]?

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