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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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• 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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• Single Responsibility Principle: Responsibility unknown

  - by lurkerbelow

  I store sessions in a SessionManager. The session manager has a dependency to ISessionPersister. SessionManager private readonly ISessionPersister sessionPersister; public SessionManager(ISessionPersister sessionPersister) { this.sessionPersister = sessionPersister; } ISessionPersister public interface ISessionPersister : IDisposable { void PersistSessions(Dictionary<string, ISession> sessions); } Q: If my application shuts down how / where do I call PersistSessions? Who is responsible? First Approach: Use Dispose in SessionManager protected virtual void Dispose(bool disposing) { if (disposing) { if (this.sessionPersister != null && this.sessionMap != null && this.sessionMap.Count > 0) { this.sessionPersister.PersistSessions(this.sessionMap); } } } Is that the way to go or are there any better solutions?

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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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• How to solve cyclic dependencies in a visitor pattern

  - by Benjamin Rogge

  When programming at work we now and then face a problem with visitors and module/project dependencies. Say you have a class A in a module X. And there are subclasses B and C in module Y. That means that module Y is dependent on module X. If we want to implement a visitor pattern to the class hierarchy, thus introducing an interface with the handle Operations and an abstract accept method in A, we get a dependency from module Y to module X, which we cannot allow for architectural reasons. What we do is, use a direct comparison of the types (i.e. instanceof, since we program in Java), which is not satisfying. My question(s) would be: Do you encounter this kind of problem in your daily work (or do we make poor architectural choices) and if so, how is your approach to solve this?

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• Material System

  - by Towelie

  I'm designing Material/Shader System (target API DX10+ and may be OpenGL3+, now only DX10). I know, there was a lot of topics about this, but i can't find what i need. I don't want to do some kind of compilation/parsing scripts in real-time. So there some artist-created material, written at some analog of CG. After it compiled to hlsl code and after to final shader. Also there are some hard-coded ConstantBuffers, like cbuffer EveryFrameChanging { float4x4 matView; float time; float delta; } And shader use shared constant buffers to get parameters. For each mesh in the scene, getting needs and what it can give (normals, binormals etc.) and finding corresponding permutation of shader or calculating missing parts. Also, during build calculating render states and the permutations or hash for this shader which later will be used for sorting or even giving the ID from 0 to ShaderCount w/o gaps to it for sorting. FinalShader have only 1 technique and one pass. After it for each Mesh setting some shader and it's good to render. some pseudo code SetConstantBuffer(ConstantBuffer::PerFrame); foreach (shader in FinalShaders) SetConstantBuffer(ConstantBuffer::PerShader, shader); SetRenderState(shader); foreach (mesh in shader.GetAllMeshes) SetConstantBuffer(ConstantBuffer::PerMesh, mesh); SetBuffers(mesh); Draw(); class FinalShader { public: UUID m_ID; RenderState m_RenderState; CBufferBindings m_BufferBindings; } But i have no idea how to create this CG language and do i really need it?

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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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• 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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• Making a class pseudo-immutable by setting a flag

  - by scott_fakename

  I have a java project that involves building some pretty complex objects. There are quite a lot (dozens) of different ones and some of them have a HUGE number of parameters. They also need to be immutable. So I was thinking the builder pattern would work, but it ends up require a lot of boilerplate. Another potential solution I thought of was to make a mutable class, but give it a "frozen" flag, a-la ruby. Here is a simple example: public class EqualRule extends Rule { private boolean frozen; private int target; public EqualRule() { frozen = false; } public void setTarget(int i) { if (frozen) throw new IllegalStateException( "Can't change frozen rule."); target = i; } public int getTarget() { return target; } public void freeze() { frozen = true; } @Override public boolean checkRule(int i) { return (target == i); } } and "Rule" is just an abstract class that has an abstract "checkRule" method. This cuts way down on the number of objects I need to write, while also giving me an object that becomes immutable for all intents and purposes. This kind of act like the object was its own Builder... But not quite. I'm not too excited, however, about having an immutable being disguised as a bean however. So I had two questions: 1. Before I go too far down this path, are there any huge problems that anyone sees right off the bat? For what it's worth, it is planned that this behavior will be well documented... 2. If so, is there a better solution? Thanks

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• How can I cleanly and elegantly handle data and dependancies between classes

  - by Neophyte

  I'm working on 2d topdown game in SFML 2, and need to find an elegant way in which everything will work and fit together. Allow me to explain. I have a number of classes that inherit from an abstract base that provides a draw method and an update method to all the classes. In the game loop, I call update and then draw on each class, I imagine this is a pretty common approach. I have classes for tiles, collisions, the player and a resource manager that contains all the tiles/images/textures. Due to the way input works in SFML I decided to have each class handle input (if required) in its update call. Up until now I have been passing in dependencies as needed, for example, in the player class when a movement key is pressed, I call a method on the collision class to check if the position the player wants to move to will be a collision, and only move the player if there is no collision. This works fine for the most part, but I believe it can be done better, I'm just not sure how. I now have more complex things I need to implement, eg: a player is able to walk up to an object on the ground, press a key to pick it up/loot it and it will then show up in inventory. This means that a few things need to happen: Check if the player is in range of a lootable item on keypress, else do not proceed. Find the item. Update the sprite texture on the item from its default texture to a "looted" texture. Update the collision for the item: it might have changed shape or been removed completely. Inventory needs to be updated with the added item. How do I make everything communicate? With my current system I will end up with my classes going out of scope, and method calls to each other all over the place. I could tie up all the classes in one big manager and give each one a reference to the parent manager class, but this seems only slightly better. Any help/advice would be greatly appreciated! If anything is unclear, I'm happy to expand on things.

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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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• 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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• 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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• 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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• How to name multi-setter?

  - by IAdapter

  I'm struggling with how to name this method, I don't like the "set" prefix, because I feel it should be reserved for normal "dumb" setters and some tools might not like it (i did not check it in checkstyle, pmd, etc., but I got a feeling they won't like it.) for example (in java, but I feel its language agnostic) public void setField1Field2(String field1, String field2) { this.field1 = field1; this.field2 = field2; } The only purpose of this method is ONLY to set, this method is needed and cannot be joined with any other (because of framework used).

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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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• Tester/Doer pattern: Assume the caller conforms to the pattern or be defensive and repeat the check?

  - by Daniel Hilgarth

  Assume a simple class that implements the Tester/Doer pattern: public class FooCommandHandler : ICommandHandler { public bool CanHandle(object command) { return command is FooCommand; } public void Handle(object command) { var fooCommand = (FooCommand)command; // Do something with fooCommand } } Now, if someone doesn't conform to the pattern and calls Handle without verifying the command via CanHandle, the code in Handle throws an exception. However, depending on the actual implementation of Handle this can be a whole range of different exceptions. The following implementation would check CanHandle again in Handle and throw a descriptive exception: public void Handle(object command) { if(!CanHandle(command)) throw new TesterDoerPatternUsageViolationException("Please call CanHandle first"); // actual implementation of handling the command. } This has the advantage that the exception is very descriptive. It has the disadvantage that CanHandle is called twice for "good" clients. Is there a consensus on which variation should be used?

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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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• 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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• 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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• 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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• 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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• How should UI layer pass user input to BL layer?

  - by BornToCode

  I'm building an n-tier application, I have UI, BL, DAL & Entities (built from POCO) projects. (All projects have a reference to the Entities). My question is - how should I pass user input from the UI to the BL, as a bunch of strings passed to the BL method and the BL will build the object from the parameters, or should I build the objects inside the UI submit_function and send objects as parameters? EDIT: I wrote n-tier application, but what I actually meant was just layers.

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• Lag compensation with networked 2D games

  - by Milo

  I want to make a 2D game that is basically a physics driven sandbox / activity game. There is something I really do not understand though. From research, it seems like updates from the server should only be about every 100ms. I can see how this works for a player since they can just concurrently simulate physics and do lag compensation through interpolation. What I do not understand is how this works for updates from other players. If clients only get notified of player positions every 100ms, I do not see how that works because a lot can happen in 100ms. The player could have changed direction twice or so in that time. I was wondering if anyone would have some insight on this issue. Basically how does this work for shooting and stuff like that? Thanks

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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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