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  • Team activity/game for illustrating design in a SCRUM environment

    - by njreed.myopenid.com
    I'm looking for a team building / training activity for some of my scrum teams. I want something that really illustrates the flexibility that the team has when implementing stories to define the scope and complexity of the feature themselves. Most of the teams have long-term waterfall experience and are used to having a well-defined specification. I'm looking for something that illustrates the need for the team to vary the scope of what they are building themselves, dependent on the time and resources available. I couldn't find anything at tastycupcakes.com and Google wasn't much help. Maybe someone has prepared something themselves they would care to share?

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  • Proper Form Application Design

    - by Soo
    I'm creating a WinForm application in C# and one of its functions is displaying text in text boxes. I'm coding the logic for querying a database in a separate class and am unable to access the text box element in the class I'm creating (I'm getting a "name" does not exist in the current context error). Do I put all of my form logic into my Form1.cs file?

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  • Quick guide to Oracle IRM 11g: Server installation

    - by Simon Thorpe
    Quick guide to Oracle IRM 11g index This is the first of a set of articles designed to assist with the successful installation, configuration and deployment of a document security solution using Oracle IRM. This article goes through a set of simple instructions which detail how to download, install and configure the IRM server, the starting point for building a document security solution. This article contains a subset of information from the official documentation and is focused on installing the server on Oracle Enterprise Linux. If you are planning to deploy on a non-Linux platform, you will need to reference the documentation for platform specific information. Contents Introduction Downloading the software Preparing a database Creating the schema WebLogic Server installation Installing Oracle IRM Introduction Because we are using Oracle Enterprise Linux in this guide, and before we get into the detail of IRM, i'd like to share some tips with Linux to make life a bit easier.Use a 64bit platform, IRM 11g runs just fine on a 32bit server but with 64bit you will build a more future proof service. Download and install the latest Java JDK package. Make sure you get the 64bit version if you are on a 64bit server. Configure Linux to use a good Yum server to simplify installing packages. For Oracle Enterprise Linux we maintain a great public Yum here. Have at least 20GB of free disk space on the partition you intend to install the IRM server. The downloads are big, then you extract them and then install. This quickly consumes disk space which you can easily recover by deleting the downloaded and extracted files after wards. But it's nice to have the disk space spare to keep these around in case you need to restart any part of the installation process again. Downloading the software OK, so before you can do anything, you need the software install kits. Luckily Oracle allows you to freely download every technology we create. You'll need to get the following; Oracle WebLogic Server Oracle Database Oracle Repository Creation Utility (rcu) Oracle IRM server You can use Microsoft SQL server 2005 or 2008, in this guide i've used Oracle RDBMS 11gR2 for Linux. Preparing the database I'm not going to go through the finer points of installing the database. There are many very good guides on installing the Oracle Database. However one thing I would suggest you think about is enabling TDE, network encryption and using Database Vault. These Oracle database security technologies are excellent for creating a complete end to end security solution. No point in going to all the effort to secure document access with IRM when someone can go directly to the database and assign themselves rights to documents. To understand this further, you can see a video of the IRM service using these database security technologies here. With a database up and running we need to create a schema to hold the IRM data. This schema contains the rights model, cryptographic keys, user account id's and associated rights etc. Creating the IRM database schema Oracle uses the Repository Creation Tool which builds your schema, extract the files from the rcu zip. Then in a terminal window; cd /oracle/install/rcu/bin ./rcu This will launch the Repository Creation Tool and you will be presented with the image to the right. Hit next and continue onto the next dialog. You are asked if you are going to be creating a new schema or wish to drop an existing one, you obviously just need to click next at this point to create a new schema. The RCU next needs to know where your database is so you'll need the following details of your database instance. Below, for reference, is the information for my installation. Hostname: irm.oracle.demo Port: 1521 (This is the default TCP port for the Oracle Database) Service Name: irm.oracle.demo. Note this is not the SID, but the service name. Username: sys Password: ******** Role: SYSDBA And then select next. Because the RCU contains schemas for many of the Oracle Technologies, you now need to select to just deploy the Oracle IRM schema. Open the section under "Enterprise Content Management" and tick the "Oracle Information Rights Management" component. Note that you also get the chance to select a prefix which defaults to "DEV" (for development). I usually change this to something that reflects my own install. PROD for a production system, INT for internal only etc. The next step asks for the passwords for the schema users. We are only creating one schema here so you just enter one password. Some brave souls store this password in an Excel spreadsheet which is then secure against the IRM server you're about to install in this guide. Nearing the end of the schema creation is the mapping of the tablespaces to the schema. Note I had setup a table space already that was encrypted using TDE and at this point I was able to select that tablespace by clicking in the "Default Tablespace" column. The next dialog confirms your actions and clicking on next causes it to create the schema and default data. After this you are presented with the completion summary. WebLogic Server installation The database is now ready and the next step is to install the application server. Oracle IRM 11g is a JEE application and currently only supported in Oracle WebLogic Server. So the next step is get WebLogic Server installed, which is pretty easy. Depending on the version you download, you either run the binary or for a 64 bit platform (like mine) run the following command. java -d64 -jar wls1033_generic.jar And in the resulting dialog hit next to start walking through the install. Next choose a directory into which you will install WebLogic Server. I like to change from the default and install into /oracle/. Then all my software goes into this one folder, all owned by the "oracle" user. The next dialog asks for your Oracle support information to ensure you are kept up to date. If you have an Oracle support account, enter your details but for most evaluation systems I leave these fields blank. Again, for evaluation or development systems, I usually stick with the "Typical" install type which you are next asked for. Next you are asked for the JDK which will be used for the server. When installing from the generic jar on a 64bit platform like in this guide, no JDK is bundled with the installer. But as you can see in the image on the right, that it does a good job of detecting the one you've got installed. Defaults for the install directories are usually taken, no changes here, just click next. And finally we are ready to install, hit next, sit back and relax. Typically this takes about 10 minutes. After the install, do not run the quick start, we need to deploy the IRM install itself from which we will create a new WebLogic domain. For now just hit done and lets move to the final step of the installation process. Installing Oracle IRM The last piece of the puzzle to getting your environment ready is to deploy the IRM files themselves. Unzip the Oracle Enterprise Content Management 11g zip file and it will create a Disk1 directory. Switch to this folder and in the console run ./runInstaller. This will launch the installer which will also ask for the location of the JDK. Look at the image on the right for the detail. You should now see the first stage of the IRM installation. The dialog warns you need to have a WebLogic server installed and have created the schema's, but you've just done all that above (I hope) so we are ready to go. The installer now checks that you have all the required libraries installed and other system parameters are correct. Because nearly all of my development and evaluation installations have the database server on the same system, the installer passes these checks without issue... Next... Now chose where to install the IRM files, you must install into the same Middleware Home as the WebLogic Server installation you just performed. Usually the installer already defaults to this location anyway. I also tend to change the Oracle Home Directory to Oracle_IRM so it's clear this is just an IRM install. The summary page tells you about space needed to deploy the files. Unfortunately the IRM install comes with all of the other Oracle ECM software, you can't just select the IRM files, everything gets deployed to disk and uses 1.6GB of space! Not fun, but Oracle has to package up similar technologies otherwise we would have a very large number of installers to QA and manage, again, not fun. Hit Install, time for another drink, maybe a piece of cake or a donut... on a half decent system this part of the install took under 10 minutes. Finally the installation of your IRM server is complete, click on finish and the next phase is to create the WebLogic domain and start configuring your server. Now move onto the next article in this guide... configuring your IRM server ready to seal your first document.

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  • Data that has been deleted in P6, how is it updated in Analytics

    - by Jeffrey McDaniel
    In P6 Reporting Database 2.0 the ETL process looked to the refrdel table in the P6 PMDB to determine which projects were deleted. The refrdel table could not be cleared out between ETL runs or those deletes would be lost. After the ETL process is run the refrdel can be cleared out. It is important to keep any purging of the refrdel in a consistent cycle so the ETL process can pick up these deletes and process them accordingly.  In P6 Reporting Database 2.2 and higher the Extended Schema is used as the data source. In the Extended Schema, deleted data is filtered out by the views. The Extended Schema services will handle any interaction with the refrdel table, this concern with timing refrdel cleanup and ETL runs is not applicable as of this release. In the Extended Schema tables (ex. TaskX) there can still be deleted data present. The Extended Schema views join on the primary PMDB tables (ex. Task) and filter out any deleted data.  Any data that was deleted that remains in the Extended Schema tables can be cleaned out at a designated time by running the clean up procedure as documented in the P6 Extended Schema white paper. This can be run occasionally but is not necessary to run often unless large amounts of data has been deleted.

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  • Is a "model" branch a common practice?

    - by dukeofgaming
    I just thought it could be a good thing to have a dedicated version control branch for all database schema changes and I wanted to know if anyone else is doing the same and what have the results been. Say that you are working with: Schema model/documentation (some file where you model the database visually to generate the schema source, say MySQL Workbench, with a .mwb file, which is binary) Schema source (a .sql file) Schema-based code generation The normal way we were working was with feature branches, so we would do changes to the model files (the database specific ones), and then have to regenerate points 2 and 3, dealing with the possible conflicts (or even code rewriting). Now say that your workflow goes the same way as the previous item numbering. With a model branch you wouldn't have to reconcile the schema model with binaries in other feature branches, or have to regenerate schema source and regenerate code (which might have human code on top of it). It makes so much sense to me it feels weird not having seen this earlier as a common practice. Edit: I'm counting on branch merges to be the assertions for the model matching the code. I use a DVCS, so I don't fear long-lived branches or scary-looking merges. I'm also doing feature branching.

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  • Creating a Custom EventAggregator Class

    - by Phil
    One thing I noticed about Microsoft's Composite Application Guidance is that the EventAggregator class is a little inflexible. I say that because getting a particular event from the EventAggregator involves identifying the event by its type like so: _eventAggregator.GetEvent<MyEventType>(); But what if you want different events of the same type? For example, if a developer wants to add a new event to his application of type CompositePresentationEvent<int>, he would have to create a new class that derives from CompositePresentationEvent<int> in a shared library somewhere just to keep it separate from any other events of the same type. In a large application, that's a lot of little two-line classes like the following: public class StuffHappenedEvent : CompositePresentationEvent<int> {} public class OtherStuffHappenedEvent : CompositePresentationEvent<int> {} I don't really like that approach. It almost feels dirty to me, partially because I don't want a million two-line event classes sitting around in my infrastructure dll. What if I designed my own simple event aggregator that identified events by an event ID rather than the event type? For example, I could have an enum such as the following: public enum EventId { StuffHappened, OtherStuffHappened, YetMoreStuffHappened } And my new event aggregator class could use the EventId enum (or a more general object) as a key to identify events in the following way: _eventAggregator.GetEvent<CompositePresentationEvent<int>>(EventId.StuffHappened); _eventAggregator.GetEvent<CompositePresentationEvent<int>>(EventId.OtherStuffHappened); Is this good design for the long run? One thing I noticed is that this reduces type safety. In a large application, is this really as important of a concern as I think it is? Do you think there could be a better alternative design?

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  • Looking for a lock-free RT-safe single-reader single-writer structure

    - by moala
    Hi, I'm looking for a lock-free design conforming to these requisites: a single writer writes into a structure and a single reader reads from this structure (this structure exists already and is safe for simultaneous read/write) but at some time, the structure needs to be changed by the writer, which then initialises, switches and writes into a new structure (of the same type but with new content) and at the next time the reader reads, it switches to this new structure (if the writer multiply switches to a new lock-free structure, the reader discards these structures, ignoring their data). The structures must be reused, i.e. no heap memory allocation/free is allowed during write/read/switch operation, for RT purposes. I have currently implemented a ringbuffer containing multiple instances of these structures; but this implementation suffers from the fact that when the writer has used all the structures present in the ringbuffer, there is no more place to change from structure... But the rest of the ringbuffer contains some data which don't have to be read by the reader but can't be re-used by the writer. As a consequence, the ringbuffer does not fit this purpose. Any idea (name or pseudo-implementation) of a lock-free design? Thanks for having considered this problem.

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  • Moq and accessing called parameters

    - by lozzar
    I've just started to implement unit tests (using xUnit and Moq) on an already established project of mine. The project extensively uses dependency injection via the unity container. I have two services A and B. Service A is the one being tested in this case. Service A calls B and gives it a delegate to an internal function. This 'callback' is used to notify A when a message has been received that it must handle. Hence A calls (where b is an instance of service B): b.RegisterHandler(Guid id, Action<byte[]> messageHandler); In order to test service A, I need to be able to call messageHandler, as this is the only way it currently accepts messages. Can this be done using Moq? ie. Can I mock service B, such that when RegisterHandler is called, the value of messageHandler is passed out to my test? Or do I need to redesign this? Are there any design patterns I should be using in this case? Does anyone know of any good resources on this kind of design?

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  • What should be the responsibility of a presenter here?

    - by Achu
    I have a 3 layer design. (UI / BLL / DAL) UI = ASP.NET MVC In my view I have collection of products for a category. Example: Product 1, Product 2 etc.. A user able to select or remove (by selecting check box) product’s from the view, finally save as a collection when user submit these changes. With this 3 layer design how this product collection will be saved? How the filtering of products (removal and addition) to the category object? Here are my options. (A) It is the responsibility of the controller then the pseudo Code would be Find products that the user selected or removed and compare with existing records. Add or delete that collection to category object. Call SaveCategory(category); // BLL CALL Here the first 2 process steps occurs in the controller. (B) It is the responsibility of BLL then pseudo Code would be Collect products what ever user selected SaveCategory(category, products); // BLL CALL Here it's up to the SaveCategory (BLL) to decide what products should be removed and added to the database. Thanks

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  • How can I write good "research code"?

    - by John
    "Research code" is often held up as a paragon of what not to do when writing software. Certainly, the kind of code that often results from trying to solve a research problem can end up being poorly-designed, difficult to debug, etc. But my question is this: does research code have to be this way? Is it possible to write good research code? Is the only approach to consider the first version a poorly-written prototype to be discarded in favour of the better-designed second version? Software engineering has all sorts of best practices about how to design and write good code, but I don't usually find this relevant when you don't have a good idea ahead of time what the final system will look like. The final system is likely to be a result of what did or didn't work along the way, and the only way to determine what does or doesn't work is to write the code first. As you find things that don't work, you change what the final system looks like, moving further away from your original design (assuming you had one). I'd be interested in any personal experience with these issues, as well as any books or other resources anyone can point me to.

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  • Correctly use dependency injection

    - by Rune
    Me and two other colleagues are trying to understand how to best design a program. For example, I have an interface ISoda and multiple classes that implement that interface like Coke, Pepsi, DrPepper, etc.... My colleague is saying that it's best to put these items into a database like a key/value pair. For example: Key | Name -------------------------------------- Coke | my.namespace.Coke, MyAssembly Pepsi | my.namespace.Pepsi, MyAssembly DrPepper | my.namespace.DrPepper, MyAssembly ... then have XML configuration files that map the input to the correct key, query the database for the key, then create the object. I don't have any specific reasons, but I just feel that this is a bad design, but I don't know what to say or how to correctly argue against it. My second colleague is suggesting that we micro-manage each of these classes. So basically the input would go through a switch statement, something similiar to this: ISoda soda; switch (input) { case "Coke": soda = new Coke(); break; case "Pepsi": soda = new Pepsi(); break; case "DrPepper": soda = new DrPepper(); break; } This seems a little better to me, but I still think there is a better way to do it. I've been reading up on IoC containers the last few days and it seems like a good solution. However, I'm still very new to dependency injection and IoC containers, so I don't know how to correctly argue for it. Or maybe I'm the wrong one and there's a better way to do it? If so, can someone suggest a better method? What kind of arguments can I bring to the table to convince my colleagues to try another method? What are the pros/cons? Why should we do it one way? Unfortunately, my colleagues are very resistant to change so I'm trying to figure out how I can convince them.

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  • Programming tips for writing document editors?

    - by Tesserex
    I'm asking this because I'm in the process of writing two such editors for my Mega Man engine, one a tileset editor, and another a level editor. When I say document editor, I mean the superset application type for things like image editors and text editors. All of these share things like toolbars, menu options, and in the case of image editors, and my apps, tool panes. We all know there's tons of advice out there for interface design in these apps, but I'm wondering about programming advice. Specifically, I'm doubting my code designs with the following things: Many menu options toggle various behaviors. What's the proper way to reliably tie the checked state of the option with the status of the behavior? Sometimes it's more complicated, like options being disabled when there's no document loaded. More and more consensus seems to be against using MDI, but how should I control tool panes? For example, I can't figure out how to get the panels to minimize and maximize along with the main window, like Photoshop does. When tool panels are responsible for a particular part of the document, who actually owns that thing? The main window, or the panel class? How do you do communication between the tool panels and the main window? Currently mine is all event based but it seems like there could be a better way. This seems to be a common class of gui application, but I've never seen specific pointers on code design for them. Could you please offer whatever advice or experience you have for writing them?

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  • How to avoid game rendering component circular references?

    - by CodexArcanum
    I'm working on a simple game design, and I wanted to break up my game objects into more reusable components. But I'm getting stuck on how exactly to implement the design I have in mind. Here's an example: I have a Logger object, whose job is simply to store a list of messages and render them to screen. You know, logging. Originally the Logger just held the list, and the game loop rendered it's contents. Then I moved the rendering logic into the Logger.Draw() method, and now I want to move it further into a LoggerRenderer object. In effect, I want to have the game loop call RenderAll, which will then call Logger.Render, which will in turn call the LoggerRenderer.Render and finally output the text. So the Logger needs to contain a Renderer object, but the Renderer needs access to the Logger's state (the message queue) in order to render. How do I resolve that? Should I be passing in the message queue and other state information explicitly to the Render method? Or should the game loop be calling the Renderer directly and it links back to the logger, but the RenderAll method never actually sees the logger object itself? This feels kind of like Command pattern, but I'm botching it up terribly.

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  • What should every developer know about databases?

    - by Aaronaught
    Whether we like it or not, many if not most of us developers either regularly work with databases or may have to work with one someday. And considering the amount of misuse and abuse in the wild, and the volume of database-related questions that come up every day, it's fair to say that there are certain concepts that developers should know - even if they don't design or work with databases today. So: What are the important concepts that developers and other software professionals ought to know about databases? Guidelines for Responses: Keep your list short. One concept per answer is best. Be specific. "Data modelling" may be an important skill, but what does that mean precisely? Explain your rationale. Why is your concept important? Don't just say "use indexes." Don't fall into "best practices." Convince your audience to go learn more. Upvote answers you agree with. Read other people's answers first. One high-ranked answer is a more effective statement than two low-ranked ones. If you have more to add, either add a comment or reference the original. Don't downvote something just because it doesn't apply to you personally. We all work in different domains. The objective here is to provide direction for database novices to gain a well-founded, well-rounded understanding of database design and database-driven development, not to compete for the title of most-important.

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  • List of objects or parallel arrays of properties?

    - by Headcrab
    The question is, basically: what would be more preferable, both performance-wise and design-wise - to have a list of objects of a Python class or to have several lists of numerical properties? I am writing some sort of a scientific simulation which involves a rather large system of interacting particles. For simplicity, let's say we have a set of balls bouncing inside a box so each ball has a number of numerical properties, like x-y-z-coordinates, diameter, mass, velocity vector and so on. How to store the system better? Two major options I can think of are: to make a class "Ball" with those properties and some methods, then store a list of objects of the class, e. g. [b1, b2, b3, ...bn, ...], where for each bn we can access bn.x, bn.y, bn.mass and so on; to make an array of numbers for each property, then for each i-th "ball" we can access it's 'x' coordinate as xs[i], 'y' coordinate as ys[i], 'mass' as masses[i] and so on; To me it seems that the first option represents a better design. The second option looks somewhat uglier, but might be better in terms of performance, and it could be easier to use it with numpy and scipy, which I try to use as much as I can. I am still not sure if Python will be fast enough, so it may be necessary to rewrite it in C++ or something, after initial prototyping in Python. Would the choice of data representation be different for C/C++? What about a hybrid approach, e.g. Python with C++ extension?

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  • Modeling related objects and their templates

    - by Duddle
    Hello everybody! I am having trouble correctly modeling related objects that can use templates. This is not homework, but part of a small project in the university. In this application the user can add several elements, which can either be passive or active. Each concrete element has different attributes, these must be set by the user. See diagram 1: Since the user will create many elements, we want there to be templates for each type of element, so some of the attributes are filled in automatically. See diagram 2: In my opinion, this is a bad design. For example, to get all possible templates for a PassiveElementA-object, there has to be a list/set somewhere that only holds PassiveElementATemplate-objects. There has to be a separate list for each subclass of Element. So if you wanted to add a new PassiveElement-child, you also have to edit the class which holds all these separate lists. I cannot figure out a good way to solve this problem. Since the concrete classes (i.e. PassiveElementA, ..., PassiveElementZ) have so many different attributes, many of the design patterns I know do not work. Thanks in advance for any hints, and sorry for my bad English.

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  • What would you like to correct and/or improve in this java implementation of Chain Of Responsibility

    - by Maciek Kreft
    package design.pattern.behavioral; import design.pattern.behavioral.ChainOfResponsibility.*; public class ChainOfResponsibility { public static class Chain { private Request[] requests = null; private Handler[] handlers = null; public Chain(Handler[] handlers, Request[] requests){ this.handlers = handlers; this.requests = requests; } public void start() { for(Request r : requests) for (Handler h : handlers) if(h.handle(r)) break; } } public static class Request { private int value; public Request setValue(int value){ this.value = value; return this; } public int getValue() { return value; } } public static class Handler<T1> { private Lambda<T1> lambda = null; private Lambda<T1> command = null; public Handler(Lambda<T1> condition, Lambda<T1> command) { this.lambda = condition; this.command = command; } public boolean handle(T1 request) { if (lambda.lambda(request)) command.lambda(request); return lambda.lambda(request); } } public static abstract class Lambda<T1>{ public abstract Boolean lambda(T1 request); } } class TestChainOfResponsibility { public static void main(String[] args) { new TestChainOfResponsibility().test(); } private void test() { new Chain(new Handler[]{ // chain of responsibility new Handler<Request>( new Lambda<Request>(){ // command public Boolean lambda(Request condition) { return condition.getValue() >= 600; } }, new Lambda<Request>(){ public Boolean lambda(Request command) { System.out.println("You are rich: " + command.getValue() + " (id: " + command.hashCode() + ")"); return true; } } ), new Handler<Request>( new Lambda<Request>(){ public Boolean lambda(Request condition) { return condition.getValue() >= 100; } }, new Lambda<Request>(){ public Boolean lambda(Request command) { System.out.println("You are poor: " + command.getValue() + " (id: " + command.hashCode() + ")"); return true; } } ), }, new Request[]{ new Request().setValue(600), // chaining method new Request().setValue(100), } ).start(); } }

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  • Iterator performance contract (and use on non-collections)

    - by polygenelubricants
    If all that you're doing is a simple one-pass iteration (i.e. only hasNext() and next(), no remove()), are you guaranteed linear time performance and/or amortized constant cost per operation? Is this specified in the Iterator contract anywhere? Are there data structures/Java Collection which cannot be iterated in linear time? java.util.Scanner implements Iterator<String>. A Scanner is hardly a data structure (e.g. remove() makes absolutely no sense). Is this considered a design blunder? Is something like PrimeGenerator implements Iterator<Integer> considered bad design, or is this exactly what Iterator is for? (hasNext() always returns true, next() computes the next number on demand, remove() makes no sense). Similarly, would it have made sense for java.util.Random implements Iterator<Double>? Should a type really implement Iterator if it's effectively only using one-third of its API? (i.e. no remove(), always hasNext())

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  • Maintain List of Active Users for Web

    - by Bryan Marble
    Problem Statement - Would like to know if particular web app user is active (i.e. logged in and using site) and be able to query for list of active users or determine a user's activity status. Constraints - Doesn't need to be exact (i.e. if a user was active within a certain timeframe, that's ok to say that they're active even if they've closed their browser). I feel like there should be a design pattern for this type of problem but haven't been able to find anything here or elsewhere on the web. Approaches I'm considering: Maintain a table that is updated any time a user performs an action (or some subset of actions). Would then query for users that have performed an action within some threshold of time. Try to monitor session information and maintain a table that lists logged in users and times out after a certain period of time. Some other more standard way of doing this? How would you approach this problem (again, from a design pattern perspective)? Thanks!

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  • desing pattern for related inputs

    - by curiousMo
    My question is a design question : let's say i have a data entry web page with 4 drop down lists, each depending on the previous one, and a bunch of text boxes. country (ddl), state (ddl), city (ddl), boro (ddl), address (txtBox), zipcode(txtbox). and an object that represents a datarow with a value for each. naturally the country, state, city and boro values will be values of primary keys of some lookup tables. when the user chooses to edits that record, i would load it from database and load it into the page. the issue that I have is how to streamline loading the ddls. i have some code that would grab the object, look thru its values and move them to their corresponding input controls in one shot. but in this case i will have to load possible values of country, then assign values, then load values of state, then assign value ans so on. I guess i am looking for an elegant solution. i am using asp.net, but i think it is irrelevant to the question. i am looking more into a design pattern. thanks

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  • What do I name this class whose sole purpose is to report failure?

    - by Blair Holloway
    In our system, we have a number of classes whose construction must happen asynchronously. We wrap the construction process in another class that derives from an IConstructor class: class IConstructor { public: virtual void Update() = 0; virtual Status GetStatus() = 0; virtual int GetLastError() = 0; }; There's an issue with the design of the current system - the functions that create the IConstructor-derived classes are often doing additional work which can also fail. At that point, instead of getting a constructor which can be queried for an error, a NULL pointer is returned. Restructuring the code to avoid this is possible, but time-consuming. In the meantime, I decided to create a constructor class which we create and return in case of error, instead of a NULL pointer: class FailedConstructor : public IConstructor public: virtual void Update() {} virtual Status GetStatus() { return STATUS_ERROR; } virtual int GetLastError() { return m_errorCode; } private: int m_errorCode; }; All of the above this the setup for a mundane question: what do I name the FailedConstructor class? In our current system, FailedConstructor would indicate "a class which constructs an instance of Failed", not "a class which represents a failed attempt to construct another class". I feel like it should be named for one of the design patterns, like Proxy or Adapter, but I'm not sure which.

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  • What are some good ways to store performance statistics in a database for querying later?

    - by Nathan
    Goal: Store arbitrary performance statistics of stuff that you care about (how many customers are currently logged on, how many widgets are being processed, etc.) in a database so that you can understand what how your servers are doing over time. Assumptions: A database is already available, and you already know how to gather the information you want and are capable of putting it in the database however you like. Some Ideal Attributes of a Solution Causes no noticeable performance hit on the server being monitored Has a very high precision of measurement Does not store useless or redundant information Is easy to query (lends itself to gathering/displaying useful information) Lends itself to being graphed easily Is accurate Is elegant Primary Questions 1) What is a good design/method/scheme for triggering the storing of statistics? 2) What is a good database design for how to actually store the data? Example answers...that are sort of vague and lame... 1) I could, once per [fixed time interval], store a row of data with all the performance measurements I care about in each column of one big flat table indexed by timestamp and/or server. 2) I could have a daemon monitoring performance stuff I care about, and add a row whenever something changes (instead of at fixed time intervals) to a flat table as in #1. 3) I could trigger either as in #2, but I could store information about each aspect of performance that I'm measuring in separate tables, opening up the possibility of adding tons of rows for often-changing items, and few rows for seldom-changing items. Etc. In the end, I will implement something, even if it's some super-braindead approach I make up myself, but I'm betting there are some really smart people out there willing to share their experiences and bright ideas!

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  • When is a good time to start thinking about scaling?

    - by Slokun
    I've been designing a site over the past couple days, and been doing some research into different aspects of scaling a site horizontally. If things go as planned, in a few months (years?) I know I'd need to worry about scaling the site up and out, since the resources it would end up consuming would be huge. So, this got me to thinking, when is the best time to start thinking about, and designing for, scalability? If you start too early on, you could easily over complicate your design, and make it impossible to actually build. You could also get too caught up in the details, the architecture, whatever, and wind up getting nothing done. Also, if you do get it working, but the site never takes off, you may have wasted a good chunk of extra effort. On the other hand, you could be saving yourself a ton of effort down the road. Designing it from the ground up to be big would make it much easier later on to let it grow big, with very little rewriting going on. I know for what I'm working on, I've decided to make at least a few choices now on the side of scaling, but I'm not going to do a complete change of thinking to get it to scale completely. Notably, I've redesigned my database from a conventional relational design to one similar to what was suggested on the Reddit site linked below, and I'm going to give memcache a try. So, the basic question, when is a good time to start thinking or worrying about scaling, and what are some good designs, tips, etc. for when doing so? A couple of things I've been reading, for those who are interested: http://www.codinghorror.com/blog/2009/06/scaling-up-vs-scaling-out-hidden-costs.html http://highscalability.com/blog/2010/5/17/7-lessons-learned-while-building-reddit-to-270-million-page.html http://developer.yahoo.com/performance/rules.html

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  • OO vs Simplicity when it comes to user interaction

    - by Oetzi
    Firstly, sorry if this question is rather vague but it's something I'd really like an answer to. As a project over summer while I have some downtime from Uni I am going to build a monopoly game. This question is more about the general idea of the problem however, rather than the specific task I'm trying to carry out. I decided to build this with a bottom up approach, creating just movement around a forty space board and then moving on to interaction with spaces. I realised that I was quite unsure of the best way of proceeding with this and I am torn between two design ideas: Giving every space its own object, all sub-classes of a Space object so the interaction can be defined by the space object itself. I could do this by implementing different land() methods for each type of space. Only giving the Properties and Utilities (as each property has unique features) objects and creating methods for dealing with the buying/renting etc in the main class of the program (or Board as I'm calling it). Spaces like go and super tax could be implemented by a small set of conditionals checking to see if player is on a special space. Option 1 is obviously the OO (and I feel the correct) way of doing things but I'd like to only have to handle user interaction from the programs main class. In other words, I don't want the space objects to be interacting with the player. Why? Errr. A lot of the coding I've done thus far has had this simplicity but I'm not sure if this is a pipe dream or not for larger projects. Should I really be handling user interaction in an entirely separate class? As you can see I am quite confused about this situation. Is there some way round this? And, does anyone have any advice on practical OO design that could help in general?

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