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  • Looking for some OO design advice

    - by Andrew Stephens
    I'm developing an app that will be used to open and close valves in an industrial environment, and was thinking of something simple like this:- public static void ValveController { public static void OpenValve(string valveName) { // Implementation to open the valve } public static void CloseValve(string valveName) { // Implementation to close the valve } } (The implementation would write a few bytes of data to the serial port to control the valve - an "address" derived from the valve name, and either a "1" or "0" to open or close the valve). Another dev asked whether we should instead create a separate class for each physical valve, of which there are dozens. I agree it would be nicer to write code like PlasmaValve.Open() rather than ValveController.OpenValve("plasma"), but is this overkill? Also, I was wondering how best to tackle the design with a couple of hypothetical future requirements in mind:- We are asked to support a new type of valve requiring different values to open and close it (not 0 and 1). We are asked to support a valve that can be set to any position from 0-100, rather than simply "open" or "closed". Normally I would use inheritance for this kind of thing, but I've recently started to get my head around "composition over inheritance" and wonder if there is a slicker solution to be had using composition?

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  • Identity Map Pattern and the Entity Framework

    - by nikolaosk
    This is going to be the seventh post of a series of posts regarding ASP.Net and the Entity Framework and how we can use Entity Framework to access our datastore. You can find the first one here , the second one here and the third one here , the fourth one here , the fifth one here and the sixth one here . I have a post regarding ASP.Net and EntityDataSource. You can read it here .I have 3 more posts on Profiling Entity Framework applications. You can have a look at them here , here and here . In...(read more)

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  • Is there any reason to use "container" classes?

    - by Michael
    I realize the term "container" is misleading in this context - if anyone can think of a better term please edit it in. In legacy code I occasionally see classes that are nothing but wrappers for data. something like: class Bottle { int height; int diameter; Cap capType; getters/setters, maybe a constructor } My understanding of OO is that classes are structures for data and the methods of operating on that data. This seems to preclude objects of this type. To me they are nothing more than structs and kind of defeat the purpose of OO. I don't think it's necessarily evil, though it may be a code smell. Is there a case where such objects would be necessary? If this is used often, does it make the design suspect?

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  • How much is modern programming still tied to underyling digital logic?

    - by New Talk
    First of all: I've got no academic background. I'm working primarily with Java and Spring and I'm also fond of web programming and relational databases. I hope I'm using the right terms and I hope that this vague question makes some sense. Today the following question came to my mind: How much is modern programming still tied to the underlying digital logic? With modern programming I mean concepts like OOP, AOP, Java 7, AJAX, … I hope you get the idea. Do they no longer need the digital logic with which computers are working internally? Or is binary logic still ubiquitous when programming this way? If I'd change the inner workings of a computer overnight, would it matter, because my programming techniques are already that abstract? P. S.: With digital logic I mean the physical representation of everything "inside" the computer as zeroes and ones. Changed "binary" to "digital".

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  • Describe business logic with diagrams

    - by Nikos M.
    I am currently developing a web application for my thesis.I was asked by my professor to make diagrams to describe the business logic. Since I don't have a prior experience, I am pretty confused with all the terminology. I managed to clarify,I think, what business rules and business logic are, but I can't find out how you describe the business logic. Is it something particular or is it something more general? Do I need to learn UML? Does the fact that I use MVC affects the way I'll describe it?

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  • Determine percentage of screen covered by an object without using frustum culling

    - by Meltac
    On the CPU-side of an 3D first-person / ego perspective game I need to check whether what the players currently sees on screen is the inside of a box object defined by world space coordinates (the player might be outside of that box but on screen sees only/mostly the inside of the box, or vice-versa, looks from within the box to the outside). The "casual" way of performing such a check would incorporate frustum culling but such an approach would be hard to achieve with my given set of engine parameters which I'd like to avoid if there is a simpler way. What I actually have at the point where I would like to do the check (high-level script on CPU, not GPU side): Camera world position Camera direction Camera FOV Two Box corner world coordinates (left-bottom-front, right-top-back) What I do not have right away: View frustrum definition (near/far plane or say 6 planes defining frustum) Any specific pixel information (uv, view space position, depth or the like) What I would like to calculate: Percentage of screen "covered" by box. Any hints on how to perform such calculation?

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  • Make my website dynamically loaded data available to Facebook Open Graph Object Scrapper

    - by fvaliquette
    Here is the design of my web site: The user enter myWebsite.com/a/1 .htaccess rules redirect to myWebsite.com/b Now the JavaScript ExtJS library is loading. Extracting the value from the URL (in this case it is “1”) Loading ./xml/1.xml From 1.xml setting the Open Graph data (Title, type, image, etc) Loading data that will be shown to the user from 1.xml into the website. My question is: How can I make the Open Graph data available to Facebook? Facebook do not to load my ExtJS JavaScript Library before extracting the Open Graph Object values from the HTML. Is there an easy solution to this problem? The only solutions I found is to make statics web pages or dynamically pages rendered on the server side but I would like to avoid these since my web page implementation is already finished and I would like to avoid re working on it.

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  • Explanation on how "Tell, Don't Ask" is considered good OO

    - by Pubby
    This blogpost was posted on Hacker News with several upvotes. Coming from C++, most of these examples seem to go against what I've been taught. Such as example #2: Bad: def check_for_overheating(system_monitor) if system_monitor.temperature > 100 system_monitor.sound_alarms end end versus good: system_monitor.check_for_overheating class SystemMonitor def check_for_overheating if temperature > 100 sound_alarms end end end The advice in C++ is that you should prefer free functions instead of member functions as they increase encapsulation. Both of these are identical semantically, so why prefer the choice that has access to more state? Example 4: Bad: def street_name(user) if user.address user.address.street_name else 'No street name on file' end end versus good: def street_name(user) user.address.street_name end class User def address @address || NullAddress.new end end class NullAddress def street_name 'No street name on file' end end Why is it the responsibility of User to format an unrelated error string? What if I want to do something besides print 'No street name on file' if it has no street? What if the street is named the same thing? Could someone enlighten me on the "Tell, Don't Ask" advantages and rationale? I am not looking for which is better, but instead trying to understand the author's viewpoint.

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  • Question about SDLC. How to answer this?

    - by pirzada
    I have seen this asked many times in job interviews but I am still not sure how to answer this. I am a web developer for quite some time but I still have problem with explaining OOP and SDLC (Familiar with system development life cycle) . How to prepare for above 2 topics for an interview point of view. Still I use both all the time during development. I am not clear on OOP SDLC Is there any simplest answer to both of these? Thanks

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  • Oracle sort Oracle Application Express 4.2, son outil de développement rapide intégré à Oracle Database

    Oracle Application Express, l'outil de développement rapide d'Oracle est désormais disponible en version 4.2. Cet outil, intégré à Oracle Database sans coût supplémentaire, permet de développer des applications Web exploitant les données d'une base Oracle. Cette mise à jour est très centrée vers le mobile et apporte un certain nombre de nouveautés pour le développement d'applications mobiles avec APEX. Notons en particulier :Le rendu des applications qui s'adaptent pour proposer une interface adaptée au terminal mobile utilisé L'utilisation de jQuery Mobile qui permet la compatibilité sur la majorité des terminaux sans modification La possibilité de créer des graphiques en HTML5 pour les terminaux ne disposant pas de Flash L'utilisat...

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  • Fundamental programming book [closed]

    - by Luke Annison
    I'm a fairly new programmer and currently learning ruby on rails with the intention of developing a web application. I am currently going reading Agile Web Development with Rails 4th Edition and its working well for me, however I'm wondering if somebody can recommend a more general, almost classic book to read casually alongside to help cement the fundamentals in place. As I said, I'm for the most part a beginner and the only education I've had is this and briefly one other technical book, so I'm sure there must be some "must reads" out there that give me a more substantial context for the basics of either Ruby on Rails, Ruby, objective oriented programming, or programming in general. What books helped you grasp a deeper and more rounded understanding of your skills as a programmer? All suggestions are welcome and appreciated.

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  • how do you read from system.out in Java [closed]

    - by Dan
    I'm trying to create a word scramble game and so far I have taken a vector of randomly assorted strings that contains both words and hints and split them into two vectors. I have randomly scrambled the word and set this all up in text boxes. Right now I'm stuck because I have a text box that takes input but I'm not sure how to read that in? I want the user to type the unscrambled word into the text box and have it calculate as correct and move on to the next word immediately. I also don't know how to get the keys working. I want the "?" character to be the hint button that shows the hint. At the moment the hint box works if I type the question mark in using the System.in but it doesn't work if I type it directly in to the text box. The characters are showing up in the text box but nothing is working after that.

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  • Save match details to SQLite or XML?

    - by trizz
    I'm making a (conceptual) system to simulate any kind of sports match (like soccer,basketball,etc) with actions (for example pass,pass,out,pass,score) so it will be like a real report. The main statistics (play time, number of actions etc.) I'm saving to a MySQL database, but the report itself, can contain more than 1000 actions per match. To avoid millions of records in my database I'm thinking of saving the detailled report in a SQLite database or a XML file. For every match played, a file will be created. When a user request the match details, I read the file for details. What is the best choice for this purpose? SQLite or XML?

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  • Good Software Architecture book or material?

    - by Inder Kumar Rathore
    I am a programmer and there is always a word going around about the architecture of the application/software. I want to gain some knowledge about how to develop good architecture. I know it is something that comes with the experience but I need some start so that I can practice it and get some good experience. So Please refer a good book for architecture. I know "Head first design patterns" is there, should I go for it or is there some good books also. Thanks

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  • Any language where every class instance is a class too?

    - by Dokkat
    Taking inspiration from Javascript prototypes, I had the idea of a language where every instance can be used as a class. Before I potentially reinvent the wheel, I would like to ask if there is a language already using this concept: //To declare a Class, extend the base class (in this case, Type) Type(Weapon,{price:0}); //Same syntax to inherit; simply extend the parent: Weapon(Sword,{price:3}); Weapon(Axe,{price:4}); Sword(Katana,{price:7}); Sword(Dagger,{price:3}); //And the same to create an instance: Katana(myKatana,{nickname:"Leon"}); myKatana.price; // 7 myKatana.nickname; // Leon // An operator to return children of a class; Sword_; // [Katana, Dagger] // An operator to return array of descendants; Sword__; // [Katana, Dagger, myKatana] // An operator to return array of parents; Sword^; // Weapon // Arrays can be used as elements Sword__.price += 1; //increases price of Sword's descendants by 1 mySword.price; //8 // And to access specific element (using its name instead of index) var name = "mySword" Katana_[name]; // [mySword] Katana_[name].nickname; // Leon Has this kind of approach been already studied/implemented?

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  • Something similar to Objective-C categories in other languages?

    - by adig
    I understand Objective-C categories and how they become useful, but I always have a hard time explaining the concept to other programmers that are not familiar with Objective C. Maybe I'm just bad at explaining things, but I was thinking at another way to explain it by comparing to similar features offered by other (more popular) languages. (ex : I can explain the similarities between Objective C protocols and Java Interfaces) Any examples similar to Categories ?

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  • SANS Webcast: Label Based Access Controls in Oracle Database 11g

    - by Troy Kitch
    Controlling access to data subsets within an application table can be difficult and inefficient especially when faced with specific data ownership, consolidation and multi-tenancy requirements. However, this can be elegantly addressed using label based access control (LBAC). In this webcast you will learn how LBAC using Oracle Label Security and Oracle Database 11g can easily enforce row-level access based on user security clearance. In addition, Oracle security experts will discuss real world case studies demonstrating how customers, in industries ranging from retail to government, are relying on Oracle Label Security for virtual information partitioning and secure consolidation of information.  Register for the July 12 webcast now.

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  • How to refactor an OO program into a functional one?

    - by Asik
    I'm having difficulty finding resources on how to write programs in a functional style. The most advanced topic I could find discussed online was using structural typing to cut down on class hierarchies; most just deal with how to use map/fold/reduce/etc to replace imperative loops. What I would really like to find is an in-depth discussion of an OOP implementation of a non-trivial program, its limitations, and how to refactor it in a functional style. Not just an algorithm or a data structure, but something with several different roles and aspects - a video game perhaps. By the way I did read Real-World Functional Programming by Tomas Petricek, but I'm left wanting more.

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  • Which paradigm to use for writing chess engine?

    - by poke
    If you were going to write a chess game engine, what programming paradigm would you use (OOP, procedural, etc) and why whould you choose it ? By chess engine, I mean the portion of a program that evaluates the current board and decides the computer's next move. I'm asking because I thought it might be fun to write a chess engine. Then it occured to me that I could use it as a project for learning functional programming. Then it occured to me that some problems aren't well suited to the functional paradigm. Then it occured to me that this might be good discussion fodder.

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  • How to depict Import a file action in the Sequence diagram

    - by user970696
    Everyone says sequence diagrams are so easy but I just cannot figure this out. Basically user clicks on an 'Import from temp folder' button, the program opens a window with a list populated with filenames, user clicks on a filename, clicks on OK and the document is imported. I know the order of the actions but how to depict e.g. populating a list, or selecting an item from a list? So I assume the objects would be like: [USER] [ImportDialogWindow] [ListOfFiles:STRING] [?where to go with selected file]

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  • Understanding Visitor Pattern

    - by Nezreli
    I have a hierarchy of classes that represents GUI controls. Something like this: Control-ContainerControl-Form I have to implement a series of algoritms that work with objects doing various stuff and I'm thinking that Visitor pattern would be the cleanest solution. Let take for example an algorithm which creates a Xml representaion of a hierarchy of objects. Using 'classic' approach I would do this: public abstract class Control { public virtual XmlElement ToXML(XmlDocument document) { XmlElement xml = document.CreateElement(this.GetType().Name); // Create element, fill it with attributes declared with control return xml; } } public abstract class ContainerControl : Control { public override XmlElement ToXML(XmlDocument document) { XmlElement xml = base.ToXML(document); // Use forech to fill XmlElement with child XmlElements return xml; } } public class Form : ContainerControl { public override XmlElement ToXML(XmlDocument document) { XmlElement xml = base.ToXML(document); // Fill remaining elements declared in Form class return xml; } } But I'm not sure how to do this with visitor pattern. This is the basic implementation: public class ToXmlVisitor : IVisitor { public void Visit(Form form) { } } Since even the abstract classes help with implementation I'm not sure how to do that properly in ToXmlVisitor. Perhaps there is a better solution to this problem. The reason that I'm considering Visitor pattern is that some algorithms will need references not available in project where the classes are implemented and there is a number of different algorithms so I'm avoiding large classes. Any thoughts are welcome.

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  • software architecture (OO design) refresher course

    - by PeterT
    I am lead developer and team lead in a small RAD team. Deadlines are tight and we have to release often, which we do, and this is what keep the business happy. While we (the development team) are trying to maintain the quality of the code (clean and short methods), I can't help but notice that the overall quality of the OO design&architecture is getting worse over the time - the library we are working on is gradually reducing itself to a "bag of functions". Well, we try to use the design patterns, but since we don't really have much time for a design as such we are mostly using the creational ones. I have read Code Complete / Design Patterns (GOF & enterprise) / Progmatic Programmer / and many books from Effective XXX series. Should I re-read them again as I have read them a long time ago and forgotten quite a lot, or there are other / better OO design / software architeture books been published since then which I should definitely read? Any ideas, recommendations on how can I get the situation under control and start improving the architecture. The way I see it - I will start improving the architectural / design quality of software components I am working on and then will start helping other team members once I find what is working for me.

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  • OOP - Composition, Components and Composites Example?

    - by coder3
    I've been reading a bit about OOP in relation to Composition, Components and Composites. I believe I understand the fundamental principle (not sure). Can some one please provide a code example of a person or car (both have many properties) using Composition, Components and Composites. I think seeing it in code would clear up the confusion I have regarding this pattern. Preferably in Java or PHP - many thanks!

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  • How to explain OOP to a matlab programmer?

    - by Oak
    I have a lot of friends who come from electrical / physical / mechanical engineering background, and are curious about what is "OOP" all about. They all know Matlab quite well, so they do have basic programming background; but they have a very hard time grasping a complex type system which can benefit from the concepts OOP introduces. Can anyone propose a way I can try to explain it to them? I'm just not familiar with Matlab myself, so I'm having troubles finding parallels. I think using simple examples like shapes or animals is a bit too abstract for those engineers. So far I've tried using a Matrix interface vs array-based / sparse / whatever implementations, but that didn't work so well, probably because different matrix types are already well-supported in Matlab.

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  • Updating a database connection password using a script

    - by Tim Dexter
    An interesting customer requirement that I thought was worthy of sharing today. Thanks to James for the requirement and Bryan for the proposed solution and me for testing the solution and proving it works :0) A customers implementation of Sarbanes Oxley requires them to change all database account passwords every 90 days. This is scripted leveraging shell scripts today for most of their environments. But how can they manage the BI Publisher connections? Now, the customer is running 11g and therefore using weblogic on the middle tier, which is the first clue to Bryans proposed solution. To paraphrase and embellish Bryan's solution a little; why not use a JNDI connection from BIP to the database. Then employ the web logic scripting engine to make updates to the JNDI as needed? BIP is completely uninvolved and with a little 'timing' users will be completely unaware of the password updates i.e. change the password when reports are not being executed. Perfect! James immediately tracked down the WLST script that could be used here, http://middlewaremagic.com/weblogic/?p=4261 (thanks Ravish) Now it was just a case of testing the theory. Some steps: Create the JNDI connection in WLS Create the JNDI connection in BI Publisher pointing to the WLS connection Build new data models using or re-point data sources to use the JNDI connection. Create the WLST script to update the WLS JNDI password as needed. Test! Some details. Creating the JNDI connection in web logic is pretty straightforward. Log into hte console and look for Data Sources under the Services section of the home page and click it Click New >> Generic Datasource Give the connection a name. For the JNDI name, prefix it with 'jdbc/' so I have 'jdbc/localdb' - this name is important you'll need it on the BIP side. Select your db type - this will influence the drivers and information needed on the next page. Being a company man, Im using an Oracle db. Click Next Select the driver of choice, theres lots I know, you can read about them I just chose 'Oracle's Driver (Thin) for Instance connections; Versions 9.0.1 and later' Click Next >> Next Fill out the db name (SID), server, port, username to connect and password >> Next Test the config to ensure you can connect. >> Next Now you need to deploy the connection to your BI server, select it and click Next. You're done with the JNDI config. Creating the JNDI connection on the Publisher side is covered here. Just remember to the connection name you created in WLS e.g. 'jdbc/localdb' Not gonna tell you how to do this, go read the user guide :0) Suffice to say, it works. This requires a little reading around the subject to understand the scripting engine and how to execute scripts. Nicely covered here. However a bit of googlin' and I found an even easier way of running the script. ${ServerHome}/common/bin/wlst.sh updatepwd.py Where updatepwd.py is my script file, it can be in another directory. As part of the wlst.sh script your environment is set up for you so its very simple to execute. The nitty gritty: Need to take Ravish's script above and create a file with a .py extension. Its going to need some modification, as he explains on the web page, to make it work in your environment. I played around with it for a while but kept running into errors. The script as is, tries to loop through all of your connections and modify the user and passwords for each. Not quite what we are looking for. Remember our requirement is to just update the password for a given connection. I also found another issue with the script. WLS 10.x does not allow updates to passwords using clear type ie un-encrypted text while the server is in production mode. Its a bit much to set it back to developer mode bounce it, change the passwords and then bounce and then change back to production and bounce again. After lots of messing about I finally came up with the following: ############################################################################# # # Update password for JNDI connections # ############################################################################# print("*** Trying to Connect.... *****") connect('weblogic','welcome1','t3://localhost:7001') print("*** Connected *****") edit() startEdit() print ("*** Encrypt the password ***") en = encrypt('hr') print "Encrypted pwd: ", en print ("*** Changing pwd for LocalDB ***") dsName = 'LocalDB' print 'Changing Password for DataSource ', dsName cd('/JDBCSystemResources/'+dsName+'/JDBCResource/'+dsName+'/JDBCDriverParams/'+dsName) set('PasswordEncrypted',en) save() activate() Its pretty simple and you can expand on it to loop through the data sources and change each as needed. I have hardcoded the password into the file but you can pass it as a parameter as needed using the properties file method. Im not going to get into the detail of that here but its covered with an example here. Couple of points to note: 1. The change to the password requires a server bounce to get the changes picked up. You can add that to the shell script you will use to call the script above. 2. The script above needs to be run from the MW_HOME\user_projects\domains\bifoundation_domain directory to get the encryption libraries set correctly. My command to run the whole script was: d:\oracle\bi_mw\wlserver_10.3\common\bin\wlst.cmd updatepwd.py - where wlst.cmd is the scripting command line and updatepwd.py was my update password script above. I have not quite spoon fed everything you need to make it a robust script but at least you know you can do it and you can work out the rest I think :0)

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