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  • Avoiding Object Oriented Pitfalls, Migrating from C, What Worked for You?

    - by Stephen
    I've been programming in procedural languages for quite some time now, and my first reaction to a problem is to start breaking it down into tasks to perform rather than to consider the different entities (objects) that exist and their relationships. I have had a university course in OOP, and understand the fundamentals of encapsulation, data abstraction, polymorphism, modularity and inheritance. I read Learning to think in the Object Oriented Way and Learning object oriented thinking, and will be looking at some of the books pointed to in those answers. I think that several of my medium to large sized projects will benefit from effective use of OOP but as a novice I would like to avoid time consuming, common errors. Based on your experiences, what are these pitfalls and what are reasonable ways around them? If you could explain why they are pitfalls, and how your suggestion is effective in addressing the issue it'd be appreciated. I'm thinking along the lines of something like "Is it common to have a fair number of observer and modifier methods and use private variables or are there techniques for consolidating/reducing them?" I'm not worried about using C++ as a pure OO language, if there are good reasons to mix methods. (Reminiscent of the reasons to use GOTOs, albeit sparingly.) Thank you!

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  • DB Object passing between classes singleton, static or other?

    - by Stephen
    So I'm designing a reporting system at work it's my first project written OOP and I'm stuck on the design choice for the DB class. Obviously I only want to create one instance of the DB class per-session/user and then pass it to each of the classes that need it. What I don't know it what's best practice for implementing this. Currently I have code like the following:- class db { private $user = 'USER'; private $pass = 'PASS'; private $tables = array( 'user','report', 'etc...'); function __construct(){ //SET UP CONNECTION AND TABLES } }; class report{ function __construct ($params = array(), $db, $user) { //Error checking/handling trimed //$db is the database object we created $this->db = $db; //$this->user is the user object for the logged in user $this->user = $user; $this->reportCreate(); } public function setPermission($permissionId = 1) { //Note the $this->db is this the best practise solution? $this->db->permission->find($permissionId) //Note the $this->user is this the best practise solution? $this->user->checkPermission(1) $data=array(); $this->db->reportpermission->insert($data) } };//end report I've been reading about using static classes and have just come across Singletons (though these appear to be passé already?) so what's current best practice for doing this?

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  • redoing object model construction to fit with asynchronous data fetching

    - by Andrew Patterson
    I have a modeled a set of objects that correspond with some real world concepts. TradeDrug, GenericDrug, TradePackage, DrugForm Underlying the simple object model I am trying to provide is a complex medical terminology that uses numeric codes to represent relationships and concepts, all accessible via a REST service - I am trying to hide away some of that complexity with an object wrapper. To give a concrete example I can call TradeDrug d = Searcher.FindTradeDrug("Zoloft") or TradeDrug d = new TradeDrug(34) where 34 might be the code for Zoloft. This will consult a remote server to find out some details about Zoloft. I might then call GenericDrug generic = d.EquivalentGeneric() System.Out.WriteLine(generic.ActiveIngredient().Name) in order to get back the generic drug sertraline as an object (again via a background REST call to the remote server that has all these drug details), and then perhaps find its ingredient. This model works fine and is being used in some applications that involve data processing. Recently however I wanted to do a silverlight application that used and displayed these objects. The silverlight environment only allows asynchronous REST/web service calls. I have no problems with how to make the asychhronous calls - but I am having trouble with what the design should be for my object construction. Currently the constructors for my objects do some REST calls sychronously. public TradeDrug(int code) { form = restclient.FetchForm(code) name = restclient.FetchName(code) etc.. } If I have to use async 'events' or 'actions' in order to use the Silverlight web client (I know silverlight can be forced to be a synchronous client but I am interested in asychronous approaches), does anyone have an guidance or best practice for how to structure my objects. I can pass in an action callback to the constructor public TradeDrug(int code, Action<TradeDrug> constructCompleted) { } but this then allows the user to have a TradeDrug object instance before what I want to construct is actually finished. It also doesn't support an 'event' async pattern because the object doesn't exist to add the event to until it is constructed. Extending that approach might be a factory object that itself has an asynchronous interface to objects factory.GetTradeDrugAsync(code, completedaction) or with a GetTradeDrugCompleted event? Does anyone have any recommendations?

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  • Blob object not working properly even though the class is seralized

    - by GustlyWind
    I have class which is seralized and does convert a very large amount of data object to blob to save it to database.In the same class there is decode method to convert blob to the actual object.Following is the code for encode and decode of the object. private byte[] encode(ScheduledReport schedSTDReport) { byte[] bytes = null; try { ByteArrayOutputStream bos = new ByteArrayOutputStream(); ObjectOutputStream oos = new ObjectOutputStream(bos); oos.writeObject(schedSTDReport); oos.flush(); oos.close(); bos.close(); //byte [] data = bos.toByteArray(); //ByteArrayOutputStream baos = new ByteArrayOutputStream(); //GZIPOutputStream out = new GZIPOutputStream(baos); //XMLEncoder encoder = new XMLEncoder(out); //encoder.writeObject(schedSTDReport); //encoder.close(); bytes = bos.toByteArray(); //GZIPOutputStream out = new GZIPOutputStream(bos); //out.write(bytes); //bytes = bos.toByteArray(); } catch (Exception e) { _log.error("Exception caught while encoding/zipping Scheduled STDReport", e); } decode(bytes); return bytes; } /* * Decode the report definition blob back to the * ScheduledReport object. */ private ScheduledReport decode(byte[] bytes) { ByteArrayInputStream bais = new ByteArrayInputStream(bytes); ScheduledReport sSTDR = null; try { ObjectInputStream ois = new ObjectInputStream(bais); //GZIPInputStream in = new GZIPInputStream(bais); //XMLDecoder decoder = new XMLDecoder(in); sSTDR = (ScheduledReport)ois.readObject();//decoder.readObject(); //decoder.close(); } catch (Exception e) { _log.error("IOException caught while decoding/unzipping Scheduled STDReport", e); } return sSTDR; } The problem here is whenver I change something else in this class means any other method,a new class version is created and so the new version the class is unable to decode the originally encoded blob object. The object which I am passing for encode is also seralized object but this problem exists. Any ideas thanks

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  • Encapsulate update method inside of object or have method which accepts an object to update

    - by Tom
    Hi, I actually have 2 questions related to each other: I have an object (class) called, say MyClass which holds data from my database. Currently I have a list of these objects ( List < MyClass ) that resides in a singleton in a "communal area". I feel it's easier to manage the data this way and I fail to see how passing a class around from object to object is beneficial over a singleton (I would be happy if someone can tell me why). Anyway, the data may change in the database from outside my program and so I have to update the data every so often. To update the list of the MyClass I have a method called say, Update, written in another class which accepts a list of MyClass. This updates all the instances of MyClass in the list. However would it be better instead to encapulate the Update() method inside the MyClass object, so instead I would say foreach(MyClass obj in MyClassList) { obj.update(); } What is a better implementation and why? The update method requires a XML reader. I have written an XML reader class which is basically a wrapper over the standard XML reader the language natively provides which provides application specific data collection. Should the XML reader class be in anyway in the "inheritance path" of the MyClass object - the MyClass objects inherits from the XML reader because it uses a few methods. I can't see why it should. I don't like the idea of declaring an instance of the XML Reader class inside of MyClass and an MyClass object is meant to be a simple "record" from the database and I feel giving it loads of methods, other object instances is a bit messy. Perhaps my XML reader class should be static but C#'s native XMLReader isn't static.? Any comments would be greatly appreciated Thanks Thomas

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  • Using Zope object unique id ( _p_oid ) to access object itself

    - by Alex M
    Every Zope object has it's own unique id ( _p_oid ). To convert it into integer value: from Shared.DC.xml.ppml import u64 as decodeObjectId oid = decodeObjectId(getattr(<Object instance>, '_p_oid')) Is it possible to get object itself having it's _p_oid? I tried this: from ZODB.utils import p64 object = <RootObject instance>._p_jar[p64(oid)] But it seems it's a wrong way

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  • using Visual Studio 2010 and speech recognition on windows 7?

    - by Kevin Won
    I've never used Speech Recognition (SR) at all, but I'm hearing that the built-in SR capabilities of windows 7 is not half-bad. I'm thinking that it might be a real productivity booster with Visual Studio so I can decrease the use of the mouse (no Emacs comments please ;-). I don't envision not using the keyboard to type the actual code--but maybe that would work too? Does anyone have experience using SR with Visual Studio on Windows 7? If so, any tips on usage?

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  • Open Source .Net Object Database or Document Database for use in Hosted environment

    - by runxc1 Bret Ferrier
    I am looking at creating a web site and I want to try and learn either a Object Database or a Document Database. I am going to be using a hosting provider so I won't be able to install any software. I am unable to purchase any licensing so I need to be able use either a free or open source Object/Document Database. Are there any free Object/Document Databases that don't require installation of some sort?

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  • Passing object from PHP to Mysql Stored procedure

    - by user268982
    Hi All, Scenario :- I have to call MYSQL stored procedure from PHP and do some operations ( around 15 commands ) on the database Problem :- I have to call stored procedure with 36 parameters. Lot of parameters . I don't think it is a good idea to pass these many individual parameters and even heard passing individul parameters increases network traffic. Looking for :- I created a Data Object at PHP side and is there any way I can create similar kind of Object in MYSQL and pass this object as a parameter and extract the data from the object in MYSQL stored procedure Thanks for your help Regards Kiran

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  • PHP, jQuery and Ajax Object Orientation

    - by pastylegs
    I'm a fairly experienced programmer getting my head around PHP and Ajax for the first time, and I'm having a bit of trouble figuring out how to incorperate object oriented PHP into my ajax webapp. I have an admin page (admin.php) that will load and write information (info.xml) from an XML file depending on the users selection of a form on the admin page. I have decided to use an object (ContentManager.php) to manage the loading and writing of the XML file to disk, i.e : class ContentManager{ var $xml_attribute_1 ... function __construct(){ //load the xml file from disk and save its contents into variables $xml_attribute = simplexml_load_file(/path/to/xml) } function get_xml_contents(){ return xml_attribute; } function write_xml($contents_{ } function print_xml(){ } } I create the ContentManager object in admin.php like so <?php include '../includes/CompetitionManager.php'; $cm = new CompetitionManager() ?> <script> ...all my jquery </script> <html> ... all my form elements </html> So now I want to use AJAX to allow the user to retrieve information from the XML file via the ContentManger app using an interface (ajax_handler.php) like so <?php if(_POST[]=="get_a"){ }else if() } ... ?> I understand how this would work if I wasn't using objects, i.e. the hander php file would do a certain action depending on a variable in the .post request, but with my setup, I can't see how I can get a reference to the ContentManager object I have created in admin.php in the ajax_handler.php file? Maybe my understanding of php object scope is flawed. Anyway, if anyone can make sense of what I'm trying to do, I would appreciate some help!

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  • Explore a COM Object in PHP

    - by shaiss
    What would be the proper way to explode a COM object for debugging? I have a 3rd party function that returns a multilevel object. The documentation is non existant, so I'd like to be able to echo everything out of the object or debug it in Komodo IDE. Komodo just says Object and nothing else. Maybe convert to array? I know some of the existing options such as $com->Status, but there are more variables returned that I'd like to know what they are.

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  • python object AttributeError: type object 'Track' has no attribute 'title'

    - by ccwhite1
    I apologize if this is a noob question, but I can't seem to figure this one out. I have defined an object that defines a music track (NOTE: originally had the just ATTRIBUTE vs self.ATTRIBUTE. I edited those values in to help remove confusion. They had no affect on the problem) class Track(object): def __init__(self, title, artist, album, source, dest): """ Model of the Track Object Contains the followign attributes: 'Title', 'Artist', 'Album', 'Source', 'Dest' """ self.atrTitle = title self.atrArtist = artist self.atrAlbum = album self.atrSource = source self.atrDest = dest I use ObjectListView to create a list of tracks in a specific directory ....other code.... self.aTrack = [Track(sTitle,sArtist,sAlbum,sSource, sDestDir)] self.TrackOlv.AddObjects(self.aTrack) ....other code.... Now I want to iterate the list and print out a single value of each item list = self.TrackOlv.GetObjects() for item in list: print item.atrTitle This fails with the error AttributeError: type object 'Track' has no attribute 'atrTitle' What really confuses me is if I highlight a single item in the Object List View display and use the following code, it will correctly print out the single value for the highlighted item list = self.TrackOlv.GetSelectedObject() print list.atrTitle

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  • Dynamically add a field to an object in matlab

    - by Marc
    Say I have a MATLAB object defined in a class file classdef foo properties bar end end And I create a foo object myfoo = foo(); Now I want to add another field to foo dynamically. What I want is foo.newfield = 42; but this will throw an error. I know there is a way to dynamically add a field/property to a MATLAB object but I can't remember it or find it easily in the help. Anyone know the syntax?

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  • Object Oriented Database - why most of the companies do not use them

    - by GigaPr
    Hi, I am pretty new to programming(just finished University). I have been thought in the last 4 years about Object Oriented development and the numerous advantages of this approach. My question is Isn't it easier to use a pure Object Oriented database in development applications? Why Object Oriented database are not as much diffuse as relational? From my point of view makes sense to use OO database, the latter will avoid the numerous construction necessary for the mapping of complex objects on the tables.

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  • reinitializing javascript object's properties

    - by Pino
    In my Javascript drag and drop build app, a variety of buildings can be built. The specific characteristics of these are all saved in one object, like var buildings = { house: ['#07DA21',12,12,0,20], bank: ['#E7DFF2',16,16,0,3], stadium: ['#000000',12,12,0,1], townhall: ['#2082A8',20,8,0,1], etcetera } So every building has a number of characteristics, like color, size, look which can be called as buildings[townhall][0] (referring to the color). The object changes as the user changes things. When clicking 'reset' however, the whole object should be reset to its initial settings again to start over, but I have no idea how to do that. For normal objects it is something like. function building() {} var building = new building(); delete building; var building2 = new building(); You can easily delete and remake it, so the properties are reset. But my object is automatically initialized. Is there a way to turn my object into something that can be deleted and newly created, without making it very complicating, or a better way to store this information?

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  • ASP.NET "Object reference not set..." error

    - by Roman
    Hi, I have a website written using ASP.NET. We have a development machine and a deployment server. The site works great on the development machine, but when is transfered (using simple FTP Upload) generates strange behavior. It starts working just fine, but after a while stops working and throws an exception "Exception: Object reference not set to an instance of an object.". The deal is that the absolute path of the website on the development machine is different than on the deployment server (and why should they be similar?) and the exact error is: Exception: Object reference not set to an instance of an object. at SOMEPROJECT_Objects.Player..ctor(Int32 PlayerID) in C:\inetpub\wwwroot\SOMEPROJECTSolution\ALLPROJECT\SOMEPROJECT_Objects\Player.cs:line 123 at SOMEPROJECT_GameLayer.M_Game.PlayerActiveGame(Int32 PlayerID) in C:\inetpub\wwwroot\SOMEPROJECTSolution\ALLPROJECT\SOMEPROJECT_GameLayer\M_Game.cs:line 85 at Web.getsms.Page_Load(Object sender, EventArgs e) in C:\inetpub\wwwroot\SOMEPROJECTSolution\ALLPROJECT\SOMEPROJECT-sms\Web\getsms.aspx.cs:line 59 The address that it is looking for is the address on the DEVELOPMENT machine, where as the site now resides on the deployment server. Any ideas why this happens would be appreciated. Thanks, Roman

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  • How to generate a checksum for an java object

    - by Alex
    hi there, I'm looking for an solution to generate a checksum for any type of java object, which remains the same for every exection of an application which produces the same object. I tried it with object.hashcode(), but as I read in the api ....This integer need not remain consistent from one execution of an application to another execution of the same application. thank you, best regard alex

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