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  • C++ Singleton design pattern

    - by Artem Barger
    Recently I've bumped into a realization/implementation of the Singleton design pattern for C++. It has looked like this (I have adopted it from the real life example): // a lot of methods are omitted here class Singleton { public: static Singleton* getInstance( ); ~Singleton( ); private: Singleton( ); static Singleton* instance; }; From this declaration I can deduce that the instance field is initiated on the heap. That means there is a memory allocation. What is completely unclear for me is when exactly the memory is going to be deallocated? Or is there a bug and memory leak? It seems like there is a problem in the implementation. My main question is, how do I implement it in the right way?

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  • How to implement the disposable pattern in a class that inherits from another disposable class?

    - by TheRHCP
    Hi, I often used the disposable pattern in simple classes that referenced small amount of resources, but I never had to implement this pattern on a class that inherits from another disposable class and I am starting to be a bit confused in how to free the whole resources. I start with a little sample code: public class Tracer : IDisposable { bool disposed; FileStream fileStream; public Tracer() { //Some fileStream initialization } public void Dispose() { this.Dispose(true); GC.SuppressFinalize(this); } protected virtual void Dispose(bool disposing) { if (!disposed) { if (disposing) { if (fileStream != null) { fileStream.Dispose(); } } disposed = true; } } } public class ServiceWrapper : Tracer { bool disposed; ServiceHost serviceHost; //Some properties public ServiceWrapper () { //Some serviceHost initialization } //protected override void Dispose(bool disposing) //{ // if (!disposed) // { // if (disposing) // { // if (serviceHost != null) // { // serviceHost.Close(); // } // } // disposed = true; // } //} } My real question is: how to implement the disposable pattern inside my ServiceWrapper class to be sure that when I will dispose an instance of it, it will dispose resources in both inherited and base class? Thanks.

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  • SQL - when should you use "with (nolock)"

    - by Andy White
    Can someone explain the implications of using "with (nolock)" on queries, when you should/shouldn't use it? For example, if you have a banking application with high transaction rates and a lot of data in certain tables, in what types of queries would nolock be okay? Are there cases when you should always use it/never use it?

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  • Should I use a class in this: Reading a XML file using lxml.

    - by PulpFiction
    Hi everyone. This question is in continuation to my previous question, in which I asked about passing around an ElementTree. I need to read the XML files only and to solve this, I decided to create a global ElementTree and then parse it wherever required. My question is: Is this an acceptable practice? I heard global variables are bad. If I don't make it global, I was suggested to make a class. But do I really need to create a class? What benefits would I have from that approach. Note that I would be handling only one ElementTree instance per run, the operations are read-only. If I don't use a class, how and where do I declare that ElementTree so that it available globally? (Note that I would be importing this module) Please answer this question in the respect that I am a beginner to development, and at this stage I can't figure out whether to use a class or just go with the functional style programming approach.

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  • Tracking user changes in ASP.NET MVC

    - by Ian Roke
    I have a requirement to track what authenticated users change with regards to the data when logged in. I don't need to track what pages they look at although that could be very useful in future. I have thought about saving the User Guid but that seems very clunky. Are there other methods/best practises?

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  • Need help in sorting the programming buzz-words

    - by cwap
    How do you sort out the good buzz from the bad buzz? - I really need your help here :) I see a lot of buzz-words nowadays, both here on SO and in school. For example, we had a teacher who everyone respected, who said "be careful about gold-plating and death-by-interfacing". Now, everyone and their mama cries whenever I'm creating an interface.. Another example would be here on SO where lately "premature optimization is the root of all evil", so everytime someone asks a perfomance question, he'll get that sentence thrown in his face. A few months ago I remember it was all about NHibernate in here, etc., etc... These things comes and goes, but only the good buzz stays. Now, how do you seperate the good from the bad? By reading blogs from respected persons? By trying to come to a conclusion on your own, and then try to convince others that you're right? By simply ignoring it?

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  • My User control belonging to which Design Pattern??

    - by prashant
    Hello, I am creating a reusable component in C#.net. For that i have started a Control Library project and added a Control. Class MyControl : Control{} My user control just displays some images which will be used in many Windows Applications. Can you please tell me which design pattern i am using here. I am unable to decide which pattern they belongs. Thanks

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  • Correct approach to validate attributes of an instance of class

    - by systempuntoout
    Having a simple Python class like this: class Spam(object): __init__(self, description, value): self.description = description self.value = value Which is the correct approach to check these constraints: "description cannot be empty" "value must be greater than zero" Should i: 1.validate data before creating spam object ? 2.check data on __init__ method ? 3.create an is_valid method on Spam class and call it with spam.isValid() ? 4.create an is_valid static method on Spam class and call it with Spam.isValid(description, value) ? 5.check data on setters declaration ? 6.... Could you recommend a well designed\Pythonic\not verbose (on class with many attributes)\elegant approach?

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  • Problem understanding Inheritance

    - by dhruvbird
    I've been racking my brains over inheritance for a while now, but am still not completely able to get around it. For example, the other day I was thinking about relating an Infallible Human and a Fallible Human. Let's first define the two: Infallible Human: A human that can never make a mistake. It's do_task() method will never throw an exception Fallible Human: A human that will occasionally make a mistakes. It's do_task() method may occasionally throw a ErrorProcessingRequest Exception The question was: IS an infallible human A fallible human OR IS a fallible human AN infallible human? The very nice answer I received was in the form of a question (I love these since it gives me rules to answer future questions I may have). "Can you pass an infallible human where a fallible human is expected OR can you pass a fallible human where an infallible human is expected?" It seems apparent that you can pass an infallible human where a fallible human is expected, but not the other way around. I guess that answered my question. However, it still feels funny saying "An infallible human is a fallible human". Does anyone else feel queasy when they say it? It almost feels as if speaking out inheritance trees is like reading out statements from propositional calculus in plain English (the if/then implication connectives don't mean the same as that in spoken English). Does anyone else feel the same?

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  • What exactly is GRASP's Controller about?

    - by devoured elysium
    What is the idea behind Grasp's Controller pattern? My current interpretation is that sometimes you want to achieve something that needs to use a couple of classes but none of those classes could or has access to the information needed to do it, so you create a new class that does the job, having references to all the needed classes(this is, could be the information expert). Is this a correct view of what Grasp's Controller is about? Generally when googling or SO'ing controller, I just get results about MVC's (and whatnot) which are topics that I don't understand about, so I'd like answers that don't assume I know ASP.NET's MVC or something :( Thanks

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  • UI Design - design pattern for city/country drop down? (ASP.NET MVC)

    - by JK
    What is the best way to do a city/country dropdown pair in ASP.NET MVC? I see lots of places with country above city, but that's unnatural: in real life we write city/country. I've used city, then country, but the problem is that the user then has to go backwards after changing the country. The other problem is what do you do about cities/countries not in your list? If city/country are both drop downs, then the user cant type their own city if it is missing. But if you have a dropdown and a textbox, that makes it unwieldy (you end up with 4 controls to enter 2 pieces of data). Are there any examples websites where the city/country dropdown pair are done in a very useable and clear manner?

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  • Many-to-many relationship in oop

    - by Manu
    what is best way to model many-to-many relationship? lets say we have a two classes , Team and Player any given Player can be in multiple Team s any Team can have as many Player s as they like I like to call methods like playerX.getTeamList() to get the list of all the Team s he/she is in teamY.getPlayerList() to get the list of all the Player s in the team (or have some other way to do this effectively) I can think of two ways of doing this , but they just don't feels like good oop pattens. can you think of any good ways , perhaps a design patten ?

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  • When using out parameters in a function, is it good practice to initialize them in the function?

    - by adambox
    I have a function that uses out parameters to return multiple values to the caller. I would like to initialize them in the function, but I wasn't sure if that's a bad idea since you don't know when you call the function that it's going to change the values right away. The caller might assume that after the function returns, if whatever it was doing didn't work, the values would be whatever they were initialized to in the caller. Is it ok / good for me to initialize in the function? Example: public static void SomeFunction(int ixID, out string sSomething) { sSomething = ""; sSomething = something(ixID); if (sSomething = "") { somethingelse(); sSomething = "bar" } }

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  • Call a non member funcion on an instance before is constructed.

    - by Tom
    Hi everyone. I'm writing a class, and this doubt came up. Is this undef. behaviour? On the other hand, I'm not sure its recommended, or if its a good practice. Is it one if I ensure no exceptions to be thrown in the init function? //c.h class C{ float vx,vy; friend void init(C& c); public: C(); ~C(); }; //c.cpp C::C() { init(*this); } void init(C& c) //throws() to ensure no exceptions ? { c.vx = 0; c.vy = 0; } Thanks in advance

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  • Sequential coupling in code

    - by dotnetdev
    Hi, Is sequential coupling (http://en.wikipedia.org/wiki/Sequential_coupling) really a bad thing in code? Although it's an anti-pattern, the only risk I see is calling methods in the wrong order but documentation of an API/class library with this anti-pattern should take care of that. What other problems are there from code which is sequential? Also, this pattern could easily be fixed by using a facade it seems. Thanks

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  • When using Sessions is bad thing, and whats wrong with it?

    - by Amr ElGarhy
    I know that in community server which means that you can't use Sessions, and few years ago i remember i was working on a website where we were not allowed to use sessions. In my point of view sessions are a very helpful tool if we managed how to use the right way, but is using session variable in a website is something bad, when its bad and when its not?

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  • Can JavaScript be overused?

    - by ledhed2222
    Hello stackoverflow, I'm a "long time reader first time poster", glad to start participating in this forum. My experience is with Java, Python, and several audio programming languages; I'm quite new to the big bad web technologies: HTML/CSS/JavaScript. I'm making two personal sites right now and am wondering if I'm relying on JavaScript too much. I'm making a site where all pages have a bit of markup in common--stuff like the nav bar and some sliced background images--so I thought I'd make a pageInit() function to insert the majority of the HTML for me. This way if I make a change later, I just change the script rather than all the pages. I figure if users are paranoid enough to have JavaScript turned off, I'll give them an alert or something. Is this bad practice? Can JavaScript be overused? Thanks in advance.

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  • list all files from directories and subdirectories in Java

    - by Adnan
    What would be the fastest way to list the names of files from 1000+ directories and sub-directories? EDIT; The current code I use is: import java.io.File; public class DirectoryReader { static int spc_count=-1; static void Process(File aFile) { spc_count++; String spcs = ""; for (int i = 0; i < spc_count; i++) spcs += " "; if(aFile.isFile()) System.out.println(spcs + "[FILE] " + aFile.getName()); else if (aFile.isDirectory()) { System.out.println(spcs + "[DIR] " + aFile.getName()); File[] listOfFiles = aFile.listFiles(); if(listOfFiles!=null) { for (int i = 0; i < listOfFiles.length; i++) Process(listOfFiles[i]); } else { System.out.println(spcs + " [ACCESS DENIED]"); } } spc_count--; } public static void main(String[] args) { String nam = "D:/"; File aFile = new File(nam); Process(aFile); } }

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  • Am i using too much jquery? When i'm crossing the line?

    - by Andrea
    Lately i find myself using jquery and javascript a lot, often to do the same things that i did before using css. For example, i alternate table rows color or create buttons and links hover effects using javascript/jquery. Is this acceptable? Or should i keep using css for these kind of things? So the real question is: When i'm using too much jquery? How can i understand when i'm crossing the line? Thanks.

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  • Assignment in conditional operator

    - by DuoSRX
    I've seen a lot this kind of code recently : if ($foo = $bar->getFoo()) { baz($foo); } Is this considered good or bad practice ? For example, Netbeans IDE give a notice if you use this kind of code : Possible accidental assignment, assignments in conditions should be avoided What do you think ?

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