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  • What's the preferred way to use helper methods in Ruby?

    - by DR
    Disclaimer: Although I'm asking in context of a Rails application, I'm not talking about Rails helpers (i.e. view helpers) Let's say I have a helper method/function: def dispatch_job(job = {}) #Do something end Now I want to use this from several places (mostly controllers, but also a few BackgrounDRb workers) What's the preferred way to do this? I can think of two possibilities: 1. Use a class and make the helper a static method: class MyHelper def self.dispatch_job(job = {}) end end class MyWorker def run MyHelper.dispatch_job(...) end end 2. Use a module and include the method into whatever class I need this functionality module MyHelper def self.dispatch_job(job = {}) end end class MyWorker include MyHelper def run dispatch_job(...) end end 3. Other possibilities I don't know yet ... The first one is more Java-like, but I'm not sure if the second one is really an appropriate use of Ruby's modules.

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  • Can someone help with big O notation?

    - by Dann
    void printScientificNotation(double value, int powerOfTen) { if (value >= 1.0 && value < 10.0) { System.out.println(value + " x 10^" + powerOfTen); } else if (value < 1.0) { printScientificNotation(value * 10, powerOfTen - 1); } else // value >= 10.0 { printScientificNotation(value / 10, powerOfTen + 1); } } I understand how the method goes but I cannot figure out a way to represent the method. For example, if value was 0.00000009 or 9e-8, the method will call on printScientificNotation(value * 10, powerOfTen - 1); eight times and System.out.println(value + " x 10^" + powerOfTen); once. So the it is called recursively by the exponent for e. But how do I represent this by big O notation? Thanks!

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  • Factorial function - design and test.

    - by lukas
    I'm trying to nail down some interview questions, so I stared with a simple one. Design the factorial function. This function is a leaf (no dependencies - easly testable), so I made it static inside the helper class. public static class MathHelper { public static int Factorial(int n) { Debug.Assert(n >= 0); if (n < 0) { throw new ArgumentException("n cannot be lower that 0"); } Debug.Assert(n <= 12); if (n > 12) { throw new OverflowException("Overflow occurs above 12 factorial"); } //by definition if (n == 0) { return 1; } int factorialOfN = 1; for (int i = 1; i <= n; ++i) { //checked //{ factorialOfN *= i; //} } return factorialOfN; } } Testing: [TestMethod] [ExpectedException(typeof(OverflowException))] public void Overflow() { int temp = FactorialHelper.MathHelper.Factorial(40); } [TestMethod] public void ZeroTest() { int factorialOfZero = FactorialHelper.MathHelper.Factorial(0); Assert.AreEqual(1, factorialOfZero); } [TestMethod] public void FactorialOf5() { int factOf5 = FactorialHelper.MathHelper.Factorial(5); Assert.AreEqual(120,factOf5); } [TestMethod] [ExpectedException(typeof(ArgumentException))] public void NegativeTest() { int factOfMinus5 = FactorialHelper.MathHelper.Factorial(-5); } I have a few questions: Is it correct? (I hope so ;) ) Does it throw right exceptions? Should I use checked context or this trick ( n 12 ) is ok? Is it better to use uint istead of checking for negative values? Future improving: Overload for long, decimal, BigInteger or maybe generic method? Thank you

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  • Synchronizing access to an inner object's methods?

    - by user291701
    Suppose I have the following: public class Foo { private ReadingList mReadingList = new ReadingList(); public ReadingList getReadingList() { synchronized (mReadingList) { return mReadingList; } } } If I try modifying the ReadingList object in two threads, the synchronization above won't help me, right?: // Thread 1 foo1.getReadingList().setName("aaa"); // Thread 2 foo2.getReadingList().setName("bbb"); do I have to wrap each method I want synchronized like so: public class Foo { private ReadingList mReadingList = new ReadingList(); public synchronized void setReadingListName(String name) { mReadingList.setName(name); } public synchronized void setReadingListAuthor(String author) { mReadingList.setAuthor(author); } ... and so on for each method of ReadingList I want exposed and synched? I'd end up just writing wrapper methods for each method of ReadingList. Thanks

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  • Run code before class instanciation in ActionScript 3

    - by soow.fr
    I need to run code in a class declaration before its instanciation. This would be especially useful to automatically register classes in a factory. See: // Main.as public class Main extends Sprite { public function Main() : void { var o : Object = Factory.make(42); } } // Factory.as public class Factory { private static var _factory : Array = new Array(); public static function registerClass(id : uint, c : Class) : void { _factory[id] = function () : Object { return new c(); }; } public static function make(id : uint) : Object { return _factory[id](); } } // Foo.as public class Foo { // Run this code before instanciating Foo! Factory.registerClass(42, Foo); } AFAIK, the JIT machine for the ActionScript language won't let me do that since no reference to Foo is made in the Main method. The Foo class being generated, I can't (and don't want to) register the classes in Main: I'd like to register all the exported classes in a specific package (or library). Ideally, this would be done through package introspection, which doesn't exist in ActionScript 3. Do you know any fix (or other solution) to my design issue?

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  • looking for a good vc++ profiler, already checked previous posts

    - by coreSOLO
    I'm looking for a good profiler for vs2008 professional edition, free or reasonably priced. I've already checked previous posts and tried about 8 profilers, but most of them are too basic or too detailed. Kindly suggest something, my requirements are as follows: It can be compiled, so that its well integrated with my application. I'm not shying away from instrumenting my methods. The output should be simple, i only need call count and time taken by methods and nothing else. I am mostly concerned about things INSIDE a method, you may call it line by line profiling. I want to select a method and know which line (expression / method call) is eating most of the time.

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  • Performance problem loading lots of user controls

    - by codymanix
    My application is loading a bunch of the same user control into a ScrollPanel. The problem is, this is very slow. The profiler show that the method Application.LoadComponent(), which is called internally by in the designer code in the constructor of my user control, is the bottleneck. The documentation of this method says, that this method load XAML files. I alway though the compiler compiles XAML to BAML and embedds it into the assembly. So the question is, how can I use BAML instead of XAML? Is there another way to make loading my user controls faster?

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  • Preallocating memory with C++ in realtime environment

    - by Elazar Leibovich
    I'm having a function which gets an input buffer of n bytes, and needs an auxillary buffer of n bytes in order to process the given input buffer. (I know vector is allocating memory at runtime, let's say that I'm using a vector which uses static preallocated memory. Imagine this is NOT an STL vector.) The usual approach is void processData(vector<T> &vec) { vector<T> &aux = new vector<T>(vec.size()); //dynamically allocate memory // process data } //usage: processData(v) Since I'm working in a real time environment, I wish to preallocate all the memory I'll ever need in advance. The buffer is allocated only once at startup. I want that whenever I'm allocating a vector, I'll automatically allocate auxillary buffer for my processData function. I can do something similar with a template function static void _processData(vector<T> &vec,vector<T> &aux) { // process data } template<size_t sz> void processData(vector<T> &vec) { static aux_buffer[sz]; vector aux(vec.size(),aux_buffer); // use aux_buffer for the vector _processData(vec,aux); } // usage: processData<V_MAX_SIZE>(v); However working alot with templates is not much fun (now let's recompile everything since I changed a comment!), and it forces me to do some bookkeeping whenever I use this function. Are there any nicer designs around this problem?

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  • how can access public properties of MasterPage from external Class ?

    - by eugeneK
    Why i can't access MasterPage's public property (MessagePlaceholder) from other Class (Errors) ? Error compiler gives me is "Error 1 The type or namespace name 'MyMasterPage' could not be found (are you missing a using directive or an assembly reference?)" my master page code behind using System; using System.Collections.Generic; using System.Linq; using System.Web; using System.Web.UI; using System.Web.UI.WebControls; public partial class MyMasterPage : System.Web.UI.MasterPage { public string MessagePlaceholder { get { return messagePlaceholder.InnerHtml; } set { messagePlaceholder.InnerHtml = value; } } protected void Page_Load(object sender, EventArgs e) { if (!IsPostBack) { messagePlaceholder.InnerHtml = Errors.getMessage(); } } } my Errors Class public static string getMessage() { HttpContext c = HttpContext.Current; string messageType = ""; if (c.Session["errorMessage"] != null) { messageType = "errorMessage"; } else if (c.Session["successMessage"] != null) { messageType = "successMessage"; } if (!string.IsNullOrEmpty(messageType)) { StringBuilder userMessageSb = new StringBuilder(); userMessageSb.Append(string.Format("<div id=\"{0}\" title=\"{1}\">{2}</div>", messageType, messageType.Replace("Message",string.Empty), c.Session[messageType])); // fix so message will not re-appear c.Session.Remove(messageType); messageType = userMessageSb.ToString(); } return messageType; } public static void setSuccess(string successMessage, bool isRedirect) { HttpContext.Current.Session["successMessage"] = successMessage; } public static void setError(string errorMessage, bool isRedirect) { HttpContext.Current.Session["errorMessage"] = errorMessage; if (!isRedirect) { ((HttpContext.Current.CurrentHandler as System.Web.UI.Page).Master as MyMasterPage).MessagePlaceholder = getMessage(); } } this is how i set error if (true) { Errors.setError("this is an error demo", false); return; } or with redirect after error if (true) { Errors.setError("yet another error", true); Response.Redirect("~/error.aspx"); }

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  • Automatically mount partition when needed

    - by David Parunakian
    Hello, Can anyone suggest a method of mounting a partition (e.g. an NFS share) when a user changes into the directory it is set to be mounted to, and not on the system startup? So far I've been unable to propose such a method, aside from editing BASH built-in cd implementation and forcing an fstab/mtab check before the working directory is actually changed.

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  • Transaction within transaction

    - by user281521
    Hello, I want to know if open a transaction inside another is safe and encouraged? I have a method: def foo(): session.begin try: stuffs except Exception, e: session.rollback() raise e session.commit() and a method that calls the first one, inside a transaction: def bar(): stuffs try: foo() #<<<< there it is :) stuffs except Exception, e: session.rollback() raise e session.commit() if I get and exception on the foo method, all the operations will be rolled back? and everything else will work just fine? thanks!!

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  • Right design to validate attributes of a class instance

    - 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? 6.... Could you recommend a well designed\Pythonic\not verbose (on class with many attributes)\elegant approach?

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  • Get back the changes after accidental checkout?

    - by Millisami
    The following was the status of my repo. [~/rails_apps/jekyll_apps/nepalonrails (design)?] ? gst # On branch design # Changed but not updated: # (use "git add/rm <file>..." to update what will be committed) # (use "git checkout -- <file>..." to discard changes in working directory) # # modified: _layouts/default.html # deleted: _site/blog/2010/04/07/welcome-to-niraj-blog/index.html # deleted: _site/blog/2010/04/08/the-code-syntax-highlight/index.html # deleted: _site/blog/2010/05/01/showing-demo-to-kalyan/index.html # deleted: _site/config.ru # deleted: _site/index.html # deleted: _site/static/css/style.css # deleted: _site/static/css/syntax.css # modified: static/css/style.css # no changes added to commit (use "git add" and/or "git commit -a") Accedently, I did git checkout -f and now the changes are gone which I wasnt supposed to do. [~/rails_apps/jekyll_apps/nepalonrails (design)?] ? git co -f [~/rails_apps/jekyll_apps/nepalonrails (design)] ? gst # On branch design nothing to commit (working directory clean) [~/rails_apps/jekyll_apps/nepalonrails (design)] ? Can I get back the changes back?

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  • Servlet's doGet not called from JSP form

    - by RadnaOdela
    I have this code on my JSP page <form action="LoginServlet" method="get"> <input type="text" name="username" /> <input type="text" name="password" /> <input type="submit" value="Submit" /> </form> and when I press Submit I get: The page cannot be displayed The page you are looking for is currently unavailable. The Web site might be experiencing technical difficulties, or you may need to adjust your browser settings. and LoginServlet.doGet method doesn't get called. But then when I press Enter again (in address bar) my doGet method gets called. What is wrong? I am using JEE eclipse and Tomcat

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  • When is a try catch not a try catch?

    - by Dearmash
    I have a fun issue where during application shutdown, try / catch blocks are being seemingly ignored in the stack. I don't have a working test project (yet due to deadline, otherwise I'd totally try to repro this), but consider the following code snippet. public static string RunAndPossiblyThrow(int index, bool doThrow) { try { return Run(index); } catch(ApplicationException e) { if(doThrow) throw; } return ""; } public static string Run(int index) { if(_store.Contains(index)) return _store[index]; throw new ApplicationException("index not found"); } public static string RunAndIgnoreThrow(int index) { try { return Run(index); } catch(ApplicationException e) { } return ""; } During runtime this pattern works famously. We get legacy support for code that relies on exceptions for program control (bad) and we get to move forward and slowly remove exceptions used for program control. However, when shutting down our UI, we see an exception thrown from "Run" even though "doThrow" is false for ALL current uses of "RunAndPossiblyThrow". I've even gone so far as to verify this by modifying code to look like "RunAndIgnoreThrow" and I'll still get a crash post UI shutdown. Mr. Eric Lippert, I read your blog daily, I'd sure love to hear it's some known bug and I'm not going crazy. EDIT This is multi-threaded, and I've verified all objects are not modified while being accessed

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  • Deserialising Json to derived types in Asp.Net Web API

    - by IoChaos
    I'm calling a method of my WebAPI sending a json that I would like to match (or bind) with a model. In the controller I have a method like: public Result Post([ModelBinder(typeof(CustomModelBinder))]MyClass model); 'MyClass', wich is given as a parameter is an abstract class. I would like that at, depending of the type of json passed, the correct inherited class is instantiated. To achieve it, I'm trying to implement a custom binder. The problem is that (I don't know if it's very basic but I can't find anything) I don't know how to retrieve the raw Json (or better, some kind of serialization) that comes in the request. I see: actionContext.Request.Content But all methods are exposed as async. I don't know who this fits with passing the generate model to the controller method... Thanks a lot!

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  • How do I disable Aero transparency in Firefox 4?

    - by Titus
    I noticed that the transparent interface in Firefox 4 for Windows 7 is really curbing performance. After Googling for a method to disable Aero for Firefox, however, I got no results. There just doesn't seem to be a straight forward (such as a simple Boolean to turn it off in about:config) method to get rid of Aero effects. Is it even possible in the Firefox 4 beta? I'm using Firefox 4 beta 12 (soon to be beta 13 after the update).

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  • $(ajax) using webservice response

    - by loviji
    Hello, I have a simple ajax query. $(document).ready(function () { var infManipulate = true; var tableID=<%=TableID %>; var userName="<%=CurrentUserName%>"; $.ajax({ type: "POST", url: "../../WS/Permission.asmx/CanManipulate", data: "tableID=" + tableID + "&userName=" + userName + "", success: function (msg) { //**how can I know there method CanManipulate returned true or false?** msg; debugger; }, error: function (msg) { } }); And simple web-method [WebMethod] public bool CanManipulate(int tableID, string userName) { //some op. return prm.haveThisMatch(userName, tableID, "InfManipulate"); } how can I know there method CanManipulate returned true or false value in $(ajax) content?

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  • Rails: How do I run a before_save only if certain conditions are met?

    - by Shpigford
    I have a before_save method that I call that renames an uploaded image. before_save :randomize_file_name def randomize_file_name extension = File.extname(screen_file_name).downcase key = ActiveSupport::SecureRandom.hex(8) self.screen.instance_write(:file_name, "#{key}#{extension}") end That method is part of my Item model. That works great when I create a new item or need to update the image associated with an item...but the problem is that if I need to update an item but NOT the image, the randomize_file_name method still gets run and renames the file in the database (though not the file itself, obviously). So, I'm thinking I need to figure out a way to only run randomize_file_name if a file is included in the form submission...but I'm not sure how to pull that off.

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  • gwt - Using List<Serializable> in a RPC call?

    - by Garagos
    I have a RPC service with the following method: public List<Serializable> myMethod(TransactionCall call) {...} But I get a warning when this method is analyzed, and then the rpc call fails Analyzing 'my.project.package.myService' for serializable types Analyzing methods: public abstract java.util.List<java.io.Serializable> myMethod(my.project.package.TransactionCall call) Return type: java.util.List<java.io.Serializable> [...] java.io.Serializable Verifying instantiability (!) Checking all subtypes of Object wich qualify for serialization It seems I can't use Serializable for my List... I could use my own interface instead (something like AsyncDataInterface, wich implements the Serializable interface) but the fact is that my method will return a list custom objects AND basic objects (such as Strings, int....). So my questions are: Is it a standart behaviour? (I can't figure out why I can't use this interface in that case) Does anyone have a workaround for that kind of situation?

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  • FormStartPosition.CenterParent does not work

    - by kol
    In the following code, only the second method works for me (.NET 4.0). FormStartPosition.CenterParent does not center the child form over its parent. Why? Source: this SO question using System; using System.Drawing; using System.Windows.Forms; class Program { private static Form f1; public static void Main() { f1 = new Form() { Width = 640, Height = 480 }; f1.MouseClick += f1_MouseClick; Application.Run(f1); } static void f1_MouseClick(object sender, MouseEventArgs e) { Form f2 = new Form() { Width = 400, Height = 300 }; switch (e.Button) { case MouseButtons.Left: { // 1st method f2.StartPosition = FormStartPosition.CenterParent; break; } case MouseButtons.Right: { // 2nd method f2.StartPosition = FormStartPosition.Manual; f2.Location = new Point( f1.Location.X + (f1.Width - f2.Width) / 2, f1.Location.Y + (f1.Height - f2.Height) / 2 ); break; } } f2.Show(f1); } }

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  • iphone singleton object synchronization

    - by user127091
    I'm working on an iphone app but this is probably a general question. I have a singleton Model class and there would be scenarios where multiple NSOperations (threads) would exist and work with the singleton object. If they all call the same method in this object, do i need to have some locking mechanism? Or can this method be executed only one at a time? I do not have a computer science background but my guess is that all threads would have their CALL to the same address (this method). Also can you please suggest a good beginner programming book that discusses general programming concepts. I don't have the brains for Knuth kinda books.

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  • OO C++ - Virtual Methods

    - by Phorce
    Just a really quick question here. I'm using virtual functions to read in from a text file. Now, it's virtual because in one aspect I want the values to be normalised, and, in the other respect I don't want them to be normalised. I have tried to do this: bool readwav(string theFile, 'native'); So in theory, if the 'native' is used, this method should be called, however, if 'double' is called then a different version of the method is called. Same for if the value is empty, it should just perform the native option. First question, why doesn't the declaration above work? Also, is this the best route to go down? Or, would it be better to have just one class method that switches between the options. Thanks :)

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  • Where is the best place to call the .tolist(); inside my controller classes or inside my model repository classes

    - by john G
    I have the following action method, inside my asp.net mvc web application:- public JsonResult LoadZoneByDataCenter(string id) { var zonelist = repository.getrealtedzone(Convert.ToInt32(id)).ToList(); //code goes here Which calls the following model repository method:- public IQueryable<Zone> getrealtedzone(int? dcid) { return tms.Zones.Where(a=> a.DataCenterID == dcid || dcid == null); } Currently I am calling the .tolist() which will interpret the Database from my action method, but my question is where is the best place to call the .tolist() inside the controller or inside the model classes and why ? thanks

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  • Should I be using abstract methods in this Python scenario?

    - by sfjedi
    I'm not sure my approach is good design and I'm hoping I can get a tip. I'm thinking somewhere along the lines of an abstract method, but in this case I want the method to be optional. This is how I'm doing it now... from pymel.core import * class A(object): def __init__(self, *args, **kwargs): if callable(self.createDrivers): self._drivers = self.createDrivers(*args, **kwargs) select(self._drivers) class B(A): def createDrivers(self, *args, **kwargs): c1 = circle(sweep=270)[0] c2 = circle(sweep=180)[0] return c1, c2 b = B() In the above example, I'm just creating 2 circle arcs in PyMEL for Maya, but I fully intend on creating more subclasses that may or may not have a createDrivers method at all! So I want it to be optional and I'm wondering if my approach is—well, if my approach could be improved?

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