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  • What comes first in Ruby's object model?

    - by Timothy
    I've been reading Metaprogramming Ruby and the object model like the chicken or egg dilemma. In Ruby 1.8, the Object class is an instance of Class. Module's superclass is Object and is an instance of Class. Class' superclass is Module, and it is an instance of Class (self-referential). Say class SomeClass; end is defined somewhere; SomeClass is an instance of Class, however its superclass is Object. Why does an instance of Class have Object as the superclass instead of nil? Also, if Object is to exist, then Class has to exist, but then Module has to exist, but for Module to exist Object has to exist. How are these classes created?

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  • Can we create a class from a xml file ?

    - by panzerschreck
    Hello, Is it possible to create a class dynamically by reading an xml file ( in java preferably) ? if yes, please provide pointers on how to do it. In the process of development, we have come up with a class that has 5 attributes, all these attributes correspond to an entry in the xml file, now if the user adds/modifies the xml entry the object corresponding to it must change automatically, one approach would be generate the source code, before compile time.Is there any other way ? Is there any common pattern to model such changes in the system ? Thanks,

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  • Generic class for performing mass-parallel queries. Feedback?

    - by Aaron
    I don't understand why, but there appears to be no mechanism in the client library for performing many queries in parallel for Windows Azure Table Storage. I've created a template class that can be used to save considerable time, and you're welcome to use it however you wish. I would appreciate however, if you could pick it apart, and provide feedback on how to improve this class. public class AsyncDataQuery<T> where T: new() { public AsyncDataQuery(bool preserve_order) { m_preserve_order = preserve_order; this.Queries = new List<CloudTableQuery<T>>(1000); } public void AddQuery(IQueryable<T> query) { var data_query = (DataServiceQuery<T>)query; var uri = data_query.RequestUri; // required this.Queries.Add(new CloudTableQuery<T>(data_query)); } /// <summary> /// Blocking but still optimized. /// </summary> public List<T> Execute() { this.BeginAsync(); return this.EndAsync(); } public void BeginAsync() { if (m_preserve_order == true) { this.Items = new List<T>(Queries.Count); for (var i = 0; i < Queries.Count; i++) { this.Items.Add(new T()); } } else { this.Items = new List<T>(Queries.Count * 2); } m_wait = new ManualResetEvent(false); for (var i = 0; i < Queries.Count; i++) { var query = Queries[i]; query.BeginExecuteSegmented(callback, i); } } public List<T> EndAsync() { m_wait.WaitOne(); return this.Items; } private List<T> Items { get; set; } private List<CloudTableQuery<T>> Queries { get; set; } private bool m_preserve_order; private ManualResetEvent m_wait; private int m_completed = 0; private void callback(IAsyncResult ar) { int i = (int)ar.AsyncState; CloudTableQuery<T> query = Queries[i]; var response = query.EndExecuteSegmented(ar); if (m_preserve_order == true) { // preserve ordering only supports one result per query this.Items[i] = response.Results.First(); } else { // add any number of items this.Items.AddRange(response.Results); } if (response.HasMoreResults == true) { // more data to pull query.BeginExecuteSegmented(response.ContinuationToken, callback, i); return; } m_completed = Interlocked.Increment(ref m_completed); if (m_completed == Queries.Count) { m_wait.Set(); } } }

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  • Java: how to have global values inside a class?

    - by HH
    I want less methods. I want a common global TestClass from which I could use any of its value inside the class. import java.util.*; import java.io.*; public class TestClass { TestClass(String hello){ String hallo = hello; String halloSecond = "Saluto!"; } public static void main(String[] args) { TestClass test = new TestClass("Tjena!"); System.out.println("I want "Tjena!": " + test.hallo); TestClass testSecond = new TestClass("1"); System.out.println("I want Saluto!:" + test.halloSecond); System.out.println("I want Saluto!:" + testSecond.halloSecond); // How can I get glob.vars like the "Saluto!"? } }

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  • CSS selectors : should I minimise my use of the class attribute in the HTML or optimise the speed

    - by Laurent Bourgault-Roy
    As I was working on a small website, I decided to use the PageSpeed extension to check if their was some improvement I could do to make the site load faster. However I was quite surprise when it told me that my use of CSS selector was "inefficient". I was always told that you should keep the usage of the class attribute in the HTML to a minimum, but if I understand correctly what PageSpeed tell me, it's much more efficient for the browser to match directly against a class name. It make sense to me, but it also mean that I need to put more CSS classes in my HTML. It also make my .css file a little harder to read. I usually tend to mark my CSS like this : #mainContent p.productDescription em.priceTag { ... } Which make it easy to read : I know this will affect the main content and that it affect something in a paragraph tag (so I wont start to put all sort of layout code in it) that describe a product and its something that need emphasis. However it seem I should rewrite it as .priceTag { ... } Which remove all context information about the style. And if I want to use differently formatted price tag (for example, one in a list on the sidebar and one in a paragraph), I need to use something like that .paragraphPriceTag { ... } .listPriceTag { ... } Which really annoy me since I seem to duplicate the semantic of the HTML in my classes. And that mean I can't put common style in an unqualified .priceTag { ... } and thus I need to replicate the style in both CSS rule, making it harder to make change. (Altough for that I could use multiple class selector, but IE6 dont support them) I believe making code harder to read for the sake of speed has never been really considered a very good practice . Except where it is critical, of course. This is why people use PHP/Ruby/C# etc. instead of C/assembly to code their site. It's easier to write and debug. So I was wondering if I should stick with few CSS classes and complex selector or if I should go the optimisation route and remove my fancy CSS selectors for the sake of speed? Does PageSpeed make over the top recommandation? On most modern computer, will it even make a difference?

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  • mootools 1.1.1 scrollto element with class name ... anything like jquery?

    - by dtour
    I get the impression mootools will do this, but in a roundabout way. I am working with livevalidation script. What I want to achieve is when the from runs and errors are generated then the page will scroll to the first error found. This will be outputted as: <span class=" LV_validation_message LV_invalid">Can't be empty!</span> with jquery I could do the following: $.scrollTo($('span.LV_invalid:1')); I get the feeling in mootools I have to first find the position of the first span with class LV_invalid then pass this to the scrollTo function or is there a much simpler solution?

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  • Is it possible to apply inheritance to a Singleton class?

    - by Bragaadeesh
    Hi, Today I faced one question in interview. Is it possible to apply inheritance concept on Singleton Classes. I said since the constructor is private, we cannot extend that Singleton class (can someone please validate this). Next thing he asked me is to apply inheritance on that Singleton class. So, I made the Singleton's constructor as protected thinking that child's constructor also has be protected. But I was wrong the child can have a modifier either equal to or higher than that. So, I asked him to give a real world example on such a case. He was not able to give me one and said that I cant ask questions and wanted me to tell whether this scenario is possible or not. I went kind of blank. My question here is, Is this possible? Even if its possible, what is the use of it? What real world scenario would demand such a use. Thanks

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  • What could possibly cause this error when declaring an object inside a class?

    - by M4design
    I'm battling with this assignment :) I've got two classes: Ocean and Grid. When I declare an object of the Grid inside the Ocean: unsigned int sharkCount; Grid grid; The compiler/complainer says: error C2146: syntax error : missing ';' before identifier 'grid' Can you possibly predict what produces this error with the limited info I provided? It seems that as if the Ocean doesn't like the Grid class. Could this be because of the poor implementation of the grid class. BTW the Grid has a default constructor. Yet the error happens in compiling time!. EDIT: They're each in separate header file, and I've included the Grid.h in the Ocean.h.

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  • how to import Java class with Python using Eclipse?

    - by JChao
    Hi, I'm trying to write Jython where the Python file imports classes from Java I'm using Eclipse with PyDev. My Python code looks like: from eclipsejavatest import eclipseJavaTest from eclipsejavatest import JavaClass class eclipsePyPrint(eclipseJavaTest): def eclipsepyMain(self): print "python main method" eclipseJavaTest.printerCount(4) print eclipseJavaTest.gotoPython() eclipseJavaTest.printerSentence() samplepyClass = JavaClass("Jython plain") samplepyClass.setName("jython fancy") print samplepyClass.getName() but I'm getting the error ImportError: No module named eclipsejavatest The Python project references the Java project. I've tried exporting the Java project and adding the .jar to the Jython Class Path for the Python project. I'm not sure what to do to get this to work.

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  • jquery :last missing multiple classes

    - by mickyjtwin
    I have an unordered list, and am using jquery to find the last ul and apply a class. jQuery("ul.class1:last").addClass("lastUi"); The html is as follows: <ul class="class1"></ul> <ul class="class1"></ul> This is working fine, however it has now changed in that another class is being added to the list so the html looks like: <ul class="class1"></ul> <ul class="class1 class2"></ul> <ul class="class1"></ul> <ul class="class1 class2"></ul> The jQuery code is now not picking up the last ul with both class1 and class2 as the last element and isn't adding the lastUI class.

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  • Pointer to a C++ class member function as a global function's parameter?

    - by marcin1400
    I have got a problem with calling a global function, which takes a pointer to a function as a parameter. Here is the declaration of the global function: int lmdif ( minpack_func_mn fcn, void *p, int m, int n, double *x, double *fvec, double ftol) The "minpack_func_mn" symbol is a typedef for a pointer to a function, defined as: typedef int (*minpack_func_mn)(void *p, int m, int n, const double *x, double *fvec, int iflag ); I want to call the "lmdif" function with a pointer to a function which is a member of a class I created, and here is the declaration of this class function: int LT_Calibrator::fcn(void *p, int m, int n, const double *x, double *fvec,int iflag) I am calling a global function like this: info=lmdif(&LT_Calibrator::fcn, 0, m, n, x, fvec, ftol) Unfortunately, I get a compiler error, which says: "error C2664: 'lmdif' : cannot convert parameter 1 from 'int (__thiscall LT_Calibrator::* )(void *,int,int,const double *,double *,int)' to 'minpack_func_mn' 1 There is no context in which this conversion is possible" Is there any way to solve that problem?

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  • Is there a standard .NET exception to throw when a class doesn't implement a required attribute?

    - by a typing monkey
    Suppose I want to throw a new exception when invoking a generic method with a type that doesn't have a required attribute. Is there a .NET exception that's appropriate for this situation, or, more likely, one that would be a suitable ancestor for a custom exception? For example: public static class ClassA { public static T DoSomething<T>(string p) { Type returnType = typeof(T); object[] typeAttributes = returnType.GetCustomAttributes(typeof(SerializableAttribute), true); if ((typeAttributes == null) || (typeAttributes.Length == 0)) { // Is there an exception type in the framework that I should use/inherit from here? throw new Exception("This class doesn't support blah blah blah"); // Maybe ArgumentException? That doesn't seem to fit right. } } } Thanks.

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  • Is it possible to override a property and return a derived type in VB.NET?

    - by Casey
    Consider the following classes representing an Ordering system: Public Class OrderBase Public MustOverride Property OrderItem() as OrderItemBase End Class Public Class OrderItemBase End Class Now, suppose we want to extend these classes to a more specific set of order classes, keeping the aggregate nature of OrderBase: Public Class WebOrder Inherits OrderBase Public Overrides Property OrderItem() as WebOrderItem End Property End Class Public Class WebOrderItem Inherits OrderItemBase End Class The Overriden property in the WebOrder class will cause an error stating that the return type is different from that defined in OrderBase... however, the return type is a subclass of the type defined in OrderBase. Why won't VB allow this?

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  • Is is possible to intercept a constructor on a class you do not own?

    - by code poet
    Referring to my possible answer to this question: http://stackoverflow.com/questions/2907535/how-would-you-audit-asp-net-membership-tables-while-recording-what-user-made-the/2911616#2911616 Is it possible to intercept a call, coming from code you do not own, to a ctor on a sealed internal class that you do not own with the intention of manipulating the object before returning? Concrete example: SqlMembershipProvider, for all of it's data access, instantiates a connection helper class, System.Web.DataAccess.SqlConnectionHolder. The desired result is to intercept this instantiation and perform an operation on the public connection that is opened in the ctor of System.Web.DataAccess.SqlConnectionHolder before letting execution continue. Is this possible. If so, an brief example would be appreciated.

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  • How to optimize 'class name' in Android XML Layout ?

    - by Mac
    Hello, I am using some custom components in my project for that I am using following code. <view class="com.android.mypackage.myclass" id="@+id/button" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@android:drawable/button" android:padding="10dip" /> Its working perfectly fine, I am using this code near about 35 times in my application. so while creating new clone application from same project, I need to update package name in 35 places. Is there any way to reduce these efforts? I had tried with "class="@string/class_name" but its not working.

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  • How do I indicate that a class doesn't support certain operators?

    - by romeovs
    I'm writing a class that represents an ordinal scale, but has no logical zero-point (eg time). This scale should permit addition and substraction (operator+, operator+=, ...) but not multiplication. Yet, I always felt it to be a good practice that when one overloads one operator of a certain group (in this case the math operators), one should also overload all the others that belong to that group. In this case that would mean I should need to overload the multiplication and division operators also, because if a user can use A+B he would probable expect to be able the other operators. Is there a method that I can use to throw an error for this at compiler time? The easiest method would be just no to overload the operators operator*, ... yet it would seem appropriate to add a bit more explaination than operator* is not know for class "time". Or is this something that I really should not care about (RTFM user)?

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  • Editing/Modifying a .java file programmatically? (not the .class file)

    - by Jay
    So, here is a piece of code using CodeModel that generates java code: JCodeModel cm = new JCodeModel(); JDefinedClass dc = cm._class("foo.Bar"); JMethod m = dc.method(0, int.class, "foo"); m.body()._return(JExpr.lit(5)); File f = new File("C:/target/classes"); f.mkdirs(); cm.build(f); This code generates a .java file: package foo; public class Bar { int foo() { return 5; } } However, I DO NOT want CodeModel to create a new java file for me. I do have a .java file already and would like to add a few lines of code to a method inside it. So, I would like the API to modify the java file directly/ create a modified copy of it. Is there a way to doing this?

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  • how to access a label form user control in Parent class ?

    - by haansi
    I have a class UserControlBase that inherits System.Web.UI.UserControl and my user controls inherit UserControlBase class. UserControlBase has some common functions that are used in all user controls. I want to put error display funtion to UserControlBase as well so that I may not have to declare and manage it in all user controls. Error will be displayed in some label in usercontrol. Issue is how to access label which is in usercontrol in UserControlBase in function ? I dont want to pass label as argument. Please guide me on this issue. thanks

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  • How to solve Only Web services with a [ScriptService] attribute on the class definition can be called from script

    - by NevenHuynh
    I attempt to use webservice return POCO class generated from entity data model as JSON when using Jquery AJAX call method in webservice. but I have problem with error "Only Web services with a [ScriptService] attribute on the class definition can be called from script", and getting stuck in it, Here is my code : namespace CarCareCenter.Web.Admin.Services { /// <summary> /// Summary description for About /// </summary> [WebService(Namespace = "http://tempuri.org/")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] [System.ComponentModel.ToolboxItem(false)] // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. // [System.Web.Script.Services.ScriptService] public class About : System.Web.Services.WebService { [ScriptMethod(ResponseFormat = ResponseFormat.Json)] [WebMethod] public static Entities.Category getAbout() { Entities.Category about = new Entities.Category(); using (var context = new CarCareCenterDataEntities()) { about = (from c in context.Categories where c.Type == "About" select c).SingleOrDefault(); } return about; } } } aspx page : <script type="text/javascript"> $(document).ready(function () { $.ajax({ type: 'POST', dataType: 'json', contentType: 'application/json; charset=utf-8', url: '/Services/About.asmx/getAbout', data: '{}', success: function (response) { var aboutContent = response.d; alert(aboutContent); $('#title-en').val(aboutContent.Name); $('#title-vn').val(aboutContent.NameVn); $('#content-en').val(aboutContent.Description); $('#content-vn').val(aboutContent.DescriptionVn); $('#id').val(aboutContent.CategoryId); }, failure: function (message) { alert(message); }, error: function (result) { alert(result); } }); $('#SaveChange').bind('click', function () { updateAbout(); return false; }); $('#Reset').bind('click', function () { getAbout(); return false; }) }); function updateAbout() { var abt = { "CategoryId": $('#id').val(), "Name": $('#title-en').val(), "NameVn": $('#title-vn').val(), "Description": $('#content-en').val(), "DescriptionVn": $('#content-vn').val() }; $.ajax({ type: "POST", url: "AboutManagement.aspx/updateAbout", data: JSON.stringify(abt), contentType: "application/json; charset=utf-8", dataType: "json", success: function (response) { var aboutContent = response.d; $('#title-en').val(aboutContent.Name); $('#title-vn').val(aboutContent.NameVn); $('#content-en').val(aboutContent.Description); $('#content-vn').val(aboutContent.DescriptionVn); }, failure: function (message) { alert(message); }, error: function (result) { alert(result); } }); } </script> Do any approaches to solve it ? Please help me . Thanks

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  • How to sort an NSMutableArray of objects by a member of its class, that is an int or float

    - by J. Dave
    I have a class (from NSObject) that contains: NSString name int position float speed I then create an array (NSMutableArray) of objects from this class. I would like to then sort the array by the 'speed' value, which is a float. I initially has the float value as an NSNumber and the int as NSInteger, and I was successfully sorting with: [myMutableArray sortUsingFunction:compareSelector context:@selector(position)]; where myMutableArray is my array of objects. here is the function: static int compareSelector(id p1, id p2, void *context) { SEL methodSelector = (SEL)context; id value1 = [p1 performSelector:methodSelector]; id value2 = [p2 performSelector:methodSelector]; return [value1 compare:value2]; } Now that I am using int instead of NSInteger, the above code does not work. Is there a more low-level command that I should be using to execute the sort? Thank!

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  • Is it inefficient to access a python class member container in a loop statement?

    - by Dave
    Hi there. I'm trying to adopt some best practices to keep my python code efficient. I've heard that accessing a member variable inside of a loop can incur a dictionary lookup for every iteration of the loop, so I cache these in local variables to use inside the loop. My question is about the loop statement itself... if I have the following class: class A(object): def init(self) self.myList = [ 'a','b','c', 'd', 'e' ] Does the following code in a member function incur one, or one-per-loop-iteration (5) dictionary lookups? for letter in self.myList: print letter IE, should I adopt the following pattern, if I am concerned about efficiency... localList = self.myList for letter in localList: print letter or is that actually LESS efficient due to the local variable assign? Note, I am aware that early optimization is a dangerous pitfall if I'm concerned about the overall efficiency of code development. Here I am specifically asking about the efficiency of the code, not the coding. Thanks in advance! D

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  • How to store NSMutableArray of user defined class objects to file system in iphone?

    - by chaitanya
    Can anyone please tell me how to write NSMutableArray of custom class objects to file? below is the code which i am using to write my array "medicationsArray" to file. medicationsArray contains the objects of below medicationData class @interface medicationData: NSObject { NSString *drName; NSString *date; NSString *description; } @end NSArray *path = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES); NSString *documentDir = [path objectAtIndex:0]; NSString *pathWithFileName; NSString *pathWithFileName = [NSString stringWithFormat:@"%@/medicationsArray",documentDir]; [medicationsArray writeToFile:pathWithFileName atomically:NO]; by using this code i am not able to create a file. can anyone help me in this, thanks in advance

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