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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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• Java generics question

  - by user247866

  So I have 3 classes. Abstract class A Class B extends class A independent Class C In class D that contains the main method, I create a list of instances of class B List<B> b = methodCall(); // the method returns a list of instances of class B Now in class C I have one method that is common to both A and B, and hence I don't want to duplicate it. I want to have one method that takes as input an instance of class A, as follows: public void someMethod(List<A> a) However, when I do: C c = new C(); c.someMethod(b); I get an error that some-method is not applicable for the argument List<B>, instead it's expecting to get List<A>. Is there a good way to fix this problem? Many thanks!

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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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• 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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• How to Load IFrame after PageLoad

  - by Empty

  I have one page .aspx, and in page , I have put an iframe on header page. Is it possible that iframe loads after page load finishes?

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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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• JQuery. Check value of select box and textbox with same class, Is it possible?

  - by Cesar Lopez

  I have several select boxes and textboxes with the same class and I have the following statement. if ($('.selTxtClass:visible').val() == "") { $('.selTxtClass:visible').focus(); } } If I do an alert with ($('.selTxtClass:visible').val()) it comes as undefined. I want to check that the value of these elements are empty, but I cant see what is wrong with this if statement, could you give me a hand, please? Thanks a lot.

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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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• What is the default http user agent header sent by the .NET SoapClient class?

  - by Dave Mooney

  What is the default http user agent header sent by the .NET SoapClient class?

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• XML XHR Request resultin in 0 stauts and empty response text.

  - by deepak

  I had another post for the same problem... I think I put the question in a wrong way.. Let me give more details: i have test.html in my c:\ drive and I have a local webserver runnin in qt, and i have some plugin written to that webserver which will get the request and send some response text "hello". in test.html i m making a xml xhr request which will make a GET request like localhost:8080/test which will return the text "hello" by that plugin. Now if I directly open test.html from C:\ it doesnt work, i mean i get response 4 and status 0, and response text nothing.. but the request is passing through webserver and plugin It works fine, when the test.html is put in the webserver pages directory.

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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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• Which exceptions do you catch when you don't specify an exception class in ruby?

  - by Readonly

  Which exceptions are you catching when you don't specify an exception class like this: begin # do something rescue puts "Exception!" end

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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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• 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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• 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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• 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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• 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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• 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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• Is concatenating with an empty string to do a string conversion really that bad?

  - by polygenelubricants

  Let's say I have two char variables, and later on I want to concatenate them into a string. This is how I would do it: char c1, c2; // ... String s = "" + c1 + c2; I've seen people who say that the "" + "trick" is "ugly", etc, and that you should use String.valueOf or Character.toString instead. I prefer this construct because: I prefer using language feature instead of API call if possible In general, isn't the language usually more stable than the API? If language feature only hides API call, then even stronger reason to prefer it! More abstract! Hiding is good! I like that the c1 and c2 are visually on the same level String.valueOf(c1) + c2 suggests something is special about c1 It's shorter. Is there really a good argument why String.valueOf or Character.toString is preferrable to "" +? Trivia: in java.lang.AssertionError, the following line appears 7 times, each with a different type: this("" + detailMessage);

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• How do I create an empty Django formset using modelformset_factory?

  - by nbolton

  I'm creating a formset, but it seems to populate it with all of the existing data in the table for that object. I can't figure out how to start with a blank formset; the only way seems to be to delete all of the data from the table, but clearly this isn't an option. I will post code if necessary (but there's lots of it, so knowing what is relevant is tricky).

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• In Java ,where in memory are class functions put?

  - by husain

  In java ,where in memory are class functions put?

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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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