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• How to initialise a STL vector/list with a class without invoking the copy constructor

  - by Warpspace

  I have a C++ program that uses a std::list containing instances of a class. If I call e.g. myList.push_back(MyClass(variable)); it goes through the process of creating a temporary variable, and then immediately copies it to the vector, and afterwards deletes the temporary variable. This is not nearly as efficient as I want, and sucks when you need a deep copy. I would love to have the constructor of my class new something and not have to implement a copy constructor just to allocate my memory for the second time and waste runtime. I'd also rather not have to immediately find the class instance from the vector/list and then manually allocate the memory (or do something horrible like allocate the memory in the copy constructor itself). Is there any way around this (I'm not using Visual Studio BTW)?

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• objective-c releasing uninitialized class members in dealloc method

  - by Dude Man

  Regarding over-releasing. Say I have a instance variable defined in Test.h NSString *mystring; In my implementation Test.m I do not initialize the variable mystring anywhere. But I release it in dealloc: -(void)dealloc { [mystring release]; } Is this now over-released? I've been doing the following in dealloc to avoid any issues, however, is this really necessary? -(void)dealloc { if (mystring) [mystring release]; } It seems that [nil release] shouldn't do anything, can someone verify this with class members?

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• How to handle this type of model validation in Ruby on Rails

  - by randombits

  I have a controller/model hypothetically named Pets. Pets has the following declarations: :belongs_to owner :has_many dogs :has_many cats Not the best example, but again, it demonstrates what I'm trying to solve. Now when a request comes in as an HTTP POST to http://127.0.0.1/pets, I want to create an instance of Pets. The restriction here is, if the user doesn't submit at least one dog or one cat, it should fail validation. It can have both, but it can't be missing both. How does one handle this in Ruby on Rails? Dogs don't care if cats exists and the inverse is also true. Can anyone show some example code of what the Pets model would look like to ensure that one or the other exists, or fail otherwise? errors.add also takes an attribute, in this case, there is no particular attribute that's failing. It's almost a 'virtual' combination that's missing.

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• Help me understand Dispose() implementation code from MSDN

  - by Benny

  the following code is from MSDN: Idisposable pattern protected virtual void Dispose(bool disposing) { // If you need thread safety, use a lock around these // operations, as well as in your methods that use the resource. if (!_disposed) { if (disposing) { if (_resource != null) _resource.Dispose(); Console.WriteLine("Object disposed."); } // Indicate that the instance has been disposed. _resource = null; _disposed = true; } } why the following statement: _resource = null; _disposed = true; are not enclosed by if (disposing) statement block? for me i would probably write like this: if (disposing) { if (_resource != null) { _resource.Dispose(); _resource = null; _disposed = true; } Console.WriteLine("Object disposed."); } anything wrong with my version?

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• ASP.NET MVC: What is the correct way to redirect to pages/actions in MVC?

  - by Mark Redman

  I am fairly new to MVC but not sure exactly which Redirect... replaces the standard redirect used in WebForms ie the standard Response.Redirect() For instance, I need to redirect to other pages in a couple of scenarios: 1) WHen the user logs out (Forms signout in Action) I want to redirect to a login page 2) In a Controller or base Controller event eg Initialze, I want to redirect to another page (AbsoluteRootUrl + Controller + Action) It seems that multiple redirects get called in some cases which causes errors, something to do with the fact a page is already being redirected? How can cancel the current request and just redirect?

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• Putting a simple if-then statement on one line

  - by Abizern

  I'm just getting into Python and I really like the terseness of the syntax. However; is there an easier way of writing an if-then statement so it fits on one line? For example; say I have the simple test: if count == N: count = 0 else: count = N + 1 is there a simpler way of writing this? I mean, in Objective-C I would write this as: count = count == N ? count = 0 : count = N + 1; Is there something similar for python? Edit I know that in this instance I can use count == count % N. I'm asking about the general syntax.

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• subplot matplotlib wrong syntax

  - by madptr

  I am using matplotlib to subplot in a loop. For instance, i would like to subplot 49 data sets, and from the doc, i implemented it this way; import numpy as np import matplotlib.pyplot as plt X1=list(range(0,10000,1)) X1 = [ x/float(10) for x in X1 ] nb_mix = 2 parameters = [] for i in range(49): param = [] Y = [0] * len(X1) for j in range(nb_mix): mean = 5* (1 + (np.random.rand() * 2 - 1 ) * 0.5 ) var = 10* (1 + np.random.rand() * 2 - 1 ) scale = 5* ( 1 + (np.random.rand() * 2 - 1) * 0.5 ) Y = [ Y[k] + scale * np.exp(-((X1[k] - mean)/float(var))**2) for k in range(len(X1)) ] param = param + [[mean, var, scale]] ax = plt.subplot(7, 7, i + 1) ax.plot(X1, Y) parameters = parameters + [param] ax.show() However, i have an index out of range error from i=0 onwards. Where can i do better to have it works ? Thanks

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• How to implement a ilike Facebook system without user authentication and still prevent users from cheating ?

  - by fabien7474

  Hi, I am trying to implement something done in almost any website out there : a 'ilike' button (like Facebook) that does not require user authetication to be used for any article of my website written in Grails. I don't want to use any external solution, so I need to implement it myself (or use a grails plugin). So my question is : What does it take to implement this 'ilike' button and prevent users from cheating? For instance, do I need to store local cookies (I suppose yes)? Do I need to check the session ID and IP of the HTTP request? Any well-known implementation are welcomed. Thank you very much for your help.

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• Printing UTF-16 strings in JSP is outputted as HTML encoding (&#xxxx)

  - by Ori Osherov

  Hello, When I try to print a UTF-16 string in JSP, specifically Hebrew, it ends up showing up as HTML encoding (&#xxxx). This problem occurs because I print an array of variables into the web page and then parse them. The variables are all UTF-16 strings, but once the servlet prints the variables, it becomes translated to HTML encoding. Is there any way to get rid of the encoding? Thanks in advance Edit for a bit more background: The JSP that I'm printing is not the entirety of the page. It's used in a manner I don't quite understand by a server app which prints the JSPs output into its built in page. As a result, I can't, for instance, use a tag because the will have already been placed somewhere else. This isn't a frame or anything like that. It's just redirected output.

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• Activator.CreateInstance with type name as string and including parameters

  - by Kelly

  I am working in .Net 3.5, looking at all the various constructors for Activator.CreateInstance. I want to create an instance of a class, calling a particular constructor. I do not have the class type, only its name. I have the following, which works, but actually winds up calling the parameterless constructor first, then the one I want. This is not a terribly big deal, but the parameterless constructor calls a rather busy base constructor, and the constructor I want to call does, too. In other words, given a type, calling CreateInstance with parameters is easy (only the last two lines below), but given only a type name, is there a better way than this? ObjectHandle oh = Activator.CreateInstance( "MyDllName", "MyNS." + "MyClassName" ); object o = oh.Unwrap( ); object newObj = Activator.CreateInstance( o.GetType( ), new object[] { param1 } ); return ( IMyDesiredObject )newObject; Thanks!

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• Parse XML with XPath & namespaces in Java

  - by ripper234

  Can you help me adjust this code so it manages to parse the XML? If I drop the XML namespace it works: String webXmlContent = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n" + "<foo xmlns=\"http://foo.bar/boo\"><bar>baz</bar></foo>"; DocumentBuilderFactory domFactory = DocumentBuilderFactory.newInstance(); domFactory.setNamespaceAware(true); DocumentBuilder builder = domFactory.newDocumentBuilder(); org.w3c.dom.Document doc = builder.parse(new StringInputStream(webXmlContent)); NamespaceContextImpl namespaceContext = new NamespaceContextImpl(); namespaceContext.startPrefixMapping("foo", "http://www.w3.org/2001/XMLSchema-instance"); XPath xpath = XPathFactory.newInstance().newXPath(); xpath.setNamespaceContext(namespaceContext); XPathExpression expr = xpath.compile("/foo/bar"); Object result = expr.evaluate(doc, XPathConstants.NODESET); NodeList nodes = (NodeList) result; System.out.println("Got " + nodes.getLength() + " nodes");

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• Need help specifying a ending while condition

  - by johnthexiii

  I have written a Python script to download all of the xkcd comic images. The only problem is I can't tell it to stop when it gets to the last one... Here is what I have so far. import re, mechanize from urllib import urlretrieve from BeautifulSoup import BeautifulSoup as bs baseUrl = "http://xkcd.com/1/" #Specify the first comic page br = mechanize.Browser() #Create a browser response = br.open(baseUrl) #Create an initial response x = 1 #Assign an initial file name while (SomeCondition): soup = bs(response.get_data()) #Create an instance of bs that contains the response data img = soup.findAll('img')[1] #Get the online file path of the image localFile = "C:\\Comics\\xkcd\\" + str(x) + ".jpg" #Come up with a local file name urlretrieve(img["src"], localFile) #Download the image file response = br.follow_link(text = "Next >") #Store the response of the next button x += 1 #Increase x by 1 print "All xkcd comics downloaded" #Let the user know the images have been downloaded Initially what I had was something like while br.follow_link(text = "Next >") != br.follow_link(text = ">|"): but by doing this I actually send skip to the last page before the script has a chance to perform the intended purpose.

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• Is it possible to exit a for before time in C++, if an ending condition is reached?

  - by tunnuz

  Hello, I want to know if it is possible to end a for loop in C++ when an ending condition (different from the reacheing right number of iterations) is verified. For instance: for (int i = 0; i < maxi; ++i) for (int j = 0; j < maxj; ++j) // But if i == 4 < maxi AND j == 3 < maxj, // then jump out of the two nested loops. I know that this is possible in Perl with the next LABEL or last LABEL calls and labeled blocks, is it possible to do it in C++ or I should use a while loop? Thank you.

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• Sleep a thread until an event is attended in another thread from a different class

  - by Afro Genius

  I have an application that fires 2 threads, the 1st launches another class to do some processing which in turn launches a 3rd class to do yet more processing. The 2nd thread in the main class should wait until some event in the 3rd class completes before it performs its job. How can this be achieved? I had tried implementing a wait/notify to share a lock object between the two threads but technically this will not work as I found the hard way. Can I share a lock between classes? Note, an instance of the 3rd class is declared in the 1st class and passed as parameter to the 2nd class. Also I tried creating boolean value in 3rd class that tells when event is complete then poll 2nd thread till this value is true. This worked but is not very desirable. Also is actionListner a better approach to this problem?

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• How to represent a Many-To-Many relationship in XML or other simple file format?

  - by CSharperWithJava

  I have a list management appliaction that stores its data in a many-to-many relationship database. I.E. A note can be in any number of lists, and a list can have any number of notes. I also can export this data to and XML file and import it in another instance of my app for sharing lists between users. However, this is based on a legacy system where the list to note relationship was one-to-many (ideal for XML). Now a note that is in multiple lists is esentially split into two identical rows in the DB and all relation between them is lost. Question: How can I represent this many-to-many relationship in a simple, standard file format? (Preferably XML to maintain backwards compatibility)

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• How does Windows' 'Open with' work?

  - by Frederick

  I was under the impression that when you double click a file (or choose 'Open With' from the right click menu), Windows simply calls the application with the filename as the parameter. Something like this: C: App.exe file.abc However, I just double clicked an .xls file and then checked the PEB of the Excel instance that sprang up. To my surprise the commandline did not contain the filename as a parameter. So that set me wondering. What exactly is mechanism Windows uses to have a file opened by a relevant application? Is there a special API that each application that supports such facility must expose?

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• How to style a standard GWT component (TabBar) differently?

  - by Mike Petterson

  I am using a TabBar and I want to style the component in different ways. So one time this style, another time that style. I thought this will work but it didn't: TabBar t = new TabBar(); t.addTab( "1" ); t.addTab( "2" ); t.addStyleName( MyResources.INSTANCE.css().slickTab() ); And: public interface MyCssResource extends CssResource { String slickTab(); } In the CSS .slickTab .gwt-TabBar .gwt-TabBarItem { background-color: #ff0000; font-weight: normal; } But the appearance don't change. What I am doing wrong?

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• Why wasn't C# designed with 'const' for variables and methods?

  - by spoulson

  I suspect const was simplified for the C# spec for general language simplicity. Was there a specific reason we can't declare variable references or methods as const like we can with C++? e.g.: const MyObject o = new MyObject(); // Want const cast referenece of MyObject o.SomeMethod(); // Theoretically legal because SomeMethod is const o.ChangeStuff(); // Theoretically illegal because ChangeStuff is not const class MyObject { public int val = 0; public void SomeMethod() const { // Do stuff, but can't mutate due to const declaration. } public void ChangeStuff() { // Code mutates this instance. Can't call with const reference. val++; } }

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• Can I override spring beans instatiated with component scanning?

  - by Pablojim

  If I use component scanning in Spring 2.5 but then also define a controller in xml. Do I get two instances of this bean in my application context? If so which instance will be called for its related RequestMappings? <bean id="myController" class="domain.MyController"> <property name="filters"> <list> <ref local="filter1"/> <ref local="filter2"/> </list> </property> </bean>

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• Unable to access static var from Document Class in AS3

  - by omidomid

  I have a Document class called "CityModule", and an asset with class "City". Below is the coe for each. For some reason, I am unable to access the static variables of the City class from CityModule: CityModule.as: package { public class CityModule extends MovieClip { public function CityModule() { var buildings:Array = City.getBuildings(); } } } } City.as: package { import flash.display.MovieClip; public class City extends MovieClip { private static var _buildings:Array = [ {className:'City.Generic1', type:'generic'}, {className:'City.Generic2', type:'generic'}, {className:'City.Generic3', type:'generic'} ]; public function City(){ //empty } public static function getBuildings():Array{ return _buildings; } } } Doing this gives me a "Call to a possibly undefined method getBuildings" error. If I instantiate an instance of City, I can see any public/ getters/ setters perfectly fine. But static isn't working...

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• Can I use a stream to INSERT or UPDATE a row in SQL Server (C#)?

  - by Cheeso

  Suppose I have a VarBinary[MAX] column, can I insert or update into that column using a type derived from System.IO.Stream? How? I think that I can obtain a read-only stream from such a column using a SqlDataReader, calling GetSqlBytes() on the reader, getting the SqlBytes instance, and then referencing the Stream property on that. What I want is the converse - I want a stream for update or insert. Possible? (from c#... Without writing T-SQL ?)

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• Design pattern: polymorphisim for list of objects

  - by ziang

  Suppose I have a class A, and A1, A2 inherits from A. There are 2 functions: List<A1> getListA1(){...} List<A2> getListA2(){...} Now I want to do something similar to both A1 and A2 in another function public void process(List<A>){...} If I want to pass the instance of either ListA1 or ListA2, of course the types doesn't match because the compiler doesn't allow the coercion from List< A1 to List< A. I can't do something like this: List<A1> listA1 = getListA1(); List<A> newList = (List<A>)listA1; //this is not allowed. So what is the best approach to the process()? Is there any way to do it in a universal way rather than write the similar code to both List and List?

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• Single logical SQL Server possible from multiple physical servers?

  - by TuffyIsHere

  Hi, With Microsoft SQL Server 2005, is it possible to combine the processing power of multiple physical servers into a single logical sql server? Is it possible on SQL Server 2008? I'm thinking, if the database files were located on a SAN and somehow one of the sql servers acted as a kind of master, then processing could be spread out over multiple physical servers, for instance even allowing simultaneous updates where there was no overlap, and in the case of read-only queries on unlocked tables no limit. We have an application that is limited by the speed of our sql server, and probably stuck with server 2005 for now. Is the only option to get a single more powerful physical server? Sorry I'm not an expert, I'm not sure if the question is a stupid one. TIA

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• How to extract messages to translate from a Play! application

  - by Martin

  I'm writing my first application using the Play! framework and I was wondering if there was a tool that could extract the messages that need translation from my views and controllers for me ? It is rather cumbersome to fill the conf/messages(.xx) file while I'm developing my app, but I'm afraid that if I don't do it as I go, I will never be able to completely translate my application afterwards. Such tools exist with other framework such as CakePHP for instance, and I think that it shouldn't be hard to write one by myself, but if there already is one... I was also wondering, what should I name the keys of the messages in my application ? Using gettext, it's not bad practice to directly type in the message in english as the key, but is it with the system that Play! uses (MessageFormat, right ?) ? Does anyone have an advice or naming convention (something like controller.action.describe_the_message maybe) ? Thank you for your advices !

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• Overriding setter on domain class in grails 1.1.2

  - by Pavel P

  I have following two domain classes in Grails 1.1.2: class A implements Serializable { MyEnumType myField Date fieldChanged void setMyField(MyEnumType val) { if (myField != null && myField != val) { myField = val fieldChanged = new Date() } } } class B extends A { List children void setMyField(MyEnumType val) { if (myField != null && myField != val) { myField = val fieldChanged = new Date() children.each { child -> child.myField = val } } } When I set B instance's myField, I get the setter into the cycle... myField = val line calls setter again instead of assiging the new value. Any hint how to override the setter correctly? Thanks

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