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  • Does C++ require a destructor call for each placement new?

    - by Josh Haberman
    I understand that placement new calls are usually matched with explicit calls to the destructor. My question is: if I have no need for a destructor (no code to put there, and no member variables that have destructors) can I safely skip the explicit destructor call? Here is my use case: I want to write C++ bindings for a C API. In the C API many objects are accessible only by pointer. Instead of creating a wrapper object that contains a single pointer (which is wasteful and semantically confusing). I want to use placement new to construct an object at the address of the C object. The C++ object will do nothing in its constructor or destructor, and its methods will do nothing but delegate to the C methods. The C++ object will contain no virtual methods. I have two parts to this question. Is there any reason why this idea will not work in practice on any production compiler? Does this technically violate the C++ language spec?

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  • Using a custom annotation on a Spring MVC controller method from an interceptor.

    - by Speck
    I have a custom annotation with which I've annotated a method in my Controller alongside a @ReqestMapping. The goal is to use the values set in the custom annotation from a HandlerInterceptor to perform a task. I have the interceptor (HandlerInterceptorAdaptor) mapped and it executes. If I set a breakpoint in my concrete Interceptor I can inspect the HttpServletRequest, HttpServletResponse, and handler Objects. However, I cannot see how to 1, obtain the method which the request is trying to access 2, obtain the Annotations on that method and 3, of course, obtain the values set by the annotation. Can anyone point me to good documentation for this? Please and Thank You.

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  • Combining XmlSerializer and XmlWriter?

    - by num3ric
    In addition to a list of objects I am serializing to an xml file using C#'s XmlSerializer, I would like to store a few more independent elements (mainly strings from textboxes) in the same xml. public static void SaveBehaviors(ObservableCollection<Param> listParams) { XmlSerializer _paramsSerializer = new XmlSerializer(listParams.GetType()); string path = Environment.GetFolderPath(Environment.SpecialFolder.Desktop); path += "\\test.xml"; using (TextWriter writeFileStream = new StreamWriter(path)) { _paramsSerializer.Serialize(writeFileStream, listParams); using (XmlWriter writer = XmlWriter.Create(writeFileStream)) { writer.WriteStartElement("Foo"); //test entry... writer.WriteAttributeString("Bar", "Some & value"); writer.WriteElementString("Nested", "data"); writer.WriteEndElement(); } } } However, deserializing "test.xml" results in an error because of the added element. I suppose writing in the serialized xml file is prohibited and should be avoided?

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  • VB.NET: I Cant find the index of an array

    - by steve
    This is the code for my array (which is working) Public numUsers As Integer Public fNameUsers As String = ("..\..\..\users.txt") Public UserRecords As Usersclass() 'note... this line is in a module ' reader = New System.IO.StreamReader(fNameUsers) numUsers = 0 'Split the array up at each delimiter of "," and add new objects ' Do While reader.Peek <> -1 ReDim Preserve UserRecords(numUsers) oneline = reader.ReadLine fields = oneline.Split(",") UserRecords(numUsers) = New Usersclass UserRecords(numUsers).AccountNumber = fields(0) UserRecords(numUsers).CourseName = fields(1) UserRecords(numUsers).FirstName = fields(2) UserRecords(numUsers).LastName = fields(3) UserRecords(numUsers).DOB = fields(4) UserRecords(numUsers).Email = fields(5) UserRecords(numUsers).CourseProgress = (6) UserRecords(numUsers).AdminCheck = fields(7) numUsers = numUsers + 1 Loop reader.Close() My problem is that I don't know how to lookup the index of an array where the .accountNumber = a variable. For example the acccountNumber is 253, what is the code to find the index this relates to???? Thanks in advance

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  • Covariant return types in Java enums

    - by Kelvin Chung
    As mentioned in another question on this site, something like this is not legal: public enum MyEnum { FOO { public Integer doSomething() { return (Integer) super.doSomething(); } }, BAR { public String doSomething() { return (String) super.doSomething(); } }; public Object doSomething(); } This is due to covariant return types apparently not working on enum constants (again breaking the illusion that enum constants are singleton subclasses of the enum type...) So, how about we add a bit of generics: is this legal? public enum MyEnum2 { FOO { public Class<Integer> doSomething() { return Integer.class; } }, BAR { public Class<String> doSomething() { return String.class; } }; public Class<?> doSomething(); } Here, all three return Class objects, yet the individual constants are "more specific" than the enum type as a whole...

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  • Are MongoDB and CouchDB perfect substitutes?

    - by raoulsson
    I haven't got my hands dirty yet with neither CouchDB nor MongoDB but I would like to do so soon... I also have read a bit about both systems and it looks to me like they cover the same cases... Or am I missing a key distinguishing feature? I would like to use a document based storage instead of a traditional RDBMS in my next project. I also need the datastore to handle large binary objects (images and videos) automatically replicate itself to physically separate nodes rendering the need of an additional RDBMS superfluous Are both equally well suited for these requirements? Thanks!

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  • Accessing HttpApplication.Application variables from a class

    - by Young Ninja
    I set up various global parameters in Global.asax, as such: Application["PagePolicies"] = "~/Lab/Policies.aspx"; Application["PageShare"] = "/Share.aspx"; Application["FileSearchQueries"] = Server.MapPath("~/Resources/SearchQueries.xml"); ... I have no problem accessing these variables form .ascx.cs or .aspx.cs file -- ie. files that are part of the Web content. However, I can't seem to access 'Application' from basic class objects (ie. standalone .cs files). I read somewhere to use a slight variations in .cs files, as follows, but it always comes throws an exception when in use: String file = (String)System.Web.HttpContext.Current.Application["FileSearchQueries"];

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  • android exit application completely and go to main applications screen

    - by Totti
    i know that this question is asked many times, but really i can't understand the answer, i want to set button, when user click it i want to exit the application (also the carbage collector should remove the objects), and after exiting i want to go to the screen where the user found the application icon on mobile. for exit i don't know what to do for going to the screen where to find the application icon i tried like this Intent intent = new Intent(Intent.ACTION_MAIN); intent.addCategory(Intent.CATEGORY_HOME); intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK); startActivity(intent); but doesn't work

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  • DataContractAttribute with Shared Assembly

    - by Sanju
    Hi All, Is it necessary to decorate custom objects with [DataContract] and [DataMember] when using shared assemblies (as opposed to auto proxy generation)? The reason I ask is that I have encountered the following scenario: Suppose the following object is implemented in my service: public class baseClass { Guid _guid; public baseClass() { _guid = Guid.NewGuid() } public Guid ReturnGuid { get {return _guid;}} } public class newClass : baseClass { int _someValue; public newClass {} public int SomeValue { get {return _someValue;} set {_someValue = value;} } } [ServiceContract] public IService { [OperationContract] newClass SomeOperation(); } In my client (with shared assemblie) I can happily recieve and use a serialized newClass when SomeOperation is called - even though I have not marked it as a DataContract. However, as soon as I do mark it with DataContract and use DataMember then it complains that set is not implemented on ReturnGuid in the base class. Could somebody explain why it works fine when I do not decorate with DataContract and DataMember. Many thanks.

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  • WPF DrawingVisual from my own class

    - by Robbskinizer
    Hi, Im trying to create my own class which contains a DrawingVisual, something like this public class MyObject { public DrawingVisual visual; public bool faceup; public bool flipped; } I have a drag and drop from a listview to a canvas, but when I try to get the object which back from the Canvas i only get the visual, not any of the other stuff in the class. How do i save "objects" and retreive it from a canvas? Im using my own MyCanvas which inheritance from Canvas, and using the AddVisualChild & AddLogicalChild etc. // Robbin

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  • Objective-c for the iphone: Mystery memory leak

    - by user200341
    My application seems to have 4 memory leaks (on the device, running instruments). The memory leaks seems to come from this code: NSURL *url = [self getUrl:destination]; [destination release]; NSMutableURLRequest *request = [[NSMutableURLRequest alloc] initWithURL:url]; [url release]; [request setHTTPMethod:@"GET"]; [request addValue:@"application/json" forHTTPHeaderField:@"content-type"]; NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:request delegate:self]; [request release]; [connection release]; I am releasing all my objects as far as I can see but it's still showing this as the source of the 4 memory leaks. This is on the Device running 3.1.3 Is it acceptable to have a few memory leaks in your app or do they all have to go?

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  • WPF: Best method for printing paginated datagrids

    - by FauxReal
    Boy did I get an education looking into this. I guess I've been spoiled by Powerbuilder, which has fantastic functionality for this out of the box. Does anyone seriously write custom documentpaginator objects to handle reporting needs for their LOB apps? I want to be able to print "for free" and not have to code like crazy just to take whats on the screen and throw it on paper. How are people doing this? Does anyone have a recommended 3rd party for allowing printing of largish datagrids? Thanks

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  • How can this be done with (N)Hibernate?

    - by Vilx-
    I'm creating a windows forms application with NHibernate. It's an MDI application, so there is no limit to how many forms the user can have open at the same time (probably many). For most forms I want to have an "OK" and a "Cancel" button. Both close the form, but "OK" also saves the modified data to the DB. The forms can be pretty complex, and the modifications are likely to touch a whole graph of objects, adding some, deleting some, and changing some more. It would be good if the changes could be automatically detected and persisted as needed, without the need to manually keep track of each of them. What would be a good way to do this? Extra information: I can make whatever DB schema I want. I'm using MSSQL 2008 and currently have decided for GUID primary keys (with guid.comb generator) and a TIMESTAMP column for optimistic concurrency. I tried to simply set FlushMode of a NHibernate ISession to Never, doing all modifications as needed, and then calling Flush() if the user clicked OK. But that didn't work.

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  • Accessing items from a dictionary using pickle efficiently in Python

    - by user248237
    I have a large dictionary mapping keys (which are strings) to objects. I pickled this large dictionary and at certain times I want to pull out only a handful of entries from it. The dictionary has usually thousands of entries total. When I load the dictionary using pickle, as follows: from cPickle import * # my dictionary from pickle, containing thousands of entries mydict = open(load('mypickle.pickle')) # accessing only handful of entries here for entry in relevant_entries: # find relevant entry value = mydict[entry] I notice that it can take up to 3-4 seconds to load the entire pickle, which I don't need, since I access only a tiny subset of the dictionary entries later on (shown above.) How can I make it so pickle only loads those entries that I have from the dictionary, to make this faster? Thanks.

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  • Delegates vs. events in Cocoa

    - by aaronstacy
    I'm writing my first iPhone app, and I've been exploring the design patterns in Cocoa and Objective-C. I come from a background of client-side web development, so I'm trying to wrap my head around delegates. Specifically, I don't see why delegate objects are needed instead of event handlers. For instance, when the user presses a button, it is handled with an event (UITouchUpInside), but when the user finishes inputting to a text box and closes it with the 'Done' button, the action is handled by calling a method on the text box's delegate (textFieldShouldReturn). Why use a delegate method instead of an event? I also notice this in the view controller with the viewDidLoad method. Why not just use events?

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  • what mysql table structure is better

    - by Sergey
    I have very complicated search algorithm on my site, so i decided to make a table with cache or maybe all possible results. I wanna ask what structure would be better, or maybe not the one of them? (mySQL) 1) word VARCHAR, results TEXT or BLOB where i'll store ids of found objects (for example 6 chars for each id) 2) word VARCHAR, result INT, but words are not unique now i think i'll have about 200 000 rows in 1) with 1000-10000 ids each row or 200 000 000+ rows in 2) First way takes more storage memory but i think it would be much faster to find 1 unique row among 200 000, than 1000 rows among 200 mln non unique rows i think about index on word column and no sphinx. So that do YOU think? p.s. as always, sorry for my english if it's not very good.

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  • Avoid Circular Reference in Swing GUI

    - by drhorrible
    Maybe it's not worth worrying about in this scenario, but lets say you have two classes, a JFrame with all its components, and a server-like class that handles requests from remote clients. The user is able to start and stop server objects through the GUI, and is shown various events that happen to each server object. Whether or not I use an explicit pattern (like MVC), it seems like the JFrame needs a reference to the server class (to call start and stop) and the server needs a reference to the JFrame (to notify of it of certain events). Is this a problem, or am I looking at this situation in the wrong way?

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  • Count number of given object in a list with LINQ

    - by Aaginor
    I have a list which can contain multiple occurrences of the same object. Now I need to count, how often the given object is contained in this list. int count = 0; foreach (IMyObject item in myList) if (item == object2Count) count++; I am sure that this can be done nicer with LINQ, but LINQ is still a mystery to me. My first question is: How would I count the objects via LINQ and the second question: Will this LINQ version be slower or faster? I am using a ObservableCollection and the number of items in the list is usally rather small ... usally not more then 20. Thanks in advance, Frank

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  • Time difference in seconds (as a floating point)

    - by pocoa
    >>> from datetime import datetime >>> t1 = datetime.now() >>> t2 = datetime.now() >>> delta = t2 - t1 >>> delta.seconds 7 >>> delta.microseconds 631000 Is there any way to get that as 7.631000 ? I can use time module, but I also need that t1 and t2 variables as DateTime objects. So if there is a way to do it with datettime, that would be great.

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  • Keeping historic of modification in a database.

    - by mada
    Hi, Im a j2ee developper & we are using hibernatne mapping with a postgres databasae. We have to keep track of any changes occurs in the databse , in others words alls previous & current value of any field should be saved & field can be various types (bytea, int, char...) With a simple table it is easy but we a graph of objets things are more difficult So we have , speaking in a UML point of view, a graph of objects to store in the database with every changes & the user. Any idea or pattern how to do that ? Thanks in advance.

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  • getElementsByTagName() equivalent for textNodes

    - by levik
    Is there any way to get the collection of all textNode objects within a document? getElementsByTagName() works great for Elements, but textNodes are not Elements. Update: I realize this can be accomplished by walking the DOM - as many below suggest. I know how to write a DOM-walker function that looks at every node in the document. I was hoping there was some browser-native way to do it. After all it's a little strange that I can get all the <input>s with a single built-in call, but not all textNodes.

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  • Is there a difference between `==` and `is` in python?

    - by Bernard
    My Google-fu has failed me. In Python, are these: n = 5 # Test one. if n == 5: print 'Yay!' # Test two. if n is 5: print 'Yay!' two tests for equality equivalent (ha!)? Does this hold true for objects where you would be comparing instances (a list say)? Okay, so this kind of answers my question: l = list() l.append(1) if l == [1]: print 'Yay!' # Holds true, but... if l is [1]: print 'Yay!' # Doesn't. So == tests value where is tests to see if they are the same object?

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  • What is the most elegant way to access current_user from the models? or why is it a bad idea?

    - by TheLindyHop
    So, I've implemented some permissions between my users and the objects the users modify.. and I would like to lessen the coupling between the views/controllers with the models (calling said permissions). To do that, I had an idea: Implementing some of the permission functionality in the before_save / before_create / before_destroy callbacks. But since the permissions are tied to users (current_user.can_do_whatever?), I didn't know what to do. This idea may even increase coupling, as current_user is specifically controller-level. The reason why I initially wanted to do this is: All over my controllers, I'm having to check if a user has the ability to save / create / destroy. So, why not just return false upon save / create / destroy like rails' .save already does, and add an error to the model object and return false, just like rails' validations? Idk, is this good or bad? is there a better way to do this?

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  • Silverlight Question: How can I find the DataTemplate corresponding to an item in a ListBox

    - by morpheus
    I have two classes A & B, and a listbox. I assign listBox.ItemsSource equal to a collection of objects of type A. The listbox items are visualized using silverlight data templating, see http://msdn.microsoft.com/en-us/library/system.windows.datatemplate.aspx and http://www.codeproject.com/KB/WPF/UserControlAsDataTemplate.aspx for example. The listbox.ItemTemplate is a DataTemplate that uses class B to visualize the listbox items. Now, in my code-behind, inside any method of class B, if I do this.DataContext, it points to an object of type A. Thus, given an object of type B, I can find the corresponding object of type A. So far so good. My question is, given an object of type A, how can I navigate to the corresponding object of type B? Is this even possible in SL?

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  • How can I bind an Enum to a DbType of bit or int?

    - by uriDium
    Hi I am using Linq2Sql and want to bind an objects field (which is enum) to either a bit or a int type in the database. For example I want have a gender field in my model. I have already edited the DBML and changed the Type to point to my enum. I want to create Radio buttons (which I think I have figured out) for gender and dropdown lists for other areas using the same idea. My enum looks like this public enum Gender { Male, Female } Mapping between DbType 'int' and Type 'Project.Models.Gender' in Column 'Gender' of Type 'Candidate' is not supported. Any ideas on how to do this mapping. Am I missing something on the enums.

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