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  • resource acquisition is initialization "RAII"

    - by hitech
    in the example below class X{ int *r; public: X(){cout<< X is created ; r new int[10]; } ~X(){cout<< X is destroyed ; delete [] r; } }; class Y { public: Y(){ X x; throw 44; } ~Y(){cout<< Y is destroyed ;} }; I got this example of RAII from one site and ave some doubts. please help. in the contructor of x we are not considering the scenation "if the memory allocation fails" . Here for the destructor of Y is safe as in y construcotr is not allocating any memory. what if we need to do some memory allocation also in y constructor?

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  • Avoiding improper std::string initialization with NULL const char* using g++

    - by pachanga
    A there any g++ options which can detect improper initialization of std::string with NULL const char*? I was in the process of turning some int fields into std::string ones, i.e: struct Foo { int id; Foo() : id(0) {} }; ...turned into: struct Foo { std::string id; Foo() : id(0) {} //oooops! }; I completely overlooked bad 'id' initialization with 0 and g++ gave me no warnings at all. This error was detected in the run time(std::string constructor threw an exception) but I'd really like to detect such stuff in the compile time. Is there any way?

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  • SubSonic: MySqlDataReader closes connection.

    - by SchlaWiener
    I am using SubSonic 2.1 and entcountered a problem while executing a Transaction with SharedDbConnectionScope and TransactionScope. The problem is that in the obj.Save() method I get an "The connection must be valid and open" exception I tracked down the problem to this line: // Loads a SubSonic ActiveRecord object User user = new User(User.Columns.Username, "John Doe"); in this Constructor of the User class a method "LoadParam" is called which eventually does if (rdr != null) rdr.Close(); It looks like the rdr.Close() implicitly closes my connection which is fine when using the AutomaticConnection. But during a transaction it is usally not a good idea to close the connection :-) My Question is if this is by design or if it's an error in the MySqlDataReader.

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  • Java File and ByteArray or InputStream - please quick help

    - by Peter Perhác
    I want to use jFuge to play some MIDI music in an applet. There's a class for the MIDI pattern - Pattern - and the only method to load the pattern is from a File. Now, I don't know how applets load files and what not, but I am using a framework (PulpCore) that makes loading assets a simple task. If I need to grab an asset from a ZIP catalogue, I can use the Assets class which provides get() and getAsStream() methods. get() returns the given asset as a ByteArray, the other as an InputStream. I need jFuge to load the pattern from either ByteArray or InputStream. In pseudo-code, I would like to do this: Pattern.load(new File(Assets.get("mymidifile.midi"))); however there is no File constructor that would take a ByteArray. Suggestions, please?

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  • Logging extra fields with Elmah Error Table?

    - by VJ
    I want to add my own session variable to elmah error log table and display it. I already have modified the source code and added the new fields to Error.cs and other fields but I don't know but when I assign an HttpContext.Current.Session["MyVar"].tostring() value to my field in the constructor it stops logging exceptions and does not log any exception. I just need to get the value of the session variable is there other way for this. I read a post which he added fields for the email but it does not say where exactly should I get the session value.

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  • What's the cause of (and treatment for) this java MySQL exception?

    - by justkevin
    I'm getting the following exception when executing the first preparedstatement after a period of inactivity: com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure The last packet successfully received from the server was 2,855,054 milliseconds ago. The last packet sent successfully to the server was 123 milliseconds ago. at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source) at java.lang.reflect.Constructor.newInstance(Unknown Source) at com.mysql.jdbc.Util.handleNewInstance(Util.java:406) at com.mysql.jdbc.SQLError.createCommunicationsException(SQLError.java:1074) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:3052) at com.mysql.jdbc.MysqlIO.reuseAndReadPacket(MysqlIO.java:2938) at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3481) at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1959) at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2109) at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2648) at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2077) at com.mysql.jdbc.PreparedStatement.executeQuery(PreparedStatement.java:2228) This only shows up if my application hasn't communicated with MySQL recently. Subsequent queries execute normally. I suspect it's some kind of timeout issue, but the periods of inactivity are way below the 8 hour timeout for MySQL. Any suggestions?

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  • C# to Java: where T : new() Syntax

    - by Shiftbit
    I am porting some C# code over to Java. I am having trouble with the where Syntax, specifically new(). I understand that where is similar to Java's generic: T extends FOO. How I can replicate the new() argument in Java? "The new() Constraint lets the compiler know that any type argument supplied must have an accessible parameterless--or default-- constructor." - MSDN ie: public class BAR<T> : BAR where T : FOO, new() Right now I have: public class BAR<T extends FOO> extends ABSTRACTBAR { public HXIT(T t){ this.value = t; } .... }

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  • How can I get this code involving unique_ptr to compile?!

    - by Neil G
    #include <vector> #include <memory> using namespace std; class A { public: A(): i(new int) {} A(A const& a) = delete; A(A &&a): i(move(a.i)) {} unique_ptr<int> i; }; class AGroup { public: void AddA(A &&a) { a_.emplace_back(move(a)); } vector<A> a_; }; int main() { AGroup ag; ag.AddA(A()); return 0; } does not compile... (says that unique_ptr's copy constructor is deleted) I tried replacing move with forward. Not sure if I did it right, but it didn't work for me.

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  • What is the rationale to non allow overloading of C++ conversions operator with non-member functio

    - by Vicente Botet Escriba
    C++0x has added explicit conversion operators, but they must always be defined as members of the Source class. The same applies to the assignment operator, it must be defined on the Target class. When the Source and Target classes of the needed conversion are independent of each other, neither the Source can define a conversion operator, neither the Target can define a constructor from a Source. Usually we get it by defining a specific function such as Target ConvertToTarget(Source& v); If C++0x allowed to overload conversion operator by non member functions we could for example define the conversion implicitly or explicitly between unrelated types. template < typename To, typename From operator To(const From& val); For example we could specialize the conversion from chrono::time_point to posix_time::ptime as follows template < class Clock, class Duration operator boost::posix_time::ptime( const boost::chrono::time_point& from) { using namespace boost; typedef chrono::time_point time_point_t; typedef chrono::nanoseconds duration_t; typedef duration_t::rep rep_t; rep_t d = chrono::duration_cast( from.time_since_epoch()).count(); rep_t sec = d/1000000000; rep_t nsec = d%1000000000; return posix_time::from_time_t(0)+ posix_time::seconds(static_cast(sec))+ posix_time::nanoseconds(nsec); } And use the conversion as any other conversion. So the question is: What is the rationale to non allow overloading of C++ conversions operator with non-member functions?

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  • How to implement exception chaining in PHP

    - by Josef Sábl
    Constructor for PHP's exception has third parameter, documentation says: $previous: The previous exception used for the exception chaining. But I can't make it work. My code looks like this: try { throw new Exception('Exception 1', 1001); } catch (Exception $ex) { throw new Exception('Exception 2', 1002, $ex); } I expect Exception 2 to be thrown and I expect that it will have Exception 1 attached. But all I get is: Fatal error: Wrong parameters for Exception([string $exception [, long $code ]]) in ... What am I doing wrong?

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  • Smart pointers and polymorphism

    - by qwerty
    hello. I implemented reference counting pointers (called SP in the example) and im having problems with polymorphism which i think i shouldn't have. In the following code: SP<BaseClass> foo() { // Some logic... SP<DerivedClass> retPtr = new DerivedClass(); return retPtr; } DerivedClass inherits from BaseClass. With normal pointers this should have worked, but with the smart pointers it says "cannot convert from 'SP<T>' to 'const SP<T>&" and i think it refers to the copy constructor of the smart pointer. How to i allow this kind of polymorphism with reference counting pointer? I'd appreciate code samples cause obviously im doing something wrong here if im having this problem. Thanks! :) [p.s., plz don't tell me to use standart liberary with smart pointers cuz that's impossible at this moment.]

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  • MEF part unable to import Autofac autogenerated factory

    - by Michael Wagner
    This is a (to me) pretty weird problem, because it was already running perfectly but went completely south after some unrelated changes. I've got a Repository which imports in its constructor a list of IExtensions via Autofacs MEF integration. One of these extensions contains a backreference to the Repository as Lazy(Of IRepository) (lazy because of the circular reference that would occur). But as soon as I try to use the repository, Autofac throws a ComponentNotRegisteredException with the message "The requested service 'ContractName=Assembly.IRepository()' has not been registered." That is, however, not really correct, because when I break right after the container-build and explore the list of services, it's there - Exported() and with the correct ContractName. I'd appreciate any help on this... Michael

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  • Correct way to trigger object clone/memento when property changes

    - by Jay
    Hi, I have a big doubt about the correct way to save an object state (clone object), if necessary to rollback the changes, when a property has changed. I know that the IEditableObject interface exists for those cases but during some tests the BeginEdit would just fire like crazy (I have a DataGrid whose values can be edited but I won't need to keep the state of the object in these cases). I'm following the MVP design pattern in my project and the view's DataContext is a wrapper of my presenter.Let's say I have a CheckBox/TextBox in my UI and when that textbox's value changes, the property bound in the wrapper gets set.Currently, before setting the new value i'm raising an event to the presenter (something like PropertyChanging) that clones my wrapper. I'm doing this because I don't think that job should be done by the wrapper itself but by the presenter.Is this a correct approach? Raising the event is an acceptable solution? I thought of other possible ideas: Interface between presenter and wrapper; Use explicit binding and trigger the binding after saving object's state; What is your opinion about the best way to do this? Should I just keep IEditableObject, is this the best way? Best Regards

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  • Approaches to use Repositories (w/ StructureMap) with AutoMapper?

    - by jacko
    Any idea how I can tell AutoMapper to resolve a TypeConverter constructor argument using StructureMap? ie. We have this: private class GuidToContentProviderConverter : TypeConverter<Guid, ContentProvider> { private readonly IContentProviderRepository _repository; public GuidToContentProviderConverter(IContentProviderRepository repository) { _repository = repository; } protected override ContentProvider ConvertCore(Guid contentProviderId) { return _repository.Get(contentProviderId); } } And in the AutoMap registration: Mapper.CreateMap<Guid, ContentProvider>().ConstructUsing<GuidToContentProviderConverter>(); However, this generates a compile-time error about ctor args. Any ideas? Or ideas to other approaches for using Automapper to hydrate domain objects from viewmodel ID's using a repository?

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  • How do I determine if a JDialog has children?

    - by Morinar
    I've got a custom window class that is a couple levels down extending a JDialog. We have windows that we create and sometimes we create new windows as children of existing windows using the constructor that takes a parent argument. I need to put some code somewhere in our custom class that does something different depending on whether not the window has children. I know of getParent(), etc, and I can see that I can loop through the components of the window, but for the life of me, I can't seem to figure out how to determine whether or not my current window has any child windows. Is there a way to do this? Any help is, as always, much appreciated.

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  • .NET and Closing SQL Server connections

    - by user307076
    I am having a hard time figuring out why the following constructor will not close connnections. When I view the active connections. Here is the code that I have. Public Sub New(ByVal UserID As Integer) Dim oConn As New SqlConnection(ConfigurationManager.ConnectionStrings("connStr").ToString()) Dim cmd As New SqlCommand("stored proc", oConn) Dim sdr As SqlDataReader cmd.CommandType = CommandType.StoredProcedure cmd.Parameters.AddWithValue("@userID", UserID) oConn.Open() sdr = cmd.ExecuteReader() Try If Not sdr.HasRows Then sdr.Close() If Not oConn Is Nothing Then If oConn.State <> ConnectionState.Closed Then oConn.Close() End If End If cmd.Dispose() Exit Sub End If 'User has account in WATS, proceed to load account information While sdr.Read _firstname = Convert.ToString(sdr("First Name")) _lastname = Convert.ToString(sdr("Last Name")) End While Catch ex As Exception 'Throw New Exception("User Error: " + ex.Message) Finally sdr.Close() If Not oConn Is Nothing Then If oConn.State <> ConnectionState.Closed Then oConn.Close() End If End If cmd.Dispose() End Try End Sub

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  • Static Class Variables in Dynamic Library and Main Program

    - by Paul
    I am working on a project that has a class 'A' that contains a static stl container class. This class is included in both my main program and a .so file. The class uses the default(implicit, not declared) constructor/destructor. The main program loads the .so file using dlopen() and in its destructor, calls dlclose(). The program crashes after main exits when glibc calls the destructor for the static class member variable. The problem appears to be that when dlclose() is called, the destructor for the static variable is called, then when main exits() glibc also calls the destructor, resulting in a double free. I have 2 questions, namely: 1) In this particular case, why are there not two copies of the static variable(yes i know that sounds somewhat ridiculous, but since both the main program and .so file have a separately compiled 'A', shouldn't they each have one?) 2) Is there any way to resolve this issue without re-writing class 'A' to not contain static member variables?

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  • How do I process a nested list?

    - by ddbeck
    Suppose I have a bulleted list like this: * list item 1 * list item 2 (a parent) ** list item 3 (a child of list item 2) ** list item 4 (a child of list item 2 as well) *** list item 5 (a child of list item 4 and a grand-child of list item 2) * list item 6 I'd like to parse that into a nested list or some other data structure which makes the parent-child relationship between elements explicit (rather than depending on their contents and relative position). For example, here's a list of tuples containing an item and a list of its children (and so forth): [('list item 1',), ('list item 2', [('list item 3',), [('list item 4', [('list item 5'),]] ('list item 6',)] I've attempted to do this with plain Python and some experimentation with Pyparsing, but I'm not making progress. I'm left with two major questions: What's the strategy I need to employ to make this work? I know recursion is part of the solution, but I'm having a hard time making the connection between this and, say, a Fibonacci sequence. I'm certain I'm not the first person to have done this, but I don't know the terminology of the problem to make fruitful searches for more information on this topic. What problems are related to this so that I can learn more about solving these kinds of problems in general?

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  • android custom map marker bounds

    - by max4ever
    Hello i am using a resized version of this marker( http://www.clker.com/clipart-orange-pin-4.html ) for showing markers in google maps on android. The problem is i don't know how to make the marker point match the coordinates. The arrow point is at about 1/5 of the Width coordinates and MAX of the Height. here is my class public class GestionaleItemizedOverlay extends com.google.android.maps.ItemizedOverlay { public GestionaleItemizedOverlay(Drawable defaultMarker, Context context) { //super(boundCenterBottom(defaultMarker)); super(boundCenter(defaultMarker)); this.mContext = context; } ... And this this.marker_poi = this.getContext().getResources().getDrawable(R.drawable.marker); this.marker_poi.setBounds(this.marker_poi.getIntrinsicWidth() / 2, this.marker_poi.getIntrinsicHeight(), this.marker_poi.getIntrinsicWidth() / 2, 0); new GestionaleItemizedOverlay(this.poi, this.context); Do i need to setBounds on the marker before passing it to the constructor? and why does super(defaultMarker) makes all the markers not to show ?

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  • Why does my NSWindow only receive mouseOver events the first time?

    - by DanieL
    I have an application where a borderless window is shown and hidden, using orderOut and orderFront. When it is visible, I want the it to become the key window when the mouse moves over it. So far I've done this: In awakeFromNib I have set its first responder to itself. In the window's constructor I set accepts mouse events to YES. In the mouseMoved method, I use makeKeyAndOrderToFront. My problem is, that this only works the first time I move the mouse over the window. After that, it doesn't receive any mouseOver events. I've tried checking the firstResponder but as far as I can tell it never changes from the window. Any ideas what I can do to get this working?

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  • Getting "value is not defined" while inheriting a type

    - by James Black
    I can't see what I am doing wrong, as the files are in the correct order. In this case it is: BaseDAO.fs CreateDatabase.fs They are in the same namespace, but even when I had them in different modules, and opened the module in CreateDatabase the same error. The error is: Error 1 The value or constructor 'execNonQuery' is not defined I am trying to inherit BaseDAO and use a member that will be common to several files, and I don't see why I get the error above. namespace RestaurantServiceDAO open MySql.Data.MySqlClient type BaseDAO() = let connString = @"Server=localhost;Database=mysql;Uid=root;Pwd=$$$$;" let conn = new MySqlConnection(connString) member self.execNonQuery(sqlStr) = conn.Open() let comm = new MySqlCommand(sqlStr, conn, CommandTimeout = 10) comm.ExecuteNonQuery |> ignore comm.Dispose |> ignore The type that does inherit is here, and execNonQuery is not defined. namespace RestaurantServiceDAO open MySql.Data.MySqlClient type CreateDatabase() = inherit BaseDAO() let createRestaurantTable conn = execNonQuery "CREATE TABLE restaurant(id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, name VARCHAR(100), cur_timestamp TIMESTAMP(8))"

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  • .NET and Closing MSSQL connections

    - by user307076
    I am having a hard time figuring out why the following constructor will not close connnections. When I view the active connections. Here is the code that I have. Public Sub New(ByVal UserID As Integer) Dim oConn As New SqlConnection(ConfigurationManager.ConnectionStrings("connStr").ToString()) Dim cmd As New SqlCommand("stored proc", oConn) Dim sdr As SqlDataReader cmd.CommandType = CommandType.StoredProcedure cmd.Parameters.AddWithValue("@userID", UserID) oConn.Open() sdr = cmd.ExecuteReader() Try If Not sdr.HasRows Then sdr.Close() If Not oConn Is Nothing Then If oConn.State <> ConnectionState.Closed Then oConn.Close() End If End If cmd.Dispose() Exit Sub End If 'User has account in WATS, proceed to load account information While sdr.Read _firstname = Convert.ToString(sdr("First Name")) _lastname = Convert.ToString(sdr("Last Name")) End While Catch ex As Exception 'Throw New Exception("User Error: " + ex.Message) Finally sdr.Close() If Not oConn Is Nothing Then If oConn.State <> ConnectionState.Closed Then oConn.Close() End If End If cmd.Dispose() End Try End Sub

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  • enums in C# - assignment

    - by Zka
    How does one do this in c#? Let's say that myclass has : private enum Days{}; 1) How does one add data to the enum inside the myclass with the help of the constructor? As in : myclass my = new myclass(Monday,Friday); so that the enum inside the class gets the "Monday, Friday" properties. 2) Can one also make a property for an enume inside the class once it is initialized ? For example : my.Days = new enum Days(Tuesday); //where the old settings are replaced.

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  • Initialize Pointer Through Function

    - by SoulBeaver
    I was browsing my teacher's code when I stumbled across this: Order* order1 = NULL; then order1 = order(customer1, product2); which calls Order* order(Customer* customer, Product* product) { return new Order(customer, product); } This looks like silly code. I'm not sure why, but the teacher initialized all pointers to NULL instead of declaring them right away(looking at the code it's entirely possible, but he chose not to). My question is: is this good or acceptable code? Does the function call have any benefits over calling a constructor explicitely? And how does new work in this case? Can I imagine the code now as kind of like: order1 = new Order(customer, product);

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  • Django : proper way to use model, duplicates!

    - by llazzaro
    Hello, I have a question about the proper, best way to manage the model. I am relative newbie to django, so I think I need to read more docs, tutorials,etc (suggestions for this would be cool!). Anyway, this is my question : I have a python web crawler, that is "connected" with django model. Crawling is done once a day, so its really common to find "duplicates". To avoid duplicates I do this : cars = Car.Objects.filter(name=crawledItem['name']) if len(cars) 0: #object already exists, update it car = cars[0] else: car = Car() #some non-relevant code here car.save() I want to know, if this is the proper/correct way to do it or its any "automatic" way to do it. Its possible to put the logic inside the Car() constructor also, should I do that? Thanks a lot!

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