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  • Understanding C++ pointers (when they point to a pointer)

    - by Stephano
    I think I understand references and pointers pretty well. Here is what I (think I) know: int i = 5; //i is a primitive type, the value is 5, i do not know the address. int *ptr; //a pointer to an int. i have no way if knowing the value yet. ptr = &i; //now i have an address for the value of i (called ptr) *ptr = 10; //go get the value stored at ptr and change it to 10 Please feel free to comment or correct these statements. Now I'm trying to make the jump to arrays of pointers. Here is what I do not know: char **char_ptrs = new char *[50]; Node **node_ptrs = new Node *[50]; My understanding is that I have 2 arrays of pointers, one set of pointers to chars and one to nodes. So if I wanted to set the values, I would do something like this: char_ptrs[0] = new char[20]; node_ptrs[0] = new Node; Now I have a pointer, in the 0 position of my array, in each respective array. Again, feel free to comment here if I'm confused. So, what does the ** operator do? Likewise, what is putting a single * next to the instantiation doing (*[50])? (what is that called exactly, instantiation?)

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  • iPhone: no way to draw on screen outside drawRect?

    - by Seva Alekseyev
    Is there a way to draw on the iPhone screen (on a UIView in a UIWindow) outside of that view's drawRect() method? If so, how do I obtain the graphics context? The graphics guide mentions class NSGraphicsContext, but the relevant chapter seems like a blind copy/paste from Mac OS X docs, and there's no such class in iPhone SDK.

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  • C++ RPC library suggestions

    - by Oxsnarder
    I'm looking for suggestions regarding RPC libraries implemented in C++, for C++ developers. Some requirements constraints: Should work on both linux/unix and win32 systems Be able to execute free function and class methods Hopefully written in modern C++ not 90's/java-esque C++ Be able to function over networks and hetrogenous architectures Not too slow or inefficient Hopefully provide interfaces for TR1 style std::function's et al. My example usage is to invoke the free function foo on a remote machine. ---snip--- // foo translation unit int foo(int i, int j) { return i + j; } ---snip--- ---snip--- // client side main int main() { //register foo on client and server //setup necassary connections and states int result; if (RPCmechanism.invoke("foo",4,9,result)) std::cout << "foo(4,9) = " result << std::endl; else std::cout << "failed to invoke foo(4,9)!" << std::endl; return 0; } ---snip--- Something that can achieve the above or similar would be great.

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  • Access static Method in GDB

    - by Besi
    I recently discovered the GDB in Xcode which makes up for some functionality which IMHO seems to be lacking in Xcode. So I can do the following in GDB: (gdb) po [LoginManager sharedSession].loginToken 20D52FE9-3573-437E-9A65-846572B63726 However, I have another Service class, which is currently not loaded so I get the following error: (gdb) po [SessionService displaySessionInfoForToken:@"XXX"] No symbol "SessionService" in current context. I don't understand why the LoginManager can be loaded but not the SessionService.

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  • Understanding Covariant and Contravariant interfaces in C#

    - by SLC
    I've come across these in a textbook I am reading on C#, but I am having difficulty understanding them, probably due to lack of context. Is there a good concise explanation of what they are and what they are useful for out there? Edit for clarification: Covariant interface: interface IBibble<out T> . . Contravariant interface: interface IBibble<in T> . .

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  • spin_lock_irqsave vs spin_lock_irq

    - by cojocar
    On a SMP machine we must use spin_lock_irqsave and not spin_lock_irq from interrupt context. Why would we want to save the flags (which contains the IF)? Is there another interrupt routine that could interrupt us? The flags are per CPU?

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  • How to use a varying database?

    - by nimo
    I want to use a database which name is stored in a variable. How do I do this? I first thought this would work but it doesn't: exec('use '+@db) That will not change database context Suggestions anyone?

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  • C# ApplicationContext usage

    - by rd42
    Apologies if my terminology is off, I'm new to C#. I'm trying to use an ApplicationContext file to store mysql conn values, like dbname, username, password. The class with mysql conn string is "using" the namespace for the ApplicationContext, but when I print out the connection string, the values are making it. A friend said, "I'm not initializing it" but couldn't stay to expand on what "it" was. and the "Console.WriteLine("1");" in ApplicationContext.cs never shows up. Do I need to create an ApplicationContext object and the call Initialize() on that object? Thanks for any help. ApplicationContext.cs: namespace NewApplication.Context { class ApplicationContext { public static string serverName; public static string username; public static string password; public static void Initialize() { //need to read through config here try { Console.WriteLine("1"); XmlDocument xDoc = new XmlDocument(); xDoc.Load(".\\Settings.xml"); XmlNodeList serverNodeList = xDoc.GetElementsByTagName("DatabaseServer"); XmlNodeList usernameNodeList = xDoc.GetElementsByTagName("UserName"); XmlNodeList passwordNodeList = xDoc.GetElementsByTagName("Password"); } catch (Exception ex) { // MessageBox.Show(ex.ToString()); //TODO: Future write to log file username = "user"; password = "password"; serverName = "localhost"; } } } } MySQLManager.cs: note: dbname is the same as the username as you'll see in the code, I copied this from a friend who does that. using System; using System.Collections.Generic; using System.Linq; using System.Text; using MySql.Data; using MySql.Data.MySqlClient; using NewApplication.Context; namespace NewApplication.DAO { class MySQLManager { private static MySqlConnection conn; public static MySqlConnection getConnection() { if (conn == null || conn.State == System.Data.ConnectionState.Closed) { string connStr = "server=" + ApplicationContext.serverName + ";user=" + ApplicationContext.username + ";database=" + ApplicationContext.username + ";port=3306;password=" + ApplicationContext.password + ";"; conn = new MySqlConnection(connStr); try { Console.WriteLine("Connecting to MySQL... "); Console.WriteLine("Connection string: " + connStr + "\n"); conn.Open(); // Perform databse operations // conn.Close(); } catch (Exception ex) { Console.WriteLine(ex.ToString()); } } return conn; } } } and, thanks for still reading, this is the code that uses the two previous files: class LogDAO { MySqlConnection conn; public LogDAO() { conn = MySQLManager.getConnection(); } Thank you, rd42

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  • How do I connect StaticListableBeanFactory with ClassPathXmlApplicationContext?

    - by Aaron Digulla
    In the setup of my test cases, I have this code: ApplicationContext context = new ClassPathXmlApplicationContext( "spring/common.xml" ); StaticListableBeanFactory testBeanFactory = new StaticListableBeanFactory(); How do I connect the two in such a way that tests can register beans in the testBeanFactory during setup and the rest of the application uses them instead of the ones defined in common.xml? Note: I need to mix a static (common.xml) and a dynamic configuration. I can't use XML for the latter because that would mean to write 1000 XML files.

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  • display the item in tdbmemo from combobox

    - by zizil
    i have combobox that have value category1 and category2...the category1 have items like pencil,food,magazine,newspaper... when i choose category1, i want to retrieve the items in tdbmemo.then the same items in tdbmemo i want to display in checklistbox...i dont know how to do...i use clcat.items.add to display the item but the items is not display procedure TfrmSysConfig.FillInCheckListClCat; var sTable : string; sqlCat : TIBOQuery; iIndex :integer; lstCat : TStringList; begin if tblMain.FieldByName('POS_ReceiptCatBreakDown').AsString <> '' then begin sqlCat := TIBOQuery.Create(nil); sqlCat.IB_Connection := dmMain.db; lstCat := TStringList.Create; try sqlCat.SQL.Text := 'SELECT code FROM ' + cboCategory.Value; sqlCat.Open; while not sqlCat.Eof do begin clCat.Items.Add( sqlCat.FieldByName( 'Code' ).AsString ); sqlCat.Next; end; finally lstCat.Free; sqlCat.Free; end; end; end;

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  • How to use LINQ for CRUD with a simple SQL table?

    - by Rob Ferno
    Every LINQ blog I found there seemed around 2 years old, I understand the syntax but need more direction on creating the SQL mapping and context classes. I just need to use LINQ for 2 SQL tables I have, nothing complicated. Do folks write the SQL mapping classes by hand for such cases or is there a decent tool for this? Can someone point me in the right direction?

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  • sizeof(class) c++

    - by badkya
    How is it possible for sizeof(class) to return two different values depending on context? The class itself should have the same size right irrespective of where I ask this question? I see a smaller value when querying class size from main() and another when I query class size from an extended class.

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  • Tomcat does not persist UserPrinciple during restart

    - by mabuzer
    How to force Tomcat to serialize UserPrinciple so that the user is kept logged in when Tomcat has restarted? Right now the user has to login again everytime. Added the following lines into web-app context.xml: <Manager className="org.apache.catalina.session.PersistentManager"> <Store className="org.apache.catalina.session.FileStore"/> </Manager> but still I see login page after Tomcat restart, I use Tomcat 6.0.26

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  • Eclipse Doesn't List Classes Within Java Packages

    - by Matt Robertson
    Usually when I'm typing a Java import statement in Eclipse or otherwise referencing a class via the packages that it is in, Eclipse shows a context menu with a list of all classes within that package. There have been several times, however, that it would only shows subpackages within a package and would not show classes within that package. Does anyone know why this is? It sounds like a setting/preference was changed, but I never knowingly changed anything related to this.

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  • How to get the name of global active window using Java??

    - by Ansh J
    I am work an Desktop Application in which i need to save the name of corrently focused or active window name(mozilla firefox, or any other file name) in an text file currently I am using getActiveWindow() method of KeyboardFocusManager which give the name of active Window, or null if the active Window is not a member of the calling thread's context. I want to get the name of Global Active window which corrently user is using. Thanks Ansh J Thanks in advance

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  • 301 redirects in .htaccess on apache

    - by WhitechapelTom
    I guess this should be straightforward but my host got me to switch server from zeus to apache following which the .htaccess file with existing individual 301 redirects failed to work causing an internal server error, so have commented them out for the time being. Could someone explain how to set these up to work in their new apache context? Have no apache experience Example redirect: Redirect 301 /pages/exhibitions/thegreatindoors.html http://www.klassnik.com/pages/thegreatindoors.html Read a lot about mod rewrites etc but not sure what to write. Thanks

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  • LINQ to SQL left outer joins

    - by César
    Is this query equivalent to a LEFT OUTER join? var rows = from a in query join s in context.ViewSiteinAdvise on a.Id equals s.SiteInAdviseId where a.Order == s.Order select new {....}; I tried this but it did not result from s in ViewSiteinAdvise join q in query on s.SiteInAdviseId equals q.Id into sa from a in sa.DefaultIfEmpty() where s.Order == a.Order select new {s,a} I need all columns from View

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  • display icon in menuitem (Firefox)

    - by Omar Abid
    I use the following code <menu image="chrome://mecho/content/ic.png" label="Mecho Submission Form" class="menu-iconic" id="mechi-menu" insertafter="context-copylink"> Firefox displays an icon in the menu; however when I use the following (for the submenu) <menuitem label="App" image="chrome://mecho/content/icons/app.png" class="menu-iconic" onclick="mecho.add('katzcd','App')"/> It doesn't show up!! any idea?

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  • How do I handle freeing unmanaged structures on application close?

    - by LostKaleb
    I have a C# project in which i use several unmanaged C++ functions. More so, I also have static IntPtr that I use as parameters for those functions. I know that whenever I use them, I should implement IDisposable in that class and use a destructor to invoke the Dispose method, where I free the used IntPtr, as is said in the MSDN page. public void Dispose() { Dispose(true); GC.SuppressFinalize(this); } private void Dispose(bool disposing) { // Check to see if Dispose has already been called. if (!this.disposed) { if (disposing) { component.Dispose(); } CloseHandle(m_InstanceHandle); m_InstanceHandle = IntPtr.Zero; disposed = true; } } [System.Runtime.InteropServices.DllImport("Kernel32")] private extern static Boolean CloseHandle(IntPtr handle); However, when I terminate the application, I'm still left with a hanging process in TaskManager. I believe that it must be related to the used of the MarshalAs instruction in my structures: [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; } When I create such a structure should I also be careful to free the space it allocs using a destructor? [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Ansi)] public struct SipxAudioCodec { [MarshalAs(UnmanagedType.ByValTStr, SizeConst=32)] public string CodecName; public SipxAudioBandwidth Bandwidth; public int PayloadType; ~SipxAudioCodec() { Marshal.FreeGlobal(something...); } }

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  • computed column calculate a value based on different table

    - by adnan
    i've a table c_const code | nvalue -------------- 1 | 10000 2 | 20000 and i've another table t_anytable rec_id | s_id | n_code --------------------- 2 | x | 1 now i want to calculate the x value with computed column, based on rec_id*(select nvalue from c_const where code=ncode) but i get error "Subqueries are not allowed in this context. Only scalar expressions are allowed." how can i calculate the value in this computed column ? thanks.

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