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  • Returning pointers in a thread-safe way.

    - by Roddy
    Assume I have a thread-safe collection of Things (call it a ThingList), and I want to add the following function. Thing * ThingList::findByName(string name) { return &item[name]; // or something similar.. } But by doing this, I've delegated the responsibility for thread safety to the calling code, which would have to do something like this: try { list.lock(); // NEEDED FOR THREAD SAFETY Thing *foo = list.findByName("wibble"); foo->Bar = 123; list.unlock(); } catch (...) { list.unlock(); throw; } Obviously a RAII lock/unlock object would simplify/remove the try/catch/unlocks, but it's still easy for the caller to forget. There are a few alternatives I've looked at: Return Thing by value, instead of a pointer - fine unless you need to modify the Thing Add function ThingList::setItemBar(string name, int value) - fine, but these tend to proliferate Return a pointerlike object which locks the list on creation and unlocks it again on destruction. Not sure if this is good/bad practice... What's the right approach to dealing with this?

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  • Function returning MYSQL_ROW

    - by Gabe
    I'm working on a system using lots of MySQL queries and I'm running into some memory problems I'm pretty sure have to do with me not handling pointers right... Basically, I've got something like this: MYSQL_ROW function1() { string query="SELECT * FROM table limit 1;"; MYSQL_ROW return_row; mysql_init(&connection); // "connection" is a global variable if (mysql_real_connect(&connection,HOST,USER,PASS,DB,0,NULL,0)){ if (mysql_query(&connection,query.c_str())) cout << "Error: " << mysql_error(&connection); else{ resp = mysql_store_result(&connection); //"resp" is also global if (resp) return_row = mysql_fetch_row(resp); mysql_free_result(resp); } mysql_close(&connection); }else{ cout << "connection failed\n"; if (mysql_errno(&connection)) cout << "Error: " << mysql_errno(&connection) << " " << mysql_error(&connection); } return return_row; } And function2(): MYSQL_ROW function2(MYSQL_ROW row) { string query = "select * from table2 where code = '" + string(row[2]) + "'"; MYSQL_ROW retorno; mysql_init(&connection); if (mysql_real_connect(&connection,HOST,USER,PASS,DB,0,NULL,0)){ if (mysql_query(&connection,query.c_str())) cout << "Error: " << mysql_error(&conexao); else{ // My "debugging" shows me at this point `row[2]` is already fubar resp = mysql_store_result(&connection); if (resp) return_row = mysql_fetch_row(resp); mysql_free_result(resp); } mysql_close(&connection); }else{ cout << "connection failed\n"; if (mysql_errno(&connection)) cout << "Error : " << mysql_errno(&connection) << " " << mysql_error(&connection); } return return_row; } And main() is an infinite loop basically like this: int main( int argc, char* args[] ){ MYSQL_ROW row = NULL; while (1) { row = function1(); if(row != NULL) function2(row); } } (variable and function names have been generalized to protect the innocent) But after the 3rd or 4th call to function2, that only uses row for reading, row starts losing its value coming to a segfault error... Anyone's got any ideas why? I'm not sure the amount of global variables in this code is any good, but I didn't design it and only got until tomorrow to fix and finish it, so workarounds are welcome! Thanks!

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  • Serializable object in intent returning as String

    - by B_
    In my application, I am trying to pass a serializable object through an intent to another activity. The intent is not entirely created by me, it is created and passed through a search suggestion. In the content provider for the search suggestion, the object is created and placed in the SUGGEST_COLUMN_INTENT_EXTRA_DATA column of the MatrixCursor. However, when in the receiving activity I call getIntent().getSerializableExtra(SearchManager.EXTRA_DATA_KEY), the returned object is of type String and I cannot cast it into the original object class. I tried making a parcelable wrapper for my object that calls out.writeSerializable(...) and use that instead but the same thing happened. The string that is returned is like a generic Object toString(), i.e. com.foo.yak.MyAwesomeClass@4350058, so I'm assuming that toString() is being called somewhere where I have no control. Hopefully I'm just missing something simple. Thanks for the help! Edit: Some of my code This is in the content provider that acts as the search authority: //These are the search suggestion columns private static final String[] COLUMNS = { "_id", // mandatory column SearchManager.SUGGEST_COLUMN_TEXT_1, SearchManager.SUGGEST_COLUMN_INTENT_EXTRA_DATA }; //This places the serializable or parcelable object (and other info) into the search suggestion private Cursor getSuggestions(String query, String[] projection) { List<Widget> widgets = WidgetLoader.getMatches(query); MatrixCursor cursor = new MatrixCursor(COLUMNS); for (Widget w : widgets) { cursor.addRow(new Object[] { w.id w.name w.data //This is the MyAwesomeClass object I'm trying to pass }); } return cursor; } This is in the activity that receives the search suggestion: public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Object extra = getIntent().getSerializableExtra(SearchManager.EXTRA_DATA_KEY); //extra.getClass() returns String, when it should return MyAwesomeClass, so this next line throws a ClassCastException and causes a crash MyAwesomeClass mac = (MyAwesomeClass)extra; ... }

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  • returning opengl display callback in D

    - by Max
    I've written a simple hello world opengl program in D, using the converted gl headers here. My code so far: import std.string; import c.gl.glut; Display_callback display() { return Display_callback // line 7 { return; // just display a blank window }; } // line 10 void main(string[] args) { glutInit(args.length, args); glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE); glutInitWindowSize(800,600); glutCreateWindow("Hello World"); glutDisplayFunc(display); glutMainLoop(); } My problem is with the display() function. glutDisplayFunc() expects a function that returns a Display_callback, which is typedef'd as typedef GLvoid function() Display_callback;. When I try to compile, dmd says line 7: found '{' when expecting ';' following return statement line 10: unrecognized declaration How do I properly return the Display_callback here? Also, how do I change D strings and string literals into char*? My calls to glutInit and glutCreateWindow don't like the D strings they're getting. Thanks for your help.

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  • [java] Returning the element number of the longest string in an array

    - by JohnRoberts
    Hoookay, so. I'm trying to get the longestS method to take the user-inputted array of strings, then return the element number of the longest string in that array. I got it to the point where I was able to return the number of chars in the longest string, but I don't believe that will work for what I need. My problem is that I keep getting incompatible type errors when trying to figure this out. I don't understand the whole data type thing with strings yet. It's confusing me how I go about return a number of the array yet the array is of strings. The main method is fine, I got stuck on the ???? part. { public static void main(String [] args) { Scanner inp = new Scanner( System.in ); String [] responseArr= new String[4]; for (int i=0; i<4; i++) { System.out.println("Enter string "+(i+1)); responseArr[i] = inp.nextLine(); } int highest=longestS(responseArr); } public static int longestS(String[] values) { int largest=0 for( int i = 1; i < values.length; i++ ) { if ( ????? ) } return largest; } }

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  • Linq and returning types

    - by cdotlister
    My GUI is calling a service project that does some linq work, and returns data to my GUI. However, I am battling with the return type of the method. After some reading, I have this as my method: public static IEnumerable GetDetailedAccounts() { IEnumerable accounts = (from a in Db.accounts join i in Db.financial_institution on a.financial_institution.financial_institution_id equals i.financial_institution_id join acct in Db.z_account_type on a.z_account_type.account_type_id equals acct.account_type_id orderby i.name select new {account_id = a.account_id, name = i.name, description = acct.description}); return accounts; } However, my caller is battling a bit. I think I am screwing up the return type, or not handling the caller well, but it's not working as I'd hoped. This is how I am attempting to call the method from my GUI. IEnumerable accounts = Data.AccountService.GetDetailedAccounts(); Console.ForegroundColor = ConsoleColor.Green; Console.WriteLine("Accounts:"); Console.ForegroundColor = ConsoleColor.White; foreach (var acc in accounts) { Console.WriteLine(string.Format("{0:00} {1}", acc.account_id, acc.name + " " + acc.description)); } int accountid = WaitForKey(); However, my foreach, and the acc - isn't working. acc doesn't know about the name, description and id that I setup in the method. Am I at least close to being right?

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  • jQuery Ajax Methods Not Returning XHR Object

    - by Nate
    UPDATE: I haven't figured out what's going on, but this definitely seems to be a problem with my project. After creating a simple test page, I was able to verify that getJSON does in fact return an XHR object like it's supposed to. Per the stackoverflow question/answer here: Kill ajax requests using javascript using jquery. and a number of other question/answers on this site and others, the jQuery Ajax methods should return the XHR object. However, when I run the following code, request is "undefined". var request = $.getJSON(url, function(data) { console.log(data); }); console.log(request); Did I miss a change in jQuery? I'm using 1.4.4.

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  • Code crashing compiler: main() returning a struct instead of an int

    - by AndrejaKo
    Hi! I'm experimenting with a piece of C code. Can anyone tell me why is VC 9.0 with SP1 crashing for me? Oh, and the code is meant to be an example used in a discussion why something like void main (void) is evil. struct foo { int i; double d; } main (double argc, struct foo argv) { struct foo a; a.d=0; a.i=0; return a.i; } If I put return a; compiler doesn't crash.

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  • Returning a local object from a function

    - by pocoa
    Is this the right way to return an object from a function? Car getCar(string model, int year) { Car c(model, year); return c; } void displayCar(Car &car) { cout << car.getModel() << ", " << car.getYear() << endl; } displayCar(getCar("Honda", 1999)); I'm getting an error, "taking address of temporary". Should I use this way: Car &getCar(string model, int year) { Car c(model, year); return c; }

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  • Linq to SQL - Returning two values with one query

    - by Sir Psycho
    Hi, Is it possible to return a single value and an enumerable collection using LINQ to SQL? The problem is, I'm trying to do paging across a large recordset. I only want to return 10 rows at a time so I'm using .Skip(20).Take(10) approach. However I need to know the total number of records so I can show an appropriate page x of y. Trying to avoid two separate queries. Thanks

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  • Returning messages in Smalltalk

    - by Zachary
    I have a Dictionary of objects I have created in smalltalk, which I am iterating over by enumerating it based on the key/value pairs. For value object in the dictionary, I am calling a method on that object. Based on certain conditions, I would like for this object to be able to add a new member to dictionary, and possibly delete another one. I've been looking at the 'Perform' and 'Messages' facilities in Smalltalk, but I'm not sure if it is even possible to do what I'm trying to do - is it possible to return a message (or multiple messages), which another object can process and perform? For example, could my method return 'removeKey: 19' and 'add object' at the same time? I am using GNU Smalltalk, if it matters.

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  • Bitmap .compress() returning false

    - by Tsimmi
    Hi! The next call to Bitmap.compress(), has a different behavior on the Emulator and on a real device. In the Emulator, result is true, and in a real device the same call returns false. FileOutputStream fos = new FileOutputStream(destinationFile, true); boolean result = myBitmap.compress(Bitmap.CompressFormat.PNG, 100, fos); The thing is that on the emulator this is working great, on a real device ( a HERO) when calling .compress(), this returns false, witch means that it was unable to convert the image properly. Why is this? Thank you

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  • PHP: Prevent chained method from returning?

    - by Industrial
    Hi, I am having some headaches regarding method chaining for a quite simple PHP class that returns a value, which sometimes need to go through a decryption process: $dataset = new Datacontainer; $key = $dataset->get('key'); $key2 = $dataset->get('key')->decrypt(); The get method is where the return lives. So the call to the decrypt method on the second row isn't going to work in its current state. Can I do something to setup the get method to return only when nothing is chained to it, or what would be the best way to re-factor this code?

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  • Returning the index number of an Arraylist in Java

    - by Daniel
    I would like my method public void showClassRoomDetails(String teacherName) to return the Arraylist index number using the teacherName. Thanks import java.util.ArrayList; public class School { private ArrayList<Classroom> classrooms; private String classRoomName; private String teacherName; public School() { classrooms = new ArrayList<Classroom>(); } public void addClassRoom(Classroom newClassRoom, String theClassRoomName) { classrooms.add(newClassRoom); classRoomName = theClassRoomName; } public void addTeacherToClassRoom(int classroomId, String TeacherName) { if (classroomId < classrooms.size() ) { classrooms.get(classroomId).setTeacherName(TeacherName); } } public void showClassRoomDetails(String teacherName) { for (Classroom classroom : this.classrooms) { if (classroom.returnTeacherName().equals(teacherName)) { System.out.println(classroom.returnClassRoomName()); System.out.println(classroom.returnTeacherName()); break; } } } }

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  • SSRS Dynamic Returning Dataset Collection Field in Expression

    - by Ray Clark
    I wrote a custom assembly to take a parameter value from the report and return a field from the dataset collection. My assembly returns the correct fields!name.value, but it shows me the string representation of it. How can I get it to resolve as the actual fields!name.value to display the actual data in the dataset? If I enter fields!name.value in manually it works fine showing me the value. If I resolve it with my custom code it display "fields!name.value" to me in the cell.

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  • Idatareaders not returning values from database

    - by Phil
    In my codebehind I have this vb: Dim reader as idatareader = includes.SelectDepartmentID(PageID) While reader.Read Did = reader("departmentid") GroupingHeading = reader("heading") Folder = reader("folder") If reader("OwnBanner") Is DBNull.Value Then OwnBanner = String.Empty Else OwnBanner = reader("ownbanner") End If Then in my class I have: Public Function SelectDepartmentID(ByVal PageID As Integer) As IDataReader Dim Command As SqlCommand = db.GetSqlStringCommand("sql") db.AddInParameter(Command, "@pageid", Data.DbType.Int32, PageID) Dim reader As IDataReader = db.ExecuteReader(Command) reader.Read() Return reader End Function No Errors are being presented yet nothing is being returned by the reader. Is there an error in my code? Thanks.

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  • Object-C: initWithContentsOfURL returning null

    - by AragornSG
    Hey! I'm working on an app that would display a remote html and use local images, so what I'm trying to do is download the HTML of the website and display it as a "local" page, that would have access to images in my bundle. For some reason I can't get initWithContentsOfURL to work. I checked all manuals and examples I could find and it seems that I'm doing it correctly, but the thing just won't work, returns null all the time. The same page loaded with NSURLRequest requestWithURL works fine. Appreciate your help! Here is the code: - (void)awakeFromNib { appURL = @"http://dragontest.fantasy-fan.org"; notConnectedHTML = @"Could not connect."; NSString *seedString = [[NSString alloc] initWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:@"%@/seed.php", appURL]]]; NSString *HTMLdata = @""; if (seedString = @"(null)") { NSLog(@"Can't connect on awakeFromNib."); HTMLdata = notConnectedHTML; }else { HTMLdata = [NSString stringWithFormat:@"<body style='padding:0px;margin:0px;'>%@%@</body>", seedString, @"<br><img src='images/Default.png'>"]; } [homeView loadHTMLString:HTMLdata baseURL:[NSURL fileURLWithPath:[[NSBundle mainBundle] resourcePath]]]; }

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  • C++ containers on classes, returning pointers

    - by otneil
    Hello, I'm having some trouble to find the best way to accomplish what I have in mind due to my inexperience. I have a class where I need to a vector of objects. So my first question will be: is there any problem having this: vector< AnyType container* and then on the constructor initialize it with new (and deleting it on the destructor)? Another question is: if this vector is going to store objects, shouldn't it be more like vector< AnyTipe* so they could be dynamically created? In that case how would I return an object from a method and how to avoid memory leaks (trying to use only STL)?

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  • FluentNHibernate: returning an enum from a derived property

    - by Zen-C
    I'm using the automapping feature of FluentNHibernate and need a property that derives its return value. This property must return an Enum value, e.g. public virtual MyEnum MyDerivedProperty { get { MyEnum retval; // do some calculations return retval; } } Currently I get the following exception: NHibernate.PropertyNotFoundException: Could not find a setter for property 'MyDerivedProperty' ... If I add a setter then the database table involved requires the column to exist, even if that setter does nothing. It works fine when the return type is an int. Any ideas how I achieve this?

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  • Run Oracle Procedure just to lock row, without returning a resultset

    - by Pascal
    I want to run a procedure to force a row lock on a row, but I don't want to return a result set to the client, nor do I actually want to update anything. Below is the proc: CREATE OR REPLACE PROCEDURE SP_LOCK_Row (IDRow IN INTEGER) IS BEGIN SELECT * FROM TBLTable WHERE IDRow = IDRow FOR UPDATE; END; The problem is that I keep getting the error: PLS-00428: an INTO clause is expected in this SELECT statement. Is there a way for me to lock the row without actually having to return a result set back to the client? The SQL Server equivalent is: CREATE PROCEDURE dbo.SP_LOCK_Row( @IDRow INT) AS SELECT * FROM dbo.TBLTable WITH (UPDLOCK, ROWLOCK) WHERE IDRow = @IDRow Tks

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  • MEF GetExports<T, TMetaDataView> returning nothing with AllowMultiple = True

    - by sohum
    I don't understand MEF very well, so hopefully this is a simple fix of how I think it works. I'm trying to use MEF to get some information about a class and how it should be used. I'm using the Metadata options to try to achieve this. My interfaces and attribute looks like this: public interface IMyInterface { } public interface IMyInterfaceInfo { Type SomeProperty1 { get; } double SomeProperty2 { get; } string SomeProperty3 { get; } } [MetadataAttribute] [AttributeUsage(AttributeTargets.Class, AllowMultiple = true)] public class ExportMyInterfaceAttribute : ExportAttribute, IMyInterfaceInfo { public ExportMyInterfaceAttribute(Type someProperty1, double someProperty2, string someProperty3) : base(typeof(IMyInterface)) { SomeProperty1 = someProperty1; SomeProperty2 = someProperty2; SomeProperty3 = someProperty3; } public Type SomeProperty1 { get; set; } public double SomeProperty2 { get; set; } public string SomeProperty3 { get; set; } } The class that is decorated with the attribute looks like this: [ExportMyInterface(typeof(string), 0.1, "whoo data!")] [ExportMyInterface(typeof(int), 0.4, "asdfasdf!!")] public class DecoratedClass : IMyInterface { } The method that is trying to use the import looks like this: private void SomeFunction() { // CompositionContainer is an instance of CompositionContainer var myExports = CompositionContainer.GetExports<IMyInterface, IMyInterfaceInfo>(); } In my case myExports is always empty. In my CompositionContainer, I have a Part in my catalog that has two ExportDefinitions, both with the following ContractName: "MyNamespace.IMyInterface". The Metadata is also loaded correctly per my exports. If I remove the AllowMultiple setter and only include one exported attribute, the myExports variable now has the single export with its loaded metadata. What am I doing wrong?

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  • c++ connect() keeps returning WSATIMEDOUT over internet but not localy

    - by KaiserJohaan
    Hello, For some reason, my chat application always gets WSATIMEDOUT when trying to connect to another person over the internet. int len_ip = GetWindowTextLength(GetDlgItem(hWnd,ID_EDIT_IP)); char ipBuffer[16]; SendMessage(GetDlgItem(hWnd,ID_EDIT_IP),WM_GETTEXT,16,(LPARAM)ipBuffer); long host_ip = inet_addr(ipBuffer); int initializeConnection(long host_ip, HWND hWnd) { // initialize winsock WSADATA wdata; int result = WSAStartup(MAKEWORD(2,2),&wdata); if (result != 0) { return 0; } // setup socket tcp_sock = socket(AF_INET,SOCK_STREAM,IPPROTO_TCP); if (tcp_sock == INVALID_SOCKET) { return 0; } // setup socket address SOCKADDR_IN tcp_sock_addr; tcp_sock_addr.sin_family = AF_INET; tcp_sock_addr.sin_port = SERVER_TCP_PORT; tcp_sock_addr.sin_addr.s_addr = host_ip; // connect to server if (connect(tcp_sock,(SOCKADDR*)&tcp_sock_addr,sizeof(tcp_sock_addr)) == SOCKET_ERROR) { return 0; } HRESULT hr = WSAGetLastError(); // set socket in asynchronous mode if (WSAAsyncSelect(tcp_sock,hWnd,SOCKET_TCP, FD_READ | FD_WRITE | FD_CONNECT | FD_CLOSE) == SOCKET_ERROR) { return 0; } return 1; } For some reason it works perfectly fine on local network between computers, but totally screws up over the internet. WSATIMEDOUT is always returned (not connection refused, so its not a port problem). It makes me believe something is wrong with the IP but why on earth can it work on local addresses (like 192.168.2.4) Any ideas? Cheers

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  • Method not returning string value c# <List>

    - by Santii20
    public List<string> Test_IsDataLoaded() { try { if (GRIDTest.Rows.Count != 0) { int countvalue = GRIDTest.Rows.Count; GRIDTest.Rows[0].WaitForControlReady(); List<string> ReleaseIDList = new List<string>(); int nCellCount = GRIDTest.Cells.Count; for(int nCount = 0;nCount<nCellCount ;nCount++) { if(nCount %5==0) ReleaseIDList.Add((GRIDTest.Cells[0].GetProperty("Value").ToString())); } return ReleaseIDList; } } catch (Exception) { } } Method throws me error = Not all code path return a value. Whats wrong in code.

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  • Mysqli prepared insert statements always returning false

    - by user1754679
    I'm writing prepared statements that are supposed to insert data into a table, on a database that's been pre-selected in the variable $GLOBALS['mysqli']. The connection has been tested, and that's not the problem I'm having. I'm only running into trouble whenever my prepared statement involves INSERT INTO. I know the tablename, and field names are correct, but $stmt is ALWAYS false. What gives? $stmt = $GLOBALS['mysqli']->prepare("INSERT INTO audit_RefreshCount (user, count, lastrefresh) values (?,?,?)"); if ($stmt == TRUE) { $stmt->bindParam('ssi', $_SESSION['username'], '0', time()); //$stmt->bind_Param('ssi', $_SESSION['username'], '0', time()); // Also doesn't work. $stmt->execute(); }

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