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  • C++ design question, container of instances and pointers

    - by Tom
    Hi all, Im wondering something. I have class Polygon, which composes a vector of Line (another class here) class Polygon { std::vector<Line> lines; public: const_iterator begin() const; const_iterator end() const; } On the other hand, I have a function, that calculates a vector of pointers to lines, and based on those lines, should return a pointer to a Polygon. Polygon* foo(Polygon& p){ std::vector<Line> lines = bar (p.begin(),p.end()); return new Polygon(lines); } Here's the question: I can always add a Polygon (vector Is there a better way that dereferencing each element of the vector and assigning it to the existing vector container? //for line in vector<Line*> v //vcopy is an instance of vector<Line> vcopy.push_back(*(v.at(i)) I think not, but I dont really like that approach. Hopefully, I will be able to convince the author of the class to change it, but I cant base my coding right now to that fact (and i'm scared of a performance hit). Thanks in advance.

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  • c++ specialized overload?

    - by acidzombie24
    -edit- i am trying to close the question. i solved the problem with boost::is_base_and_derived In my class i want to do two things. 1) Copy int, floats and other normal values 2) Copy structs that supply a special copy function (template T copyAs(); } the struct MUST NOT return int's unless i explicitly say ints. I do not want the programmer mistaking the mistake by doing int a = thatClass; -edit- someone mention classes dont return anything, i mean using the operator Type() overload. How do i create my copy operator in such a way i can copy both 1) ints, floats etc and the the struct restricted in the way i mention in 2). i tried doing template <class T2> T operator = (const T2& v); which would cover my ints, floats etc. But how would it differentiate from structs? so i wrote T operator = (const SomeGenericBase& v); The idea was the GenericBase would be unsed instead then i can do v.Whatever. But that backfires bc the functions i want wouldnt exist, unless i use virtual, but virtual templates dont exist. Also i would hate to use virtual I think the solution is to get rid of ints and have it convert to something that can do .as(). So i wrote something up but now i have the same problem, how does that differentiate ints and structs that have the .as() function template?

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  • VC9 C1083 Cannot open include file: 'boost...' after trying to abstract an include dependency

    - by ronivek
    Hey, So I've been working on a project for the past number of weeks and it uses a number of Boost libraries. In particular I'm using the boost::dynamic_bitset library quite extensively. I've had zero issues up until now; but tonight I discovered a dependency between some includes which I had to resolve; and I tried to do so by providing an abstract callback class. Effectively I now have the following: First include... class OtherClassCallback { public: virtual int someOtherMethod() const = 0; }; class SomeClass { public: void someMethod(OtherClassCallback *oc) { ... oc->someOtherMethod(); ... } }; Second include... #include "SomeClass.h" class SomeOtherClass : public OtherClassCallback { public: int someOtherMethod() const { return this->someInt; } }; Here is the issue; ever since I implemented this class I'm now getting the following error: fatal error C1083: Cannot open include file: 'boost/dynamic_bitset/dynamic_bitset.hpp': No such file or directory Now I'm getting no other compiler errors; and it's a pretty substantial project. My include paths and so on are perfect; my files are fully accessible and removing the changes fixes the issue. Does anyone have any idea what might be going on? I'm compiling to native Windows executables in VS9. I should confess that I'm very inexperienced with C++ in general so go easy on me if it's something horribly straightforward; I can't figure it out.

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  • overloading "<<" with a struct (no class) cout style

    - by monkeyking
    I have a struct that I'd like to output using either 'std::cout' or some other output stream. Is this possible without using classes? Thanks #include <iostream> #include <fstream> template <typename T> struct point{ T x; T y; }; template <typename T> std::ostream& dump(std::ostream &o,point<T> p) const{ o<<"x: " << p.x <<"\ty: " << p.y <<std::endl; } template<typename T> std::ostream& operator << (std::ostream &o,const point<T> &a){ return dump(o,a); } int main(){ point<double> p; p.x=0.1; p.y=0.3; dump(std::cout,p); std::cout << p ;//how? return 0; } I tried different syntax' but I cant seem to make it work.

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  • Handling Apache Thrift list/map Return Types in C++

    - by initzero
    First off, I'll say I'm not the most competent C++ programmer, but I'm learning, and enjoying the power of Thrift. I've implemented a Thrift Service with some basic functions that return void, i32, and list. I'm using a Python client controlled by a Django web app to make RPC calls and it works pretty well. The generated code is pretty straight forward, except for list returns: namespace cpp Remote enum N_PROTO { N_TCP, N_UDP, N_ANY } service Rcon { i32 ping() i32 KillFlows() i32 RestartDispatch() i32 PrintActiveFlows() i32 PrintActiveListeners(1:i32 proto) list<string> ListAllFlows() } The generated signatures from Rcon.h: int32_t ping(); int32_t KillFlows(); int32_t RestartDispatch(); int32_t PrintActiveFlows(); int32_t PrintActiveListeners(const int32_t proto); int64_t ListenerBytesReceived(const int32_t id); void ListAllFlows(std::vector<std::string> & _return); As you see, the ListAllFlows() function generated takes a reference to a vector of strings. I guess I expect it to return a vector of strings as laid out in the .thrift description. I'm wondering if I am meant to provide the function a vector of strings to modify and then Thrift will handle returning it to my client despite the function returning void. I can find absolutely no resources or example usages of Thrift list< types in C++. Any guidance would be appreciated.

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  • C++ Template problem adding two data types

    - by Sara
    I have a template class with an overloaded + operator. This is working fine when I am adding two ints or two doubles. How do I get it to add and int and a double and return the double? template <class T> class TemplateTest { private: T x; public: TemplateTest<T> operator+(const TemplateTest<T>& t1)const { return TemplateTest<T>(x + t1.x); } } in my main function i have void main() { TemplateTest intTt1 = TemplateTest<int>(2); TemplateTest intTt2 = TemplateTest<int>(4); TemplateTest doubleTt1 = TemplateTest<double>(2.1d); TemplateTest doubleTt2 = TemplateTest<double>(2.5d); std::cout << intTt1 + intTt2 << /n; std::cout << doubleTt1 + doubleTt2 << /n; } I want to be able to also do this std::cout << doubleTt1 + intTt2 << /n;

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  • Search string in file (C)

    - by chutsu
    So my code isn't working... test.c:27: warning: passing argument 1 of ‘search’ from incompatible pointer type which is the fgets line. My code opens a file, reads the file line by line, and I'm trying to create a "search" function that will return a value that indicates whether that string is found on that line of the file. My ultimate goal is to achieve a search and replace program. But one step at a time eh? this is what I have so far: #include <stdio.h> #include <string.h> int search(const char *content[], const char *search_term) { int t; for(t=0; content[t]; ++t){ if(!strcmp(content[t], search_term)){ return t; // found } } return 0; // not found } int main(int argc, char *argv[]) { FILE *file; char line[BUFSIZ]; int linenumber=0; char term[20] = "hello world"; file = fopen(argv[1], "r"); if(file != NULL){ while(fgets(line, sizeof(line), file)){ if(search(line, term) != -1){ printf("Search Term Found!!\n"); } ++linenumber; } } else{ perror(argv[1]); } fclose(file); return 0; }

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  • Howcome some C++ functions with unspecified linkage build with C linkage?

    - by christoffer
    This is something that makes me fairly perplexed. I have a C++ file that implements a set of functions, and a header file that defines prototypes for them. When building with Visual Studio or MingW-gcc, I get linking errors on two of the functions, and adding an 'extern "C"' qualifier resolved the error. How is this possible? Header file, "some_header.h": // Definition of struct DEMO_GLOBAL_DATA omitted DWORD WINAPI ThreadFunction(LPVOID lpData); void WriteLogString(void *pUserData, const char *pString, unsigned long nStringLen); void CheckValid(DEMO_GLOBAL_DATA *pData); int HandleStart(DEMO_GLOBAL_DATA * pDAta, TCHAR * pLogFileName); void HandleEnd(DEMO_GLOBAL_DATA *pData); C++ file, "some_implementation.cpp" #include "some_header.h" DWORD WINAPI ThreadFunction(LPVOID lpData) { /* omitted */ } void WriteLogString(void *pUserData, const char *pString, unsigned long nStringLen) { /* omitted */ } void CheckValid(DEMO_GLOBAL_DATA *pData) { /* omitted */ } int HandleStart(DEMO_GLOBAL_DATA * pDAta, TCHAR * pLogFileName) { /* omitted */ } void HandleEnd(DEMO_GLOBAL_DATA *pData) { /* omitted */ } The implementations compile without warnings, but when linking with the UI code that calls these, I get a normal error LNK2001: unresolved external symbol "int __cdecl HandleStart(struct _DEMO_GLOBAL_DATA *, wchar_t *) error LNK2001: unresolved external symbol "void __cdecl CheckValid(struct _DEMO_MAIN_GLOBAL_DATA * What really confuses me, now, is that only these two functions (HandleStart and CheckValid) seems to be built with C linkage. Explicitly adding "extern 'C'" declarations for only these two resolved the linking error, and the application builds and runs. Adding "extern 'C'" on some other function, such as HandleEnd, introduces a new linking error, so that one is obviously compiled correctly. The implementation file is never modified in any of this, only the prototypes.

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  • std::stringstream GCC Abnormal Behavior

    - by FlorianZ
    I have a very interesting problem with compiling a short little program on a Mac (GCC 4.2). The function below would only stream chars or strings into the stringstream, but not anything else (int, double, float, etc.) In fact, the fail flag is set if I attempt to convert for example an int into a string. However, removing the preprocessor flag: _GLIBCXX_DEBUG=1, which is set by default in XCode for the debug mode, will yield the desired results / correct behavior. Here is the simple function I am talking about. value is template variable of type T. Tested for int, double, float (not working), char and strings (working). template < typename T > const std::string Attribute<T>::getValueAsString() const { std::ostringstream stringValue; stringValue << value; return stringValue.str(); } Any ideas what I am doing wrong, why this doesn't work, or what the preprocessor flag does to make this not work anymore? Thanks!

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  • C++: Copy contructor: Use Getters or access member vars directly?

    - by cbrulak
    Have a simple container class: public Container { public: Container() {} Container(const Container& cont) //option 1 { SetMyString(cont.GetMyString()); } //OR Container(const Container& cont) //option 2 { m_str1 = cont.m_str1; } public string GetMyString() { return m_str1;} public void SetMyString(string str) { m_str1 = str;} private: string m_str1; } So, would you recommend this method or accessing the member variables directly? In the example, all code is inline, but in our real code there is no inline code. Update (29 Sept 09): Some of these answers are well written however they seem to get missing the point of this question: this is simple contrived example to discuss using getters/setters vs variables initializer lists or private validator functions are not really part of this question. I'm wondering if either design will make the code easier to maintain and expand. Some ppl are focusing on the string in this example however it is just an example, imagine it is a different object instead. I'm not concerned about performance. we're not programming on the PDP-11

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  • What is the purpose of the QAbstractButton::checkStateSet() method?

    - by darkadept
    I'm writing my own 4 state button and I'm not quite sure what to put in the checkStateSet() method, if anything. Here is what I've got so far: SyncDirectionButton::SyncDirectionButton(QWidget *parent) : QAbstractButton(parent) { setCheckable(true); setToolTip(tr("Click to change the sync direction")); _state = NoSync; } void SyncDirectionButton::paintEvent(QPaintEvent *e) { static QPixmapCache::Key noneKey; static QPixmapCache::Key bothKey; static QPixmapCache::Key leftKey; static QPixmapCache::Key rightKey; QPainter p(this); QPixmap pix; if (checkState() == SyncLeft) { if (!QPixmapCache::find(leftKey, &pix)) { pix.load(":/icons/sync-left.png"); leftKey = QPixmapCache::insert(pix); } } else if (checkState() == SyncBoth) { if (!QPixmapCache::find(rightKey, &pix)) { pix.load(":/icons/sync-right.png"); rightKey = QPixmapCache::insert(pix); } } else if (checkState() == SyncRight) { if (!QPixmapCache::find(bothKey, &pix)) { pix.load(":/icons/sync-both.png"); bothKey = QPixmapCache::insert(pix); } } else if (checkState() == NoSync) { if (!QPixmapCache::find(noneKey, &pix)) { pix.load(":/icons/application-exit.png"); noneKey = QPixmapCache::insert(pix); } } p.drawPixmap(0,0,pix); } SyncDirectionButton::DirectionState SyncDirectionButton::checkState() const { return _state; } void SyncDirectionButton::setCheckState(DirectionState state) { setChecked(state != NoSync); if (state != _state) { _state = state; } } QSize SyncDirectionButton::sizeHint() const { return QSize(180,90); } void SyncDirectionButton::checkStateSet() { } void SyncDirectionButton::nextCheckState() { setCheckState((DirectionState)((checkState()+1)%4)); }

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  • Clicking the mouse down to drag objects on Mac

    - by Uri
    I've been using the following code to issue clicks programmatically on a Mac void PostMouseEvent(CGMouseButton button, CGEventType type, const CGPoint point) { CGEventRef theEvent = CGEventCreateMouseEvent(NULL, type, point, button); CGEventSetType(theEvent, type); CGEventPost(kCGHIDEventTap, theEvent); CFRelease(theEvent); } void Click(const CGPoint point) { PostMouseEvent(kCGMouseButtonLeft, kCGEventMouseMoved, point); NSLog(@"Click!"); PostMouseEvent(kCGMouseButtonLeft, kCGEventLeftMouseDown, point); PostMouseEvent(kCGMouseButtonLeft, kCGEventLeftMouseUp, point); } Now, I'm trying to click down to be able to drag objects, like a scroll bar or an application's window. I'm using the following: PostMouseEvent(kCGMouseButtonLeft, kCGEventMouseMoved, point); NSLog(@"Click Down!"); PostMouseEvent(kCGMouseButtonLeft, kCGEventLeftMouseDown, point); When i ran the code above something interesting will happen, when the left mouse down is issue nothing seem to happen, I move my mouse and the window doesn't move, however when I added a mouse up event then the window jumped to the location where I supposedly dragged it. this is sort of OK, however, how do I can make the mouse click down and drag an object? Note: I do have a whole method to see when the mouse stopped moving so I can click up. please post code. Thanks

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  • How to Populate a 'Tree' structure 'Declaratively'

    - by mackenir
    I want to define a 'node' class/struct and then declare a tree of these nodes in code in such a way that the way the code is formatted reflects the tree structure, and there's not 'too much' boiler plate in the way. Note that this isn't a question about data structures, but rather about what features of C++ I could use to arrive at a similar style of declarative code to the example below. Possibly with C++0X this would be easier as it has more capabilities in the area of constructing objects and collections, but I'm using Visual Studio 2008. Example tree node type: struct node { string name; node* children; node(const char* name, node* children); node(const char* name); }; What I want to do: Declare a tree so its structure is reflected in the source code node root = node("foo", [ node("child1"), node("child2", [ node("grand_child1"), node("grand_child2"), node("grand_child3" ]), node("child3") ]); NB: what I don't want to do: Declare a whole bunch of temporary objects/colls and construct the tree 'backwards' node grandkids[] = node[3] { node("grand_child1"), node("grand_child2"), node("grand_child3" }; node kids[] = node[3] { node("child1"), node("child2", grandkids) node("child3") }; node root = node("foo", kids);

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  • Compile C++ in Visual Studio

    - by Kasun
    Hi All.. I use this method to compile C++ file in VS. But even i provide the correct file it returns false. Can any one help me... This is class called CL class CL { private const string clexe = @"cl.exe"; private const string exe = "Test.exe", file = "test.cpp"; private string args; public CL(String[] args) { this.args = String.Join(" ", args); this.args += (args.Length > 0 ? " " : "") + "/Fe" + exe + " " + file; } public Boolean Compile(String content, ref string errors) { if (File.Exists(exe)) File.Delete(exe); if (File.Exists(file)) File.Delete(file); File.WriteAllText(file, content); Process proc = new Process(); proc.StartInfo.UseShellExecute = false; proc.StartInfo.RedirectStandardOutput = true; proc.StartInfo.RedirectStandardError = true; proc.StartInfo.FileName = clexe; proc.StartInfo.Arguments = this.args; proc.StartInfo.CreateNoWindow = true; proc.Start(); //errors += proc.StandardError.ReadToEnd(); errors += proc.StandardOutput.ReadToEnd(); proc.WaitForExit(); bool success = File.Exists(exe); return success; } } This is my button click event private void button1_Click(object sender, EventArgs e) { string content = "#include <stdio.h>\nmain(){\nprintf(\"Hello world\");\n}\n"; string errors = ""; CL k = new CL(new string[] { }); if (k.Compile(content, ref errors)) Console.WriteLine("Success!"); else MessageBox.Show("Errors are : ", errors); }

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  • streaming xml pretty printer in C/C++ using expat or libxml2?

    - by Mark Zeren
    I have a library that outputs xml without whitespace all on one line. In some cases I'd like to pretty print that output. I'm looking for a BSD-ish licensed C/C++ library or sample code that will take a raw xml byte stream and pretty print it. Here's some pseudo code showing one way that I might use this functionality: void my_write(const char* buf, int len); PrettyPrinter pp(bind(&my_write)); while (...) { // ... get some more xml ... const char* buf = xmlSource.get_buf(); int len = xmlSource.get_buf_len(); int written = pp.write(buf, len); // calls my_write with pretty printed xml // ... error handling, maybe call write again, etc. ... } I'd like to avoid instantiating a DOM representation. I already have dependencies on the expat and libxml2 shared libraries, and I'd rather not add any more shared library dependencies.

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  • How to support comparisons for QVariant objects containing a custom type?

    - by Tyler McHenry
    According to the Qt documentation, QVariant::operator== does not work as one might expect if the variant contains a custom type: bool QVariant::operator== ( const QVariant & v ) const Compares this QVariant with v and returns true if they are equal; otherwise returns false. In the case of custom types, their equalness operators are not called. Instead the values' addresses are compared. How are you supposed to get this to behave meaningfully for your custom types? In my case, I'm storing an enumerated value in a QVariant, e.g. In a header: enum MyEnum { Foo, Bar }; Q_DECLARE_METATYPE(MyEnum); Somewhere in a function: QVariant var1 = QVariant::fromValue<MyEnum>(Foo); QVariant var2 = QVariant::fromValue<MyEnum>(Foo); assert(var1 == var2); // Fails! What do I need to do differently in order for this assertion to be true? I understand why it's not working -- each variant is storing a separate copy of the enumerated value, so they have different addresses. I want to know how I can change my approach to storing these values in variants so that either this is not an issue, or so that they do both reference the same underlying variable. It don't think it's possible for me to get around needing equality comparisons to work. The context is that I am using this enumeration as the UserData in items in a QComboBox and I want to be able to use QComboBox::findData to locate the item index corresponding to a particular enumerated value.

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  • C++ compiler unable to find function (namespace related)

    - by CS student
    I'm working in Visual Studio 2008 on a C++ programming assignment. We were supplied with files that define the following namespace hierarchy (the names are just for the sake of this post, I know "namespace XYZ-NAMESPACE" is redundant): (MAIN-NAMESPACE){ a bunch of functions/classes I need to implement... (EXCEPTIONS-NAMESPACE){ a bunch of exceptions } (POINTER-COLLECTIONS-NAMESPACE){ Set and LinkedList classes, plus iterators } } The MAIN-NAMESPACE contents are split between a bunch of files, and for some reason which I don't understand the operator<< for both Set and LinkedList is entirely outside of the MAIN-NAMESPACE (but within Set and LinkedList's header file). Here's the Set version: template<typename T> std::ostream& operator<<(std::ostream& os, const MAIN-NAMESPACE::POINTER-COLLECTIONS-NAMESPACE::Set<T>& set) Now here's the problem: I have the following data structure: Set A Set B Set C double num It's defined to be in a class within MAIN-NAMESPACE. When I create an instance of the class, and try to print one of the sets, it tells me that: error C2679: binary '<<' : no operator found which takes a right-hand operand of type 'const MAIN-NAMESPACE::POINTER-COLLECTIONS-NAMESPACE::Set' (or there is no acceptable conversion) However, if I just write a main() function, and create Set A, fill it up, and use the operator- it works. Any idea what is the problem? (note: I tried any combination of using and include I could think of).

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  • insert data using sqlite issue on iphone ( not reflecting on table)

    - by prajakta
    i can insert my data but i cant show them on my table view ..i did [tableview reload data] but of no success here is my code -(void)gButtonTapped:(id)sender { NSLog(@"right nav bar button is hit%@ ",storePaths); //[self readAnimalsFromDatabase2]; appDelegate = (DatabaseTestAppDelegate *)[[UIApplication sharedApplication] delegate]; sqlite3 *database; sqlite3_stmt *compiled_statement1; if(sqlite3_open([storePaths UTF8String], &database) == SQLITE_OK) { //const char *sqlStatement = NSString *newQuery = [NSString stringWithFormat:@"insert into cat_tbl (cat_id,names,imgs) values ('12','test1','r.png')"]; // NSString *newQuery = [NSString stringWithFormat:@"select * from list_tbl"]; const char *sql = [newQuery cStringUsingEncoding:NSASCIIStringEncoding]; NSLog(@"update query is %@",newQuery); if(sqlite3_prepare_v2(database, sql, -1, &compiled_statement1, NULL) == SQLITE_OK) { int result = sqlite3_step(compiled_statement1); sqlite3_reset(compiled_statement1); NSLog(@"result %d", result); if(result != SQLITE_ERROR) { int lastInsertId = sqlite3_last_insert_rowid(database); NSLog(@"x %d", lastInsertId); } } } sqlite3_finalize(compiled_statement1); sqlite3_close(database); [tabelView reloadData];// this is also not working }

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  • When is a bool not a bool (compiler warning C4800)

    - by omatai
    Consider this being compiled in MS Visual Studio 2005 (and probably others): CPoint point1( 1, 2 ); CPoint point2( 3, 4 ); const bool point1And2Identical( point1 == point2 ); // C4800 warning const bool point1And2TheSame( ( point1 == point2 ) == TRUE ); // no warning What the...? Is the MSVC compiler brain-dead? As far as I can tell, TRUE is #defined as 1, without any type information. So by what magic is there any difference between these two lines? Surely the type of the expression inside the brackets is the same in both cases? [This part of the question now satisfactorily answered in the comments just below] Personally, I think that avoiding the warning by using the == TRUE option is ugly (though less ugly than the != 0 alternative, despite being more strictly correct), and it is better to use #pragma warning( disable:4800 ) to imply "my code is good, the compiler is an ass". Agree? Note - I have seen all manner of discussion on C4800 talking about assigning ints to bools, or casting a burger combo with large fries (hold the onions) to a bool, and wondering why there are strange results. I can't find a clear answer on what seems like a much simpler question... that might just shine line on C4800 in general.

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  • TFS2010 API - Which server event fires when checkin notes are changed?

    - by user3708981
    I've written a TFS plugin that impliments the ISubscribe interface, and creates an external ticket base off of the contents of a check-in note. What I would like to do, if when I go back through older TFS check-ins in VS and edit a check-in note, the plugin would process that event and create an external ticket retroactively. What event / SubscribedType do I need to subscribe to in order for ProcessEvents to fire? My stubbed out code - using Microsoft.TeamFoundation.Client; using Microsoft.TeamFoundation.Common; using Microsoft.TeamFoundation.VersionControl.Client; // From C:\Program Files\Microsoft Team Foundation Server 2010\Tools\ using Microsoft.TeamFoundation.Framework.Server; using Microsoft.TeamFoundation.VersionControl.Server; using Changeset = Microsoft.TeamFoundation.VersionControl.Server.Changeset; public class EmbeddedWorkItemEventHandler : ISubscriber { const string EVENT_NAME = "TicketEvent"; const string APP_LOG = "Application"; public Type[] SubscribedTypes() { return new Type[1] { typeof(CheckinNotification) }; // What else do I need here? } public string Name { get { return EVENT_NAME; } } public SubscriberPriority Priority { get { return SubscriberPriority.Normal; } } public EventNotificationStatus ProcessEvent(TeamFoundationRequestContext requestContext, NotificationType notificationType, object notificationEventArgs, out int statusCode, out string statusMessage, out ExceptionPropertyCollection properties) { // Create the event source, if it doesn't exist if (!System.Diagnostics.EventLog.SourceExists(EVENT_NAME)) { System.Diagnostics.EventLog.CreateEventSource(EVENT_NAME, APP_LOG); } statusCode = 0; properties = null; statusMessage = String.Empty; string ErrorLine = ""; try { // Here we'll validate the Ticket name if (notificationType == NotificationType.DecisionPoint && notificationEventArgs is CheckinNotification) { //Check-in blocking logic here. } else if (notificationType == NotificationType.Notification && notificationEventArgs is CheckinNotification) { // Tickets on check-in here. } } Catch { // Error checking } return EventNotificationStatus.ActionPermitted; }

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  • Need advice on C++ coding pattern

    - by Kotti
    Hi! I have a working prototype of a game engine and right now I'm doing some refactoring. What I'm asking for is your opinion on usage of the following C++ coding patterns. I have implemented some trivial algorithms for collision detection and they are implemented the following way: Not shown here - class constructor is made private and using algorithms looks like Algorithm::HandleInnerCollision(...) struct Algorithm { // Private routines static bool is_inside(Point& p, Object& object) { // (...) } public: /** * Handle collision where the moving object should be always * located inside the static object * * @param MovingObject & mobject * @param const StaticObject & sobject * @return void * @see */ static void HandleInnerCollision(MovingObject& mobject, const StaticObject& sobject) { // (...) } So, my question is - somebody advised me to do it "the C++" way - so that all functions are wrapped in a namespace, but not in a class. Is there some good way to preserve privating if I will wrap them into a namespace as adviced? What I want to have is a simple interface and ability to call functions as Algorithm::HandleInnerCollision(...) while not polluting the namespace with other functions such as is_inside(...) Of, if you can advise any alternative design pattern for such kind of logics, I would really appreciate that...

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  • Preprocessor #define vs. function pointer - best practice?

    - by Dustin
    I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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  • Problem with SqlLite database in Qt SDK 1.0.2

    - by Risino
    Hi I have a problem with SqlLite database. Here is my code: void incomeDialog::on_add_pushButton_clicked() { int a = ui->income_lineEdit->text().toInt(); int b = ui->other_lineEdit->text().toInt(); int c = (a+b); db = QSqlDatabase::addDatabase("QSQLITE"); db.setDatabaseName("money.db"); QSqlQuery query(db); query.exec("create table Income" "(Month TEXT, Payment NUMBER, Other NUMBER, Together NUMBER)"); query.prepare("INSERT INTO Income values (?,?,?,?)"); query.addBindValue(ui->comboBox->currentText()); query.addBindValue(ui->income_lineEdit->text().toInt()); query.addBindValue(ui->other_lineEdit->text().toInt()); query.addBindValue(c); query.exec(); } I use qt sdk 1.0.2. After building shows errors: Undefined reference to 'QSqlDatabase::addDatabase(QString const&, QString const&)... all errors is similar (Undefined reference to 'QSqlDatabase:: Do you have any idea how to repair it?

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  • Convert Virtual Key Code to unicode string

    - by Joshua Weinberg
    I have some code I've been using to get the current keyboard layout and convert a virtual key code into a string. This works great in most situations, but I'm having trouble with some specific cases. The one that brought this to light is the accent key next to the backspace key on german QWERTZ keyboards. http://en.wikipedia.org/wiki/File:KB_Germany.svg That key generates the VK code I'd expect kVK_ANSI_Equal but when using a QWERTZ keyboard layout I get no description back. Its ending up as a dead key because its supposed to be composed with another key. Is there any way to catch these cases and do the proper conversion? My current code is below. TISInputSourceRef currentKeyboard = TISCopyCurrentKeyboardInputSource(); CFDataRef uchr = (CFDataRef)TISGetInputSourceProperty(currentKeyboard, kTISPropertyUnicodeKeyLayoutData); const UCKeyboardLayout *keyboardLayout = (const UCKeyboardLayout*)CFDataGetBytePtr(uchr); if(keyboardLayout) { UInt32 deadKeyState = 0; UniCharCount maxStringLength = 255; UniCharCount actualStringLength = 0; UniChar unicodeString[maxStringLength]; OSStatus status = UCKeyTranslate(keyboardLayout, keyCode, kUCKeyActionDown, 0, LMGetKbdType(), kUCKeyTranslateNoDeadKeysBit, &deadKeyState, maxStringLength, &actualStringLength, unicodeString); if(actualStringLength > 0 && status == noErr) return [[NSString stringWithCharacters:unicodeString length:(NSInteger)actualStringLength] uppercaseString]; }

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  • Where to add an overloaded operator for the tr1::array?

    - by phlipsy
    Since I need to add an operator& for the std::tr1::array<bool, N> I wrote the following lines template<std::size_t N> std::tr1::array<bool, N> operator& (const std::tr1::array<bool, N>& a, const std::tr1::array<bool, N>& b) { std::tr1::array<bool, N> result; std::transform(a.begin(), a.end(), b.begin(), result.begin(), std::logical_and<bool>()); return result; } Now I don't know in which namespace I've to put this function. I considered the std namespace as a restricted area. Only total specialization and overloaded function templates are allowed to be added by the user. Putting it into the global namespace isn't "allowed" either in order to prevent pollution of the global namespace and clashes with other declarations. And finally putting this function into the namespace of the project doesn't work since the compiler won't find it there. What had I best do? I don't want to write a new array class putted into the project namespace. Because in this case the compiler would find the right namespace via argument dependent name lookup. Or is this the only possible way because writing a new operator for existing classes means extending their interfaces and this isn't allowed either for standard classes?

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