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  • Object does not exist after constructor?

    - by openbas
    Hello, I have a constructor that looks like this (in c++): Interpreter::Interpreter() { tempDat == new DataObject(); tempDat->clear(); } the constructor of dataObject does absolutely nothing, and clear does this: bool DataObject::clear() { //clear the object if (current_max_id > 0) { indexTypeLookup.clear(); intData.clear(); doubleData.clear(); current_max_id = 0; } } Those members are defined as follows: std::map<int, int> indexTypeLookup; std::map<int, int> intData; std::map<int, double> doubleData; Now the strange thing is that I'm getting a segfault on tempDat-clear(); gdb says tempDat is null. How is that possible? The constructor of tempDat cannot fail, it looks like this: DataObject::DataObject() : current_max_id(0) { } I know there are probably better way's of making such a data structure, but I really like to know where this segfault problem is coming from..

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  • Constructor Overload Problem in C++ Inheritance

    - by metdos
    Here my code snippet: class Request { public: Request(void); ……….. } Request::Request(void) { qDebug()<<"Request: "<<"Hello World"; } class LoginRequest :public Request { public: LoginRequest(void); LoginRequest(QDomDocument); …………… } LoginRequest::LoginRequest(void) { qDebug()<<"LoginRequest: "<<"Hello World"; requestType=LOGIN; requestId=-1; } LoginRequest::LoginRequest(QDomDocument doc){ qDebug()<<"LoginRequest: "<<"Hello World with QDomDocument"; LoginRequest::LoginRequest(); xmlDoc_=doc; } When call constructor of Overrided LoginRequest LoginRequest *test=new LoginRequest(doc); I came up with this result: Request: Hello World LoginRequest: Hello World with QDomDocument Request: Hello World LoginRequest: Hello World Obviously both constructor of LoginRequest called REquest constructor. Is there any way to cape with this situation? I can construct another function that does the job I want to do and have both constructors call that function. But I wonder is there any solution?

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  • Constructor Overload Problem in C++ Inherrentance

    - by metdos
    Here my code snippet: class Request { public: Request(void); ……….. } Request::Request(void) { qDebug()<<"Request: "<<"Hello World"; } class LoginRequest :public Request { public: LoginRequest(void); LoginRequest(QDomDocument); …………… } LoginRequest::LoginRequest(void) { qDebug()<<"LoginRequest: "<<"Hello World"; requestType=LOGIN; requestId=-1; } LoginRequest::LoginRequest(QDomDocument doc){ qDebug()<<"LoginRequest: "<<"Hello World with QDomDocument"; LoginRequest::LoginRequest(); xmlDoc_=doc; } When call constructor of Overrided LoginRequest LoginRequest *test=new LoginRequest(doc); I came up with this result: Request: Hello World LoginRequest: Hello World with QDomDocument Request: Hello World LoginRequest: Hello World Obviously both constructor of LoginRequest called REquest constructor. Is there any way to cape with this situation? I can construct another function that does the job I want to do and have both constructors call that function. But I wonder is there any solution?

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  • C++ Constructor With Parameters Won't Initialize, Errors C2059 and C2228

    - by Some Girl
    I'm a C# programmer trying to muddle through C++ to create a Windows Forms Application. I have a Windows Form that makes use of a user-created class. Basically I'm trying to use a constructor that takes parameters, but my form won't let me initialize the object with parameter. Here's the code, hopefully somebody can explain the problem to me because I'm completely baffled... Here's my header file: BankAcct.h public ref class BankAcct { private: int money; public: BankAcct(); BankAcct(int); void Deposit(int); void GetBalance(int&); }; And my definition file: BankAcct.cpp #include "StdAfx.h" #include "BankAcct.h" BankAcct::BankAcct() { money = 0; } BankAcct::BankAcct(int startAmt) { money = startAmt; } void BankAcct::Deposit(int depAmt) { money += depAmt; } void BankAcct::GetBalance(int& balance) { balance = money; } And finally my main form. Won't copy the whole thing, of course, but I'm trying to declare the new bank account object, and start it with a balance of say $50. private: BankAcct myAccount(50); //does not work! WHY?? //private: //BankAcct myAccount; //works then in the form constructor my code is this: public: frmBank(void) { InitializeComponent(); int bal; myAccount.GetBalance(bal); lblBankBalance->Text += Convert::ToString(bal); } I've included the BankAcct.h file at the top of my frmBank.h, what else am I doing wrong here? It works great if I use the default constructor (the one that starts the bank balance at zero). I get the following error messages: error C2059: syntax error: 'constant' and error C2228: left of '.GetBalance' must have class/struct/union Thank you for any and all help on this one!!

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  • c++ STL vector is not acccepting the copy constructor

    - by prabhakaran
    I wrote a code ( c++,visual studio 2010) which is having a vector, even I though copy const is declared, but is still showing that copy const is not declared Here the code #include<iostream> #include<vector> using namespace std; class A { public: A(){cout << "Default A is acting" << endl ;} A(A &a){cout << "Copy Constructor of A is acting" << endl ;} }; int main() { A a; A b=a; vector<A> nothing; nothing.push_back(a); int n; cin >> n; } The error I got is Error 1 error C2558: class 'A' : no copy constructor available or copy constructor is declared 'explicit' c:\program files\microsoft visual studio 10.0\vc\include\xmemory 48 1 delete Anybody please help me

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  • Constructor ambiguous quesiton

    - by Crystal
    I'm trying to create a simple date class, but I get an error on my main file that says, "call of overloaded Date() is ambiguous." I'm not sure why since I thought as long as I had different parameters for my constructor, I was ok. Here is my code: header file: #ifndef DATE_H #define DATE_H using std::string; class Date { public: static const int monthsPerYear = 12; // num of months in a yr Date(int = 1, int = 1, int = 1900); // default constructor Date(); // uses system time to create object void print() const; // print date in month/day/year format ~Date(); // provided to confirm destruction order string getMonth(int month) const; // gets month in text format private: int month; // 1 - 12 int day; // 1 - 31 int year; // any year int checkDay(int) const; }; #endif .cpp file #include <iostream> #include <iomanip> #include <string> #include <ctime> #include "Date.h" using namespace std; Date::Date() { time_t seconds = time(NULL); struct tm* t = localtime(&seconds); month = t->tm_mon; day = t->tm_mday; year = t->tm_year; } Date::Date(int mn, int dy, int yr) { if (mn > 0 && mn <= monthsPerYear) month = mn; else { month = 1; // invalid month set to 1 cout << "Invalid month (" << mn << ") set to 1.\n"; } year = yr; // could validate yr day = checkDay(dy); // validate the day // output Date object to show when its constructor is called cout << "Date object constructor for date "; print(); cout << endl; } void Date::print() const { string str; cout << month << '/' << day << '/' << year << '\n'; // new code for HW2 cout << setfill('0') << setw(3) << day; // prints in ddd cout << " " << year << '\n'; // yyyy format str = getMonth(month); // prints in month (full word), day, year cout << str << " " << day << ", " << year << '\n'; } and my main.cpp #include <iostream> #include "Date.h" using std::cout; int main() { Date date1(4, 30, 1980); date1.print(); cout << '\n'; Date date2; date2.print(); }

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  • Ambiguous constructor call

    - by Crystal
    I'm trying to create a simple date class, but I get an error on my main file that says, "call of overloaded Date() is ambiguous." I'm not sure why since I thought as long as I had different parameters for my constructor, I was ok. Here is my code: header file: #ifndef DATE_H #define DATE_H using std::string; class Date { public: static const int monthsPerYear = 12; // num of months in a yr Date(int = 1, int = 1, int = 1900); // default constructor Date(); // uses system time to create object void print() const; // print date in month/day/year format ~Date(); // provided to confirm destruction order string getMonth(int month) const; // gets month in text format private: int month; // 1 - 12 int day; // 1 - 31 int year; // any year int checkDay(int) const; }; #endif .cpp file #include <iostream> #include <iomanip> #include <string> #include <ctime> #include "Date.h" using namespace std; Date::Date() { time_t seconds = time(NULL); struct tm* t = localtime(&seconds); month = t->tm_mon; day = t->tm_mday; year = t->tm_year; } Date::Date(int mn, int dy, int yr) { if (mn > 0 && mn <= monthsPerYear) month = mn; else { month = 1; // invalid month set to 1 cout << "Invalid month (" << mn << ") set to 1.\n"; } year = yr; // could validate yr day = checkDay(dy); // validate the day // output Date object to show when its constructor is called cout << "Date object constructor for date "; print(); cout << endl; } void Date::print() const { string str; cout << month << '/' << day << '/' << year << '\n'; // new code for HW2 cout << setfill('0') << setw(3) << day; // prints in ddd cout << " " << year << '\n'; // yyyy format str = getMonth(month); // prints in month (full word), day, year cout << str << " " << day << ", " << year << '\n'; } and my main.cpp #include <iostream> #include "Date.h" using std::cout; int main() { Date date1(4, 30, 1980); date1.print(); cout << '\n'; Date date2; date2.print(); }

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  • Need help with copy constructor for very basic implementation of singly linked lists

    - by Jesus
    Last week, we created a program that manages sets of strings, using classes and vectors. I was able to complete this 100%. This week, we have to replace the vector we used to store strings in our class with simple singly linked lists. The function basically allows users to declare sets of strings that are empty, and sets with only one element. In the main file, there is a vector whose elements are a struct that contain setName and strSet (class). HERE IS MY PROBLEM: It deals with the copy constructor of the class. When I remove/comment out the copy constructor, I can declare as many empty or single sets as I want, and output their values without a problem. But I know I will obviously need the copy constructor for when I implement the rest of the program. When I leave the copy constructor in, I can declare one set, either single or empty, and output its value. But if I declare a 2nd set, and i try to output either of the first two sets, i get a Segmentation Fault. Moreover, if i try to declare more then 2 sets, I get a Segmentation Fault. Any help would be appreciated!! Here is my code for a very basic implementation of everything: Here is the setcalc.cpp: (main file) #include <iostream> #include <cctype> #include <cstring> #include <string> #include "help.h" #include "strset2.h" using namespace std; // Declares of structure to hold all the sets defined struct setsOfStr { string nameOfSet; strSet stringSet; }; // Checks if the set name inputted is unique bool isSetNameUnique( vector<setsOfStr> strSetArr, string setName) { for(unsigned int i = 0; i < strSetArr.size(); i++) { if( strSetArr[i].nameOfSet == setName ) { return false; } } return true; } int main(int argc, char *argv[]) { char commandChoice; // Declares a vector with our declared structure as the type vector<setsOfStr> strSetVec; string setName; string singleEle; // Sets a loop that will constantly ask for a command until 'q' is typed while (1) { // declaring a set to be empty if(commandChoice == 'd') { cin >> setName; // Check that the set name inputted is unique if (isSetNameUnique(strSetVec, setName) == true) { strSet emptyStrSet; setsOfStr set1; set1.nameOfSet = setName; set1.stringSet = emptyStrSet; strSetVec.push_back(set1); } else { cerr << "ERROR: Re-declaration of set '" << setName << "'\n"; } } // declaring a set to be a singleton else if(commandChoice == 's') { cin >> setName; cin >> singleEle; // Check that the set name inputted is unique if (isSetNameUnique(strSetVec, setName) == true) { strSet singleStrSet(singleEle); setsOfStr set2; set2.nameOfSet = setName; set2.stringSet = singleStrSet; strSetVec.push_back(set2); } else { cerr << "ERROR: Re-declaration of set '" << setName << "'\n"; } } // using the output function else if(commandChoice == 'o') { cin >> setName; if(isSetNameUnique(strSetVec, setName) == false) { // loop through until the set name is matched and call output on its strSet for(unsigned int k = 0; k < strSetVec.size(); k++) { if( strSetVec[k].nameOfSet == setName ) { (strSetVec[k].stringSet).output(); } } } else { cerr << "ERROR: No such set '" << setName << "'\n"; } } // quitting else if(commandChoice == 'q') { break; } else { cerr << "ERROR: Ignoring bad command: '" << commandChoice << "'\n"; } } return 0; } Here is the strSet2.h: #ifndef _STRSET_ #define _STRSET_ #include <iostream> #include <vector> #include <string> struct node { std::string s1; node * next; }; class strSet { private: node * first; public: strSet (); // Create empty set strSet (std::string s); // Create singleton set strSet (const strSet &copy); // Copy constructor // will implement destructor later void output() const; strSet& operator = (const strSet& rtSide); // Assignment }; // End of strSet class #endif // _STRSET_ And here is the strSet2.cpp (implementation of class) #include <iostream> #include <vector> #include <string> #include "strset2.h" using namespace std; strSet::strSet() { first = NULL; } strSet::strSet(string s) { node *temp; temp = new node; temp->s1 = s; temp->next = NULL; first = temp; } strSet::strSet(const strSet& copy) { cout << "copy-cst\n"; node *n = copy.first; node *prev = NULL; while (n) { node *newNode = new node; newNode->s1 = n->s1; newNode->next = NULL; if (prev) { prev->next = newNode; } else { first = newNode; } prev = newNode; n = n->next; } } void strSet::output() const { if(first == NULL) { cout << "Empty set\n"; } else { node *temp; temp = first; while(1) { cout << temp->s1 << endl; if(temp->next == NULL) break; temp = temp->next; } } } strSet& strSet::operator = (const strSet& rtSide) { first = rtSide.first; return *this; }

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  • Using named pipes in Rails

    - by FancyDancy
    I need to read and write some data through named pipes. I have tested it in a simple Ruby app, and it works nice. But I dont know, where should i put it in my Rails app? I have heard about Rake tasks, but i don't sure, is it right solution. I need to open a pipe-file, and listen to data. If there is any, i need to process it and make a DB-query. Then, write some data to another pipe. I know, how it works, but the only problem - how to run it with Rails? Give me some examples, please.

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  • Connecting Named SQL Server Express 2005 from MySQL Migration Toolkit 1.1.10

    - by KoolKabin
    Hi guys, I am trying to migrate SQL Server Express 2005 database to mysql. I came across the mysql migration toolkit. When i started with the tool it asked for my sql server express information. I provided all the information of the sql express but it still can't connect. My machine has got 1.) SQL Server 2000 [Default instance eg computername ] 2.) SQL Server Express 2005 [Default Named Instance eg computername$SQLExpress ] *I can make easy connection from Microsoft SQL Server Management Studio. I am getting problem only while connecting from MySQl Migration toolkit 1.1.10

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  • Web service can't open named pipe - access denied

    - by Patrick
    Hi All, I've got a C++ service which provides a named pipe to clients with a NULL SECURITY_ATTRIBUTES as follows: hPipe = CreateNamedPipe( lpszPipename, PIPE_ACCESS_DUPLEX | FILE_FLAG_OVERLAPPED, PIPE_TYPE_BYTE | PIPE_READMODE_BYTE | PIPE_WAIT, PIPE_UNLIMITED_INSTANCES, BUFSIZE, BUFSIZE, 0, NULL); There is a dll which uses this pipe to get services. There is a c# GUI which uses the dll and works fine. There is a .net web site which also uses this dll (the exact same one on the same PC) but always gets permission denied when it tries to open the pipe. Any one know why this might happen and how to fix it? Also does anyone know of a good tutorial on SECURITY_ATTRIBUTES because I haven't understood the msdn info yet. Thanks, Patrick

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  • compiler warning on (ambiguous) method resolution with named parameters

    - by FireSnake
    One question regarding whether the following code should yield a compiler warning or not (it doesn't). It declares two methods of the same name/return type, one has an additional named/optional parameter with default value. NOTE: technically the resolution isn't ambiguous, because the rules clearly state that the first method will get called. See here, Overload resolution, third bullet point. This behavior is also intuitive to me, no question. public void Foo(int arg) { ... } public void Foo(int arg, bool bar = true) { ...} Foo(42); // shouldn't this give a compiler warning? I think a compiler warning would be kind of intuitive here. Though the code technically is clean (whether it is a sound design is a different question:)).

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  • Update access table rst with named cell values from excel

    - by uZI
    I have got a table in access that I loop through using a DAO recordset. For every recordset I take a bunch of data to an excel spreadsheet and run it through a model in excel. This produces a bunch of results in excel which are calculated in named cells. I want to be able to update the current recordset in access with these results but am having a tough time doing it. I have the following code code to create a DAO recordset code to move to first record code to parse data to excel code to run a bunch of stuff in excel including a goal seek to calculate results next I use the follwoing code without success With MyXL strSQL = "UPDATE ProductPricing SET Profit = " & .Names("Profit") & ";" End With Code to move to next record and loop until EOF any help is appreciated thanks

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  • How to use prepared statements (named parameters) on a php Class

    - by Mohamed Adib Errifai
    This is my first post here. I've searched in the site, but inforutunaly no matchs. Anyway, i want to know how to use named parameters on a class. so the pdo basic form is something like. $query = $bdd->prepare('SELECT * FROM table WHERE login = :login AND pww = :pww'); $query->execute(array('login' => $login, 'pww' => $pww)); and i want to integrate this on a class regardless of the number of parameters. Currently, i have this code http://pastebin.com/kKgSkaKt and for parameters, i use somethings like ( which is wrong and vulnerable to injection ) require_once 'classes/Mysql.class.php'; $mysql = new Mysql(); $sql = 'SELECT * FROM articles WHERE id = '.$_GET['id'].' LIMIT 1'; $data = $mysql->select($sql); And Thanks.

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  • Accessing the constructor by using Reflection

    - by Md. Rashim Uddin
    Assume the class is public and and the constructor is internal like as Public class A { private string text; internal A(string submittedText); public string StrText { get; } } In this case how could I Access the constructor by using Reflection. What I have done so far Type[] pTypes = new Type[1]; pTypes[0] = typeof(object); object[] argList = new object[1]; argList[0] = "Some Text"; ConstructorInfo c = typeof(A).GetConstructor (BindingFlags.NonPublic | BindingFlags.Instance, null, pTypes, null); A foo = (A)c.Invoke(BindingFlags.NonPublic, null, argList, Application.CurrentCulture); But it shows an error. Any Suggestions

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  • Accomplishing boost::shared_from_this() in constructor via boost::shared_from_raw(this)

    - by Kyle
    Googling and poking around the boost code, it appears that it's now possible to construct a shared_ptr to this in a constructor, by inheriting from enable_shared_from_raw and calling shared_from_raw(this) Is there any documentation or examples of this? I'm finding nothing with google. Why am I not finding any useful buzz on this on google? I would have thought using shared_from_this in a constructor would be a hot/desirable item. Should I be inheriting from both enable_shared_from_raw and enable_shared_from_this, and restricting my usage of enable_shared_from_raw when I have to? If so, why? Is there a performance hit with shared_from_raw?

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  • Copy constructor with more than one parameter

    - by Ravi Gupta
    I am learning C++ and was reading copy constructor from the C++: The Complete Reference. The books says that It is permissible for a copy constructor to have additional parameters as long as they have default arguments defined for them. However, in all cases the first parameter must be a reference to the object doing the initializing. But I am confused that how we are going to pass those additional parameters? I am sure there should be some way which is not given in the book and which I am unable to figure out. Can anyone help me out? EDIT: Also is it possible to pass these extra parameters in all three cases i.e. ¦ When one object explicitly initializes another, such as in a declaration ¦ When a copy of an object is made to be passed to a function ¦ When a temporary object is generated (most commonly, as a return value)

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  • Const parameter at constructor causes stackoverflow

    - by Luca
    I've found this strange behavior with VS2005 C++ compiler. Here is the situation: I cannot publish the code, but situation is very simple. Here is initial code: it work perfectly class Foo { public: Foo(Bar &bar) { ... } } The constructor implementation stores a reference, setup some members... indeed nothing special. If I change the code in the following way: class Foo { public: Foo(const Bar &bar) { ... } } I've added a const qualifier to the only constructor routine parameter. It compiles correctly, but the compiler outputs a warning saying that the routine Foo::Foo will cause a stackoverflow (even if the execution path doesn't construct any object Foo); effectively this happens. So, why the code without the const parameter works perfectly, while the one with the const qualifier causes a stackoverflow? What can cause this strange behavior?

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  • Constructor Type Coercion in C++

    - by Robert Mason
    Take the following class: class mytype { double num; public: mytype(int a) { num = sqrt(a); } void print() { cout << num; } } Say there is a method which takes a mytype: void foo(mytype a) { a.print(); } Is it legal c++ (or is there a way to implement this) to call foo(4), which would (in theory) output 2? From what I can glean you can overload type casts from a user defined class, but not to. Can constructor do this in a standards-compliant manner (assuming, of course, the constructor is not explicit). Hopefully there is a way to in the end have this legal: int a; cin >> a; foo(a); Note: this is quite obviously not the actual issue, but just an example for posting purposes. I can't just overload the function because of inheritance and other program-specific issues.

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  • C# - Adding to an existing (generated) constructor

    - by Vaccano
    I have a constructor that is in generated code. I don't want to change the generated code (cause it would get overwritten when I regenerate), but I need to add some functionality to the constructor. Here is some example code: // Generated file public partial class MyGeneratedClass { public MyGeneratedClass() { Does some generated stuff } } The only solution I can come up with is this: // My hand made file public partial class MyGeneratedClass { public MyGeneratedClass(bool useOtherConstructor):this() { do my added functinallity } } I am fairly sure this will work, but I then have a lame unused param to my constructors and I have to go change them all. Is there a better way? If not that is fine, but I thought I would ask.

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  • Passing dependent objects to a parent constructor in Scala

    - by Nick Johnson
    Suppose I have the following class heirarchy: class A() class B(a:A) class C(b:B) class BaseClass(b:B, c:C) Now I want to implement a subclass of BaseClass, which is given an instance of A, and constructs instances of B and C, which it passes to its superclass constructor. If I could use arbitrary expressions, I'd do something like this: b = new B(a) c = new C(b) super(b, c) Because the second argument to the parent constructor depends on the value of the first argument, though, I can't see any way to do this, without using a factory function, or a gratuitous hack, such as : class IntermediateSubclass(b:B) extends BaseClass(b, new C(b)) class RealSubclass(a:A) extends IntermediateSubclass(new B(a)) Is there clean way to do this?

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  • Problem accessing base member in derived constructor

    - by LeopardSkinPillBoxHat
    Given the following classes: class Foo { struct BarBC { protected: BarBC(uint32_t aKey) : mKey(aKey) mOtherKey(0) public: const uint32_t mKey; const uint32_t mOtherKey; }; struct Bar : public BarBC { Bar(uint32_t aKey, uint32_t aOtherKey) : BarBC(aKey), mOtherKey(aOtherKey) // Compile error here }; }; I am getting a compilation error at the point indicated: error: class `Foo::Bar' does not have any field named `mOtherKey'. Can anyone explain this? I suspect it's a syntactical problem due to my Bar class being defined within the Foo class, but can't seem to find a way around it. This is simple public inheritance, so mOtherKey should be accessible from the Bar constructor. Right? Or is it something to do with the fact that mOtherKey is const and I have already initialised it to 0 in the BarBC constructor?

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  • Constructor/Destructor involving a class and a struct

    - by Bogdan Maier
    I am working on a program and need to make an array of objects, specifically I have a 31x1 array where each position is an object, (each object is basically built out of 6 ints). Here is what I have but something is wrong and i could use some help thank you. 31x1 struct header" const int days=31; struct Arr{ int days; int *M; }; typedef Arr* Array; 31x1 matrix constructor: void constr(){ int *M; M = new Expe[31]; // Expe is the class class header: class Expe { private: //0-HouseKeeping, 1-Food, 2-Transport, 3-Clothing, 4-TelNet, 5-others int *obj; } Class object constructor: Expe::Expe() { this->obj=new int[6]; } help please... because i`m pretty lost.

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  • C# COM+ component isn't getting the constructor string

    - by Kyle W
    I've created a COM+ component in C# with a strong name, COM Visible, ProgId, etc... I've then registered the assembly with regasm, and imported it into the COM+ Applications in Component Services. It runs just fine, and loads up the DLL, except that the constructor string that is passed in is always empty. The method signature is protected override void Construct(string constructString), and it is being called before the method on the actual component. In the component details in COM+ Applications, the constructor string is checked and a value is entered. Any help is appreciated.

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