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  • C++ Exam Question

    - by Carlucho
    I just took an exam where i was asked the following: Write the function body of each of the methods GenStrLen, InsertChar and StrReverse for the given code bellow. You must take into consideration the following; How strings are constructed in C++ The string must not overflow Insertion of character increases its length by 1 An empty string is indicated by StrLen = 0 class Strings { private: char str[80]; int StrLen; public: // Constructor Strings() { StrLen=0; }; // A function for returning the length of the string 'str' int GetStrLen(void) { }; // A function to inser a character 'ch' at the end of the string 'str' void InsertChar(char ch) { }; // A function to reverse the content of the string 'str' void StrReverse(void) { }; }; The answer I gave was something like this (see bellow). My one of problem is that used many extra variables and that makes me believe am not doing it the best possible way, and the other thing is that is not working.... class Strings { private: char str[80]; int StrLen; int index; // *** Had to add this *** public: Strings(){ StrLen=0; } int GetStrLen(void){ for (int i=0 ; str[i]!='\0' ; i++) index++; return index; // *** Here am getting a weird value, something like 1829584505306 *** } void InsertChar(char ch){ str[index] = ch; // *** Not sure if this is correct cuz I was not given int index *** } void StrRevrse(void){ GetStrLen(); char revStr[index+1]; for (int i=0 ; str[i]!='\0' ; i++){ for (int r=index ; r>0 ; r--) revStr[r] = str[i]; } } }; I would appreciate if anyone could explain me toughly what is the best way to have answered the question and why. Also how come my professor closes each class function like " }; " i thought that was only used for ending classes and constructors only. Thanks a lot for your help.

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  • creating an array of objects in c++

    - by tim22
    I'm trying to create an array of objects in c++. I'm creating a employee object, from my constructor in my company class here: employee obj(int tempIdNum, double tempBase, double tempSales, double tempRate); emp[tempcount]=obj; (this doesn't work?) Emp is the name of the array which is defined here, located in my company h file. Employee emp[4]; more code: Company::Company(string name, string fileName){ string str; int tempcount; int tempIdnum; double tempBase; double tempSales; double tempRate; double num; double arr[16]; this->name=name; //Commission temp; ifstream readFile; readFile.open("fileName"); int inc=0; while(tempcount<4){ for(int i=0+inc; i<4+inc; i++){ readFile>>num; arr[i-inc]=num; } tempIdnum=(int)(arr[0]); tempBase=arr[1]; tempSales=arr[2]; tempRate=arr[3]; Employee obj(int tempIdNum, double tempBase, double tempSales, double tempRate); emp[tempcount]=obj; inc+=4; tempcount++; } readFile.close(); } Here is some more from my h file #include <string> include "Commission.h" using namespace std; ifndef Company_H define Company_H class Company{ private: string name; //name of company Employee emp[4]; //array of payrool info about 4 commission employees int numEmp; //number of employees public: Company(); Company(string name, string fileName); ~Company(); string getName(); Commission getEmployee(int element); int getNumEmp(); }; endif enter code here Does not compile: 46 E:\exercise2\Company.cpp no match for 'operator=' in '((Company*)this)-Company::emp[tempcount] = obj'

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  • Derived template override return type of member function C++

    - by Ruud v A
    I am writing matrix classes. Take a look at this definition: template <typename T, unsigned int dimension_x, unsigned int dimension_y> class generic_matrix { ... generic_matrix<T, dimension_x - 1, dimension_y - 1> minor(unsigned int x, unsigned int y) const { ... } ... } template <typename T, unsigned int dimension> class generic_square_matrix : public generic_matrix<T, dimension, dimension> { ... generic_square_matrix(const generic_matrix<T, dimension, dimension>& other) { ... } ... void foo(); } The generic_square_matrix class provides additional functions like matrix multiplication. Doing this is no problem: generic_square_matrix<T, 4> m = generic_matrix<T, 4, 4>(); It is possible to assign any square matrix to M, even though the type is not generic_square_matrix, due to the constructor. This is possible because the data does not change across children, only the supported functions. This is also possible: generic_square_matrix<T, 4> m = generic_square_matrix<T, 5>().minor(1,1); Same conversion applies here. But now comes the problem: generic_square_matrix<T, 4>().minor(1,1).foo(); //problem, foo is not in generic_matrix<T, 3, 3> To solve this I would like generic_square_matrix::minor to return a generic_square_matrix instead of a generic_matrix. The only possible way to do this, I think is to use template specialisation. But since a specialisation is basically treated like a separate class, I have to redefine all functions. I cannot call the function of the non-specialised class as you would do with a derived class, so I have to copy the entire function. This is not a very nice generic-programming solution, and a lot of work. C++ almost has a solution for my problem: a virtual function of a derived class, can return a pointer or reference to a different class than the base class returns, if this class is derived from the class that the base class returns. generic_square_matrix is derived from generic_matrix, but the function does not return a pointer nor reference, so this doesn't apply here. Is there a solution to this problem (possibly involving an entirely other structure; my only requirements are that the dimensions are a template parameter and that square matrices can have additional functionality). Thanks in advance, Ruud

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  • How can I set an image for background of GUI interface?

    - by enriched
    hey everyone, im having some troubles displaying the background image for a GUI interface in java. Here is what i have at the moment, and with current stage of code it shows default(gray) background. import javax.swing.*; import java.awt.event.*; import java.util.Scanner; import java.awt.*; import java.io.File; import javax.imageio.ImageIO; import java.awt.image.BufferedImage; import java.io.IOException; ////////////////////////////////// // 3nriched Games Presents: // // MIPS The Mouse!! // ////////////////////////////////// public class mipsMouseGUI extends JFrame implements ActionListener { private static String ThePDub = ("mouse"); //the password JPasswordField pass; JPanel panel; JButton btnEnter; JLabel lblpdub; public mipsMouseGUI() { BufferedImage image = null; try { //attempts to read picture from the folder image = ImageIO.read(getClass().getResource("/mousepics/mousepic.png")); } catch (IOException e) { //catches exceptions e.printStackTrace(); } ImagePanel panel = new ImagePanel(new ImageIcon("/mousepics/neonglowOnwill.png").getImage()); setIconImage(image); //sets icon picture setTitle("Mips The Mouse Login"); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); pass = new JPasswordField(5); //sets password length to 5 pass.setEchoChar('@'); //hide characters as @ symbol pass.addActionListener(this); //adds action listener add(panel); //adds panel to frame btnEnter = new JButton("Enter"); //creates a button btnEnter.addActionListener(this);// Register the action listener. lblpdub = new JLabel(" Your Password: "); // label that says enter password panel.add(lblpdub, BorderLayout.CENTER);// adds label and inputbox panel.add(pass, BorderLayout.CENTER); // to panel and sets location panel.add(btnEnter, BorderLayout.CENTER); //adds button to panel pack(); // packs controls and setLocationRelativeTo(null); // Implicit "this" if inside JFrame constructor. setVisible(true);// makes them visible (duh) } public void actionPerformed(ActionEvent a) { Object source = a.getSource(); //char array that holds password char[] passy = pass.getPassword(); //characters array to string String p = new String(passy); //determines if user entered correct password if(p.equals(ThePDub)) { JOptionPane.showMessageDialog(null, "Welcome beta user: USERNAME."); } else JOptionPane.showMessageDialog(null, "You have enter an incorrect password. Please try again."); } public class ImagePanel extends JPanel { private BufferedImage img; public ImagePanel(String img) { this(new ImageIcon(img).getImage()); } public ImagePanel(Image img) { Dimension size = new Dimension(img.getWidth(null), img.getHeight(null)); } public void paintComponent(Graphics g) { g.drawImage(img, 0, 0, null); } } }

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  • NHibernateUnitOfWork + ASP.Net MVC

    - by Felipe
    Hi Guys, hows it going? I'm in my first time with DDD, so I'm begginer! So, let's take it's very simple :D I developed an application using asp.net mvc 2 , ddd and nhibernate. I have a domain model in a class library, my repositories in another class library, and an asp.net mvc 2 application. My Repository base class, I have a construct that I inject and dependency (my unique ISessionFactory object started in global.asax), the code is: public class Repository<T> : IRepository<T> where T : Entidade { protected ISessionFactory SessionFactory { get; private set; } protected ISession Session { get { return SessionFactory.GetCurrentSession(); } } protected Repository(ISessionFactory sessionFactory) { SessionFactory = sessionFactory; } public void Save(T entity) { Session.SaveOrUpdate(entity); } public void Delete(T entity) { Session.Delete(entity); } public T Get(long key) { return Session.Get<T>(key); } public IList<T> FindAll() { return Session.CreateCriteria(typeof(T)).SetCacheable(true).List<T>(); } } And After I have the spefic repositories, like this: public class DocumentRepository : Repository<Domain.Document>, IDocumentRepository { // constructor public DocumentRepository (ISessionFactory sessionFactory) : base(sessionFactory) { } public IList<Domain.Document> GetByType(int idType) { var result = Session.CreateQuery("from Document d where d.Type.Id = :IdType") .SetParameter("IdType", idType) .List<Domain.Document>(); return result; } } there is not control of transaction in this code, and it's working fine, but, I would like to make something to control this repositories in my controller of asp.net mvc, something simple, like this: using (var tx = /* what can I put here ? */) { try { _repositoryA.Save(objA); _repositoryB.Save(objB); _repositotyC.Delete(objC); /* ... others tasks ... */ tx.Commit(); } catch { tx.RollBack(); } } I've heared about NHibernateUnitOfWork, but i don't know :(, How Can I configure NHibernateUnitOfWork to work with my repositories ? Should I change the my simple repository ? Sugestions are welcome! So, thanks if somebody read to here! If can help me, I appretiate! PS: Sorry for my english! bye =D

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  • C++ linked list based tree structure. Sanely move nodes between lists.

    - by krunk
    The requirements: Each Node in the list must contain a reference to its previous sibling Each Node in the list must contain a reference to its next sibling Each Node may have a list of child nodes Each child Node must have a reference to its parent node Basically what we have is a tree structure of arbitrary depth and length. Something like: -root(NULL) --Node1 ----ChildNode1 ------ChildOfChild --------AnotherChild ----ChildNode2 --Node2 ----ChildNode1 ------ChildOfChild ----ChildNode2 ------ChildOfChild --Node3 ----ChildNode1 ----ChildNode2 Given any individual node, you need to be able to either traverse its siblings. the children, or up the tree to the root node. A Node ends up looking something like this: class Node { Node* previoius; Node* next; Node* child; Node* parent; } I have a container class that stores these and provides STL iterators. It performs your typical linked list accessors. So insertAfter looks like: void insertAfter(Node* after, Node* newNode) { Node* next = after->next; after->next = newNode; newNode->previous = after; next->previous = newNode; newNode->next = next; newNode->parent = after->parent; } That's the setup, now for the question. How would one move a node (and its children etc) to another list without leaving the previous list dangling? For example, if Node* myNode exists in ListOne and I want to append it to listTwo. Using pointers, listOne is left with a hole in its list since the next and previous pointers are changed. One solution is pass by value of the appended Node. So our insertAfter method would become: void insertAfter(Node* after, Node newNode); This seems like an awkward syntax. Another option is doing the copying internally, so you'd have: void insertAfter(Node* after, const Node* newNode) { Node *new_node = new Node(*newNode); Node* next = after->next; after->next = new_node; new_node->previous = after; next->previous = new_node; new_node->next = next; new_node->parent = after->parent; } Finally, you might create a moveNode method for moving and prevent raw insertion or appending of a node that already has been assigned siblings and parents. // default pointer value is 0 in constructor and a operator bool(..) // is defined for the Node bool isInList(const Node* node) const { return (node->previous || node->next || node->parent); } // then in insertAfter and friends if(isInList(newNode) // throw some error and bail I thought I'd toss this out there and see what folks came up with.

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  • C++ segmentation error when first parameter is null in comparison operator overload

    - by user1774515
    I am writing a class called Word, that handles a c string and overloads the <, , <=, = operators. word.h: friend bool operator<(const Word &a, const Word &b); word.cc: bool operator<(const Word &a, const Word &b) { if(a == NULL && b == NULL) return false; if(a == NULL) return true; if(b == NULL) return false; return a.wd < b.wd; //wd is a valid c string } main: char* temp = NULL; //EDIT: i was mistaken, temp is a char pointer Word a("blah"); //a.wd = [b,l,a,h] cout << (temp<a); i get a segmentation error before the first line of the operator< method after the last line in the main. I can correct the problem by writing cout << (a>temp); where the operator> is similarly defined and i get no errors. but my assignment requires (temp < a) to work so this is where i ask for help. EDIT: i made a mistake the first time and i said temp was of type Word, but it is actually of type char*. so i assume that the compiler converts temp to a Word using one of my constructors. i dont know which one it would use and why this would work since the first parameter is not Word. here is the constructor i think is being used to make the Word using temp: Word::Word(char* c, char* delimeters=NULL) { char *temporary = "\0"; if(c == NULL) c = temporary; check(stoppers!=NULL, "(Word(char*,char*))NULL pointer"); //exits the program if the expression is false if(strlen(c) == 0) size = DEFAULT_SIZE; //10 else size = strlen(c) + 1 + DEFAULT_SIZE; wd = new char[size]; check(wd!=NULL, "Word(char*,char*))heap overflow"); delimiters = new char[strlen(stoppers) + 1]; //EDIT: changed to [] check(delimiters!=NULL,"Word(char*,char*))heap overflow"); strcpy(wd,c); strcpy(delimiters,stoppers); count = strlen(wd); } wd is of type char* thanks for looking at this big question and trying to help. let me know if you need more code to look at

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  • error: expected `;' before '{' token - What is the cause?

    - by melee
    Here is my implementation file: using namespace std; #include <iostream> #include <iomanip> #include <string> #include <stack> //line 5 #include "proj05.canvas.h" //----------------Constructor----------------// Canvas::Canvas() //line 10 { Title = ""; Nrow = 0; Ncol = 0; image[][100]; // line 15 position.r = 0; position.c = 0; } //-------------------Paint------------------// line 20 void Canvas::Paint(int R, int C, char Color) { cout << "Paint to be implemented" << endl; } The errors I'm getting are these: proj05.canvas.cpp: In function 'std::istream& operator>>(std::istream&, Canvas&)': proj05.canvas.cpp:11: error: expected `;' before '{' token proj05.canvas.cpp:22: error: a function-definition is not allowed here before '{' token proj05.canvas.cpp:24: error: expected `}' at end of input proj05.canvas.cpp:24: error: expected `}' at end of input These seem like simple syntax errors, but I am not sure what's wrong. Could someone decode these for me? I'd really appreciate it, thanks for your time! EDIT Here is the definition of Canvas in my .h file: #ifndef CANVAS_H #define CANVAS_H #include <iostream> #include <iomanip> #include <string> #include <stack> class Canvas { public: Canvas(); void Paint(int R, int C, char Color); const int Nrow; const int Ncol; string Title; int image[][100]; stack<int> path; struct PixelCoordinates { unsigned int r; unsigned int c; } position; }; #endif

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  • assignment not working in a dll exported C++ class

    - by Jim Jones
    Using VS 2008 Have a C++ class in which I'm calling functions from a 3rd party dll. The definition in the header file is as follows: namespace OITImageExport { class ImageExport { private: SCCERR seResult; /* Error code returned. */ VTHDOC hDoc; /* Input doc handle returned by DAOpenDocument(). */ VTHEXPORT hExport; /* Handle to the export returned by EXOpenExport(). */ VTDWORD dwFIFlags; /* Used in setting the SCCOPT_FIFLAGS option. */ VTCHAR szError[256]; /* Error string buffer. */ VTDWORD dwOutputId; /* Output Format. */ VTDWORD dwSpecType; public: ImageExport(const char* outputId, const char* specType); void ProcessDocument(const char* inputPath, const char* outputPath); ~ImageExport(); }; } In the constructor I initialize two of the class fields having values which come from enumerations in the 3rd party dll: ImageExport::ImageExport(const char* outputId, const char* specType) { if(outputId == "jpeg") { dwOutputId = FI_JPEGFIF; } if(specType == "ansi") { dwSpecType = IOTYPE_ANSIPATH; } seResult = DAInit(); if (seResult != SCCERR_OK) { DAGetErrorString(seResult, szError, sizeof(szError)); fprintf(stderr, "DAInit() failed: %s (0x%04X)\n", szError, seResult); exit(seResult); } } When I use this class inside of a console app, with a main method in another file (all in the same namespace), instantiating the class object and calling the methods, it works like a champ. So, now that I know the basic code works, I open a dll project using the class header and code file. Course I have to add the dll macro, namely: #ifdef IMAGEDLL_EXPORTS #define DLL __declspec(dllexport) #else #define DLL __declspec(dllimport) #endif and changed the class definition to "class DLL ImageExport". Compiled nicely to a dll and .lib file (No errors, No warnings). Now to test this dll I open another console project using the same main method as before and linking to the (dll) lib file. Had problems, which when tracked down were the result of the two fields not being set; both had values of 0. Went back to the first console app and printed out the values: dwOutputId was 1535 (#define FI_JPEGFIF 1535) and dwSpecType was 2 (#define IOTYPE_ANSIPATH 2). Now if I was assigning these values outside of the class, I can see how the visibility could be different, but why is the assignment in the dll not working? Is it something about having a class in the dll?

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  • How to control manager class in Blackberry

    - by Keng
    Dear All, I have a problem when creating a UI on Blackberry. First, i try to create a ChatLayoutManager class extended from Manager class. My layout has three component: topfield, mainfield and bottom field. public class ChatLayoutManager extends Manager { private Field bottomField; private Field mainField; private Field titleField; public ChatLayoutManager(long style) { super(style); } protected void sublayout(int width, int height) { setExtent(width, height); int y = 0; if (bottomField != null) { layoutChild(bottomField, width, height); // This goes at the bottom of the screen setPositionChild(bottomField, 0, height-bottomField.getHeight()); height -= bottomField.getHeight(); } if (titleField != null) { layoutChild(titleField, width, height); // This goes at the top of the screen setPositionChild(titleField, 0, 0); height -= titleField.getHeight(); y += titleField.getHeight(); } if (mainField != null) { layoutChild(mainField, width, height); // This goes just below the title field (if any) setPositionChild(mainField, 0, y); } } public void setMainField(Field f) { mainField = f; add(f); } public void setBottomField(Field f) { bottomField = f; add(f); } public void setTitleField(Field f) { titleField = f; add(f); } Then i create another field (ChatField) extended from manager to add to mainfield in the ChatLayoutManager class which i have created above. public class ChatField extends Manager{ private Field _contentField[]; protected ChatField(){ super(Manager.HORIZONTAL_SCROLL | Manager.VERTICAL_SCROLL); } // TODO Auto-generated constructor stub} protected synchronized void sublayout(int width, int height) { // TODO Auto-generated method stub setExtent(width, height); int x = 0; int y = 0; if(_contentField.length > 0){ for(int i = 0 ;i<_contentField.length; i++){ //if(getManager() == this){ this.layoutChild(_contentField[i], _contentField[i].getWidth(), _contentField[i].getHeight()); this.setPositionChild(_contentField[i], x, y); if(_contentField[i++]!= null){ if ((_contentField[i].getWidth() + _contentField[i].getWidth()) >= width){ x = 0; y += _contentField[i].getHeight(); } else{ x += _contentField[i].getWidth(); } } //} } } } public void setContentField(Field field[]){ _contentField = field; } } And now, when i create some fields(such as TextField, BitmapField ...) added to ChatField, the program has an error "Field is not a child of this manager". The reason is when the framework invokes the sublayout function of the ChatField class , when sublayout starts calling layoutChild function the manager of field is not ChatField but ChatlayoutManager. I've experience hard time trying to resolve this problem, still I have no solution. Anybody can give me some suggestions? I really appreciate.

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  • C++ exam question on string class implementation

    - by Carlucho
    I just took an exam where i was asked the following: Write the function body of each of the methods GenStrLen, InsertChar and StrReverse for the given code bellow. You must take into consideration the following; How strings are constructed in C++ The string must not overflow Insertion of character increases its length by 1 An empty string is indicated by StrLen = 0 class Strings { private: char str[80]; int StrLen; public: // Constructor Strings() { StrLen=0; }; // A function for returning the length of the string 'str' int GetStrLen(void) { }; // A function to inser a character 'ch' at the end of the string 'str' void InsertChar(char ch) { }; // A function to reverse the content of the string 'str' void StrReverse(void) { }; }; The answer I gave was something like this (see bellow). My one of problem is that used many extra variables and that makes me believe am not doing it the best possible way, and the other thing is that is not working.... class Strings { private: char str[80]; int StrLen; int index; // *** Had to add this *** public: Strings(){ StrLen=0; } int GetStrLen(void){ for (int i=0 ; str[i]!='\0' ; i++) index++; return index; // *** Here am getting a weird value, something like 1829584505306 *** } void InsertChar(char ch){ str[index] = ch; // *** Not sure if this is correct cuz I was not given int index *** } void StrRevrse(void){ GetStrLen(); char revStr[index+1]; for (int i=0 ; str[i]!='\0' ; i++){ for (int r=index ; r>0 ; r--) revStr[r] = str[i]; } } }; I would appreciate if anyone could explain me toughly what is the best way to have answered the question and why. Also how come my professor closes each class function like " }; " i thought that was only used for ending classes and constructors only. Thanks a lot for your help.

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  • Dynamic allocating of const member structures

    - by Willy
    I've got class which is using plain-only-data struct with const variables and I'm not sure, if I'm allocating these structures in a proper way. It looks more or less like: #include <cstdlib> #include <iostream> using std::cout; using std::endl; struct some_const_struct { const int arg1; const int arg2; }; class which_is_using_above_struct { public: some_const_struct* m_member; const some_const_struct* const m_const_member; public: const some_const_struct& get_member() const { return *m_member; } const some_const_struct& get_const_member() const { return *m_const_member; } void set_member(const int a, const int b) { if(m_member != NULL) { delete m_member; m_member = NULL; } m_member = new some_const_struct((some_const_struct){a, b}); } explicit which_is_using_above_struct(const int a, const int b) : m_const_member(new some_const_struct((const some_const_struct){a, b})) { m_member = NULL; } ~which_is_using_above_struct() { if(m_member != NULL) { delete m_member; } if(m_const_member != NULL) { delete m_const_member; } } }; int main() { which_is_using_above_struct c(1, 2); c.set_member(3, 4); cout << "m_member.arg1 = " << c.get_member().arg1 << endl; cout << "m_member.arg2 = " << c.get_member().arg2 << endl; cout << "m_const_member.arg1 = " << c.get_const_member().arg1 << endl; cout << "m_const_member.arg2 = " << c.get_const_member().arg2 << endl; return 0; } I'm just not quite sure if the statement: m_member = new some_const_struct((some_const_struct){a, b}); doesn't produce unnessesary use of some_const_struct's copy constructor, ergo allocating that struct twice. What do you think? And is it reasonable to make that struct's members const? (they're not supposed to change in their lifetime at all)

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  • Better way to write an object generator for an RAII template class?

    - by Dan
    I would like to write an object generator for a templated RAII class -- basically a function template to construct an object using type deduction of parameters so the types don't have to be specified explicitly. The problem I foresee is that the helper function that takes care of type deduction for me is going to return the object by value, which will result in a premature call to the RAII destructor when the copy is made. Perhaps C++0x move semantics could help but that's not an option for me. Anyone seen this problem before and have a good solution? This is what I have: template<typename T, typename U, typename V> class FooAdder { private: typedef OtherThing<T, U, V> Thing; Thing &thing_; int a_; // many other members public: FooAdder(Thing &thing, int a); ~FooAdder(); void foo(T t, U u); void bar(V v); }; The gist is that OtherThing has a horrible interface, and FooAdder is supposed to make it easier to use. The intended use is roughly like this: FooAdder(myThing, 2) .foo(3, 4) .foo(5, 6) .bar(7) .foo(8, 9); The FooAdder constructor initializes some internal data structures. The foo and bar methods populate those data structures. The ~FooAdder dtor wraps things up and calls a method on thing_, taking care of all the nastiness. That would work fine if FooAdder wasn't a template. But since it is, I would need to put the types in, more like this: FooAdder<Abc, Def, Ghi>(myThing, 2) ... That's annoying, because the types can be inferred based on myThing. So I would prefer to create a templated object generator, similar to std::make_pair, that will do the type deduction for me. Something like this: template<typename T, typename U, typename V> FooAdder<T, U, V> AddFoo(Thing &thing, int a) { return FooAdder<T, U, V>(thing, a); } That seems problematic: because it returns by value, the stack temporary object will be destructed, which will cause the RAII dtor to run prematurely. One thought I had was to give FooAdder a copy ctor with move semantics, kinda like std::auto_ptr. But I would like to do this without dynamic memory allocation, so I thought the copy ctor could set a flag within FooAdder indicating the dtor shouldn't do the wrap-up. Like this: FooAdder(FooAdder &rhs) // Note: rhs is not const : thing_(rhs.thing_) , a_(rhs.a_) , // etc... lots of other members, annoying. , moved(false) { rhs.moved = true; } ~FooAdder() { if (!moved) { // do whatever it would have done } } Seems clunky. Anyone got a better way?

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  • C++ abstract class template + type-specific subclass = trouble with linker

    - by user333279
    Hi there, The project in question is about different endpoints communicating with each other. An endpoint sends events (beyond the scope of the current problem) and can process incoming events. Each event is represented in a generic object as follows: #pragma interface ... // some includes template<typename T> class Event { public: Event(int senderId, Type type, T payload); // Type is an enum Event(int senderId, Type type, int priority, T payload); virtual ~Event(); virtual int getSenderId(); virtual int getPriority(); virtual T getPayload(); void setPriority(const int priority); protected: const int senderId; const Type type; const T payload; int priority; }; It has its implementing class with #pragma implementation tag. An endpoint is defined as follows: #pragma interface #include "Event.h" template<typename T> class AbstractEndPoint { public: AbstractEndPoint(int id); virtual ~AbstractEndPoint(); virtual int getId(); virtual void processEvent(Event<T> event) = 0; protected: const int id; }; It has its implementing class too, but only the constructor, destructor and getId() are defined. The idea is to create concrete endpoints for each different payload type. Therefore I have different payload objects and specific event classes for each type, e.g. Event<TelegramFormatA>, Event<TelegramFormatB> and ConcreteEndPoint for TelegramFormatA, ConcreteEndPoint for TelegramFormatB respectively. The latter classes are defined as class ConcreteEndPoint : AbstractEndPoint<TelegramFormatA> { ... } I'm using g++ 4.4.3 and ld 2.19. Everything compiles nicely, but the linker complaints about undefined references to type-specific event classes, like Event<TelegramFormatA>::Event(....) . I tried explicit instantiation using template class AbstractEndPoint<TelegramFormatA>; but couldn't get past the aforementioned linker errors. Any ideas would be appreciated.

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  • When does logic belong in the Business Object/Entity, and when does it belong in a Service?

    - by Casey
    In trying to understand Domain Driven Design I keep returning to a question that I can't seem to definitively answer. How do you determine what logic belongs to a Domain entity, and what logic belongs to a Domain Service? Example: We have an Order class for an online store. This class is an entity and an aggregate root (it contains OrderItems). Public Class Order:IOrder { Private List<IOrderItem> OrderItems Public Order(List<IOrderItem>) { OrderItems = List<IOrderItem> } Public Decimal CalculateTotalItemWeight() //This logic seems to belong in the entity. { Decimal TotalWeight = 0 foreach(IOrderItem OrderItem in OrderItems) { TotalWeight += OrderItem.Weight } return TotalWeight } } I think most people would agree that CalculateTotalItemWeight belongs on the entity. However, at some point we have to ship this order to the customer. To accomplish this we need to do two things: 1) Determine the postage rate necessary to ship this order. 2) Print a shipping label after determining the postage rate. Both of these actions will require dependencies that are outside the Order entity, such as an external webservice to retrieve postage rates. How should we accomplish these two things? I see a few options: 1) Code the logic directly in the domain entity, like CalculateTotalItemWeight. We then call: Order.GetPostageRate Order.PrintLabel 2) Put the logic in a service that accepts IOrder. We then call: PostageService.GetPostageRate(Order) PrintService.PrintLabel(Order) 3) Create a class for each action that operates on an Order, and pass an instance of that class to the Order through Constructor Injection (this is a variation of option 1 but allows reuse of the RateRetriever and LabelPrinter classes): Public Class Order:IOrder { Private List<IOrderItem> OrderItems Private RateRetriever _Retriever Private LabelPrinter _Printer Public Order(List<IOrderItem>, RateRetriever Retriever, LabelPrinter Printer) { OrderItems = List<IOrderItem> _Retriever = Retriever _Printer = Printer } Public Decimal GetPostageRate { _Retriever.GetPostageRate(this) } Public void PrintLabel { _Printer.PrintLabel(this) } } Which one of these methods do you choose for this logic, if any? What is the reasoning behind your choice? Most importantly, is there a set of guidelines that led you to your choice?

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  • Why am I getting ClassNotFoundExpection when I have properly imported said class and am looking at it in its directory?

    - by Strider
    This is my Javac compiling statement: javac -cp "C:\java\code\j3D\j3dcore.jar;C:\java\code\j3D\j3dutils.jar;C:\java\code\j3D\vecmath.jar" Simple.java compiles with no problems. The three jar files (j3dcore, j3dutils, and vecmath) are the essential jar's for my program (or at least I am led to believe according to this official tutorial on J3D For the record I ripped this code almost line from line from this pdf file. jar files are correctly located in referenced locations When I run my Simple program, (java Simple) I am greeted with Exception in thread "main" java.lang.NoClassDefFoundError: javax/media/j3d/Cavas3d Caused by: java.lang.ClassNotFoundExpection: javax.media.j3d.Canvas3D Currently I am staring directly at this Canvas3D.class that is located within j3dcore.jar\javax\media\j3d\ wtfisthis.jpg Here is the source code: //First java3D Program import java.applet.Applet; import java.awt.BorderLayout; import java.awt.Frame; import java.awt.event.*; import com.sun.j3d.utils.applet.MainFrame; import com.sun.j3d.utils.universe.*; import com.sun.j3d.utils.geometry.ColorCube; import javax.media.j3d.*; import javax.vecmath.*; import java.awt.GraphicsConfiguration; public class Simple extends Applet { public Simple() { setLayout(new BorderLayout()); GraphicsConfiguration config = SimpleUniverse.getPreferredConfiguration(); Canvas3D canvas3D = new Canvas3D(config); add("Center", canvas3D); BranchGroup scene = createSceneGraph(); scene.compile(); // SimpleUniverse is a Convenience Utility class SimpleUniverse simpleU = new SimpleUniverse(canvas3D); // This moves the ViewPlatform back a bit so the // objects in the scene can be viewed. simpleU.getViewingPlatform().setNominalViewingTransform(); simpleU.addBranchGraph(scene); } // end of HelloJava3Da (constructor) public BranchGroup createSceneGraph() { // Create the root of the branch graph BranchGroup objRoot = new BranchGroup(); // Create a simple shape leaf node, add it to the scene graph. // ColorCube is a Convenience Utility class objRoot.addChild(new ColorCube(0.4)); return objRoot; } public static void main(String args[]){ Simple world = new Simple(); } }` Did I import correctly? Did I incorrectly reference my jar files in my Javac statement? If I clearly see Canvas3D within its correct directory why cant java find it? The first folder in both j3dcore.jar and vecmath.jar is "javax". Is the compiler getting confused? If the compiler is getting confused how do I specify where to find that exact class when referencing it within my source code?

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  • Randomised objects are assigning themselves to more than one array location

    - by Thaddeus Aid
    this.size = 9; this.populationSize = 10; Random rand = new Random(); Integer[][] easy1 = new Integer[size][size]; easy1 = this.initializeEasy1(easy1); this.sudokuArray = new Sudoku[this.populationSize]; for (int i = 0; i < this.sudokuArray.length; i++){ long seed = rand.nextLong(); System.out.println("" + seed); this.sudokuArray[i] = new Sudoku(easy1, this.size, seed); } I am building an evolutionary sudoku solver and I am having a problem where the last Sudoku object is overwriting all the other objects in the array. Where in the code did I mess up? /edit here is the constructor of the class public Sudoku(Integer[][] givensGrid, int s, long seed){ this.size = s; this.givens = givensGrid; this.grid = this.givens.clone(); Random rand = new Random(seed); System.out.println("Random " + rand.nextInt()); // step though each row of the grid for (int i = 0; i < size; i++){ ArrayList<Integer> numbers = new ArrayList<Integer>(); numbers = this.makeNumbers(numbers); // step through each column to find the givens and remove from numbers for (int j = 0; j < size; j++){ if (this.grid[i][j] != 0){ numbers.remove(this.grid[i][j]); } } // go back through the row and assign the numbers randomly for (int j = 0; j < size; j++){ if (this.grid[i][j] == 0){ int r = rand.nextInt(numbers.size()); this.grid[i][j] = numbers.get(r); numbers.remove(r); } } } System.out.println("============="); System.out.println(this.toString()); }

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  • Silverlight: Binding to a LayoutRoot value from within a DataTemplate

    - by Rosarch
    I have a DataTemplate for a ListBox, where I have several controls that bind to an item. I would also like to bind to a value on LayoutRoot.DataContext. I'm unsure of how to do this. <!--LayoutRoot is the root grid where all page content is placed--> <StackPanel x:Name="LayoutRoot" Background="Transparent"> <ListBox ItemsSource="{Binding Items}"> <ListBox.ItemTemplate> <DataTemplate> <StackPanel> <TextBlock Text="{Binding}" /> <TextBlock Text="{Binding ElementName=LayoutRoot, Path=DataContext.Foo}" /> </StackPanel> </DataTemplate> </ListBox.ItemTemplate> </ListBox> </StackPanel> public partial class MainPage : PhoneApplicationPage { public string Foo { get { return "the moon"; } } private int startIndex = 1; private IList<string> _data = new List<string>() { "foo", "bar", "baz" }; public IList<string> Items { get { return _data; } } // Constructor public MainPage() { InitializeComponent(); LayoutRoot.DataContext = this; } } This doesn't work; only the _data items are displayed. The following binding errors appear in the Debug output: System.Windows.Data Error: BindingExpression path error: 'Foo' property not found on 'foo' 'System.String' (HashCode=1502598398). BindingExpression: Path='DataContext.Foo' DataItem='System.Windows.Controls.Border' (HashCode=78299055); target element is 'System.Windows.Controls.TextBlock' (Name=''); target property is 'Text' (type 'System.String').. System.Windows.Data Error: BindingExpression path error: 'Foo' property not found on 'bar' 'System.String' (HashCode=696029481). BindingExpression: Path='DataContext.Foo' DataItem='System.Windows.Controls.Border' (HashCode=78298703); target element is 'System.Windows.Controls.TextBlock' (Name=''); target property is 'Text' (type 'System.String').. System.Windows.Data Error: BindingExpression path error: 'Foo' property not found on 'baz' 'System.String' (HashCode=696029489). BindingExpression: Path='DataContext.Foo' DataItem='System.Windows.Controls.Border' (HashCode=78298694); target element is 'System.Windows.Controls.TextBlock' (Name=''); target property is 'Text' (type 'System.String').. Do I have a syntax error somewhere? Update I'm aiming for something that looks like this: foo the moon bar the moon baz the moon Instead, all I'm getting is: foo bar baz

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  • new operator overwriting an existing object

    - by dvpdiner2
    I have a custom FastStack class, implemented as a fixed size array and an index into that array. In my copy constructor, I allocate the array and then assign each object from the copy's array into the new array. There's some refcounting in the objects on the stack, hence assignment is used rather than a simple copy. The problem is that when allocating the array, it sometimes overwrites part of the other stack's array. As can be expected, this leads to eventual segmentation faults when that data is dereferenced. class FastStack { private: int m_size, m_ptr; ObjectRef* m_stack; public: FastStack(int size) : m_size(size), m_ptr(-1) { m_stack = new ObjectRef[m_size]; } FastStack(const FastStack& copy) : m_size(copy.m_size), m_ptr(copy.m_ptr) { long a = (long)copy.m_stack[0]; m_stack = new ObjectRef[m_size]; if ((long)copy.m_stack[0] != a) fprintf(stderr, "\nWe have a serious problem!\n\n"); for (int i = 0; i <= m_ptr; i++) m_stack[i] = copy.m_stack[i]; } ~FastStack() { delete[] m_stack; } }; class ObjectRef { private: DataObj* m_obj; public: ObjectRef() : m_obj(0) { } ObjectRef(DataObj* obj) : m_obj(obj) { if (m_obj) m_obj->addRef(); } ObjectRef(const ObjectRef& obj) : m_obj(obj.m_obj) { if (m_obj) m_obj->addRef(); } ~ObjectRef() { if (m_obj) m_obj->delRef(); } ObjectRef& operator=(DataObj* obj) { if (obj) obj->addRef(); if (m_obj) m_obj->delRef(); m_obj = obj; return *this; } ObjectRef& operator=(const ObjectRef& obj) { if (obj.m_obj) obj.m_obj->addRef(); if (m_obj) m_obj->delRef(); m_obj = obj.m_obj; return *this; } }; I see that "We have a serious problem!" line shortly before a segfault, and stepping through it with gdb I can see that one of the ObjectRefs created by new has the same address as the other stack's array. My first instinct is to say that new should never be allocating memory that is already in use, but that clearly seems to be the case here and I am at a complete loss as to what can be done. Added: At the time that I see this happen, m_size = 2 and m_ptr = 0.

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  • C#: Object having two constructors: how to limit which properties are set together?

    - by Dr. Zim
    Say you have a Price object that accepts either an (int quantity, decimal price) or a string containing "4/$3.99". Is there a way to limit which properties can be set together? Feel free to correct me in my logic below. The Test: A and B are equal to each other, but the C example should not be allowed. Thus the question How to enforce that all three parameters are not invoked as in the C example? AdPrice A = new AdPrice { priceText = "4/$3.99"}; // Valid AdPrice B = new AdPrice { qty = 4, price = 3.99m}; // Valid AdPrice C = new AdPrice { qty = 4, priceText = "2/$1.99", price = 3.99m};// Not The class: public class AdPrice { private int _qty; private decimal _price; private string _priceText; The constructors: public AdPrice () : this( qty: 0, price: 0.0m) {} // Default Constructor public AdPrice (int qty = 0, decimal price = 0.0m) { // Numbers only this.qty = qty; this.price = price; } public AdPrice (string priceText = "0/$0.00") { // String only this.priceText = priceText; } The Methods: private void SetPriceValues() { var matches = Regex.Match(_priceText, @"^\s?((?<qty>\d+)\s?/)?\s?[$]?\s?(?<price>[0-9]?\.?[0-9]?[0-9]?)"); if( matches.Success) { if (!Decimal.TryParse(matches.Groups["price"].Value, out this._price)) this._price = 0.0m; if (!Int32.TryParse(matches.Groups["qty"].Value, out this._qty)) this._qty = (this._price > 0 ? 1 : 0); else if (this._price > 0 && this._qty == 0) this._qty = 1; } } private void SetPriceString() { this._priceText = (this._qty > 1 ? this._qty.ToString() + '/' : "") + String.Format("{0:C}",this.price); } The Accessors: public int qty { get { return this._qty; } set { this._qty = value; this.SetPriceString(); } } public decimal price { get { return this._price; } set { this._price = value; this.SetPriceString(); } } public string priceText { get { return this._priceText; } set { this._priceText = value; this.SetPriceValues(); } } }

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  • Convert Object Hierachey to Object Array

    - by Killercam
    All, I want to create an object array foo[], where the constructor for Foo is public Foo(string name, string discription){} I have a database object which has a structure (not incuding stored procedures, functions or views for simplicity) like public class Database { public string name { get; set; } public string filename { get; set; } public List<Table> tables { get; set; } public Database(string name, string filename) { this.name = name; this.filename = filename; } } protected internal class Table { public string name { get; set; } public List<Column> columns { get; set;} public Table(string name, List<Column> columns) { this.name = name; this.columns = columns; } } protected internal class Column { public string name { get; set; } public string type { get; set; } public Column(string name, string type, int maxLength, bool isNullable) { this.name = name; this.type = type; } } I would like to know the quickest way to add Column and Table information to the Foo[] object array? Clearly I can do List<Foo> fooList = new List<Foo>(); foreach (Table t in database.tables) { fooList.Add(new Foo(t.Name, "Some Description")); foreach (Column c in t.columns) fooList.Add(new Foo(c.Name, "Some Description")); } Foo[] fooArr = fooList.ToArray<Foo>(); But is there a quicker way? Clearly LINQ is likely to be slower for a query that does a simalar operation, but I care allot about speed here so any advice would be appreciated. Perhaps the use of a HashSet would be the way to go as there will not be duplicate entries... Thanks for your time.

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  • Instantiating custom PropertySourcesPlaceholderConfigurer from spring context

    - by mmona
    I want to define a custom PropertySourcesPlaceholderConfigurer in spring context xml. I want to use there multiple PropertySources, so that I can load part of the configuration from several property files and provide other part dynamically by my custom PropertySource implementation. The advantage is that it should be then easy to adjust the order of loading these property sources just by making modifications to the xml spring configuration. And here I run into a problem: how to define an arbitrary list of PropertySources and inject it into PropertySourcesPlaceholderConfigurer, so that it uses the sources defined by me? Seems to be a basic thing that should be provided by spring, but since yesterday I cannot find a way to do it. Using namespace would enable me to load several property files, but I also need to define the id of the PropertySourcesPlaceholderConfigurer (as other projects refer to it), and also I want to use my custom implementation. That is why I am defining the bean explicitly and not using the namespace. The most intuitive way would be to inject a list of PropertySources into PropertySourcesPlaceholderConfigurer like this: <bean id="applicationPropertyPlaceholderConfigurer" class="org.springframework.context.support.PropertySourcesPlaceholderConfigurer"> <property name="ignoreUnresolvablePlaceholders" value="true" /> <property name="ignoreResourceNotFound" value="true" /> <property name="order" value="0"/> <property name="propertySources"> <list> <!-- my PropertySource objects --> </list> </property> </bean> but unfortunately propertySources is of type PropertySources and does not accept a list. The PropertySources interface has one and only implementor which is MutablePropertySources, which indeed stores list of PropertySource objects, but has no constructor nor setter through which I can inject this list. It only has add*(PropertySource) methods. The only workaround I see now is to implement my own PropertySources class, extending MutablePropertySources, which would accept list of PropertySource objects on creation and manually add it via using add*(PropertySource) method. But why so much workaround would be needed to provide something that I thought was supposed to be the main reason of introducing the PropertySources (having flexible configuration manageable from spring configuration level). Please clarify what am I getting wrong :)

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  • C# ATM Bank coding help needed please

    - by user1735692
    if anyone can help with with I would be grateful. I am trying to make a program in c# that acts like an ATM with withdrawing, depositing money, displayed in Program.cs that is connected to Account.cs linked class programs. At the moment it works if I manually input the data and tell it what to display, but I what to do is - Allow users to enter amounts to deposit and withdraw using overloaded implementations of the methods makeDeposit and makeWithdrawal. I have tried many things, and can not get it to work, if anyone can help, I would be grateful if anyone can, thanks again Program.cs using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Tut9 { class Program { static void Main(string[] args) { Account myAcc = new Account(); myAcc.makeDeposit(10000); myAcc.showBalance(); Console.WriteLine("Attempting to withdraw £" + 90); myAcc.makeWithdrawal(90); myAcc.showBalance(); myAcc.giveOverdraft(50); myAcc.showBalance(); Account student = new Account(30, -100); student.giveOverdraft(-500); } } } Account.cs using System; using System.Collections.Generic; using System.Linq; using System.Text; namespace Tut9 { class Account { ////Need to know the balance & ovedraft private int balance; private int overdraft; ////Constructor public Account() { balance = 0; overdraft = 0; } public Account(int initial) { balance = initial; } public Account(int intial, int over) { balance = intial; overdraft = over; } public void giveOverdraft(int amount) { overdraft = amount; } ////Method to display the balance & overdraft public void showBalance() { Console.WriteLine("The balance is now £" + balance); if (overdraft != 0) { Console.WriteLine("You have an overdraft of £" + overdraft); } } ////Method to make a withdrawl public void makeWithdrawal(int y) { balance = balance - y; Console.WriteLine("Withdrew £" + y); } ////Method to make deposit public void makeDeposit(int x) { balance = balance + x; Console.WriteLine("Desposited £" + x); } } }

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  • Starting jetty with spring xml as a background process/thread

    - by compass
    My goal is to set up a jetty test server and inject a custom servlet to test some REST classes in my project. I was able to launch the server with spring xml and run tests against that server. The issue I'm having is sometimes after the server started, the process stopped at the point before running the tests. It seems jetty didn't go to background. It works every time on my computer. But when I deployed to my CI server, it doesn't work. It also doesn't work when I'm on VPN. (Strange.) The server should be completed initialized as when the tests stuck, I was able to access the server using a browser. Here is my spring context xml: .... <bean id="servletHolder" class="org.eclipse.jetty.servlet.ServletHolder"> <constructor-arg ref="courseApiServlet"/> </bean> <bean id="servletHandler" class="org.eclipse.jetty.servlet.ServletContextHandler"/> <!-- Adding the servlet holders to the handlers --> <bean id="servletHandlerSetter" class="org.springframework.beans.factory.config.MethodInvokingFactoryBean"> <property name="targetObject" ref="servletHandler"/> <property name="targetMethod" value="addServlet"/> <property name="arguments"> <list> <ref bean="servletHolder"/> <value>/*</value> </list> </property> </bean> <bean id="httpTestServer" class="org.eclipse.jetty.server.Server" init-method="start" destroy-method="stop" depends-on="servletHandlerSetter"> <property name="connectors"> <list> <bean class="org.eclipse.jetty.server.nio.SelectChannelConnector"> <property name="port" value="#{settings['webservice.server.port']}" /> </bean> </list> </property> <property name="handler"> <ref bean="servletHandler" /> </property> </bean> Running latest Jetty 8.1.8 server and Spring 3.1.3. Any idea?

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  • How do I pass a javascript parameter to an asp.net MVCmodel from within a View?

    - by Josh
    Hi everyone! I am having an issue trying to access a list property on a model from within a javascript. My basic situation is this: I have an ArticleController and an ArticleViewModel. An Article has a number of properties, one of which is Text, which is just a string that contains the contents of the article. The ArticleViewModel contains a Pages property, which is just a List of Strings. When the ArticleViewModel constructor is called, I populate the Pages list by dividing up the article text based on some delimeters. I have a View which inherits the ArticleViewModel type. What I want to do is only display one page at a time, and then when the user clicks a page number (from a list at the bottom of the article), I want to use javascript to load that page into the #dynamicContent div. The problem: I can't seem to pass a parameter to the Model.Pages property from within javascript... Is this possible? I get an error stating, "Expression Expected" when I try what I have below. I don't want to have to worry about AJAX calls or anything like that since I already have the entire article... I just need a way to access each individual page from within the javascript function. Alternatively, if there is a better solution for "paginating" an article so that I can load each articlePage without having to refresh the entire html page, I would certainly be open to that as well. Any help would be much appreciated!! Thanks for your time! ArticleView Code: Script at the top of the view: function loadPage(pageNumber) { try { alert(pageNumber); $('#dynamicContent').html('<%=Model.Pages(' + pageNumber + ') %>'); } catch (e) { alert('in here'); alert(e.description); } } HTML for view: [...] <div id="articleBody"> <div id="dynamicContent"> <%=Model.Pages(0)%> </div> </div> [...] Page Links at bottom of page: [...] <div> <ul style="display:block"> <li style="display:inline"> <a href="#articleTitle" onclick="loadPage(0)"> 1 </a> </li> <li style="display:inline"> <a href="#articleTitle" onclick="loadPage(1)"> 2 </a> </li> </ul> </div>

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