C++ :: Vector Of Pointers - Push Back Objects / Constant Parameters
Apr 11, 2014
I have a class called Question:
#include <string>
#include <vector>
using namespace std;
class Question {
string title;
vector<Thing*> posAns;
vector<Thing*> negAns;
[Code] ....
error: no instance of overloaded function 'std::vector::push_back()' matches the arguments list
argument types are (const Thing *)
object type is: std:: vector<Thing *, std::allocator<Thing *>>
So it cannot be constant, what if I just leave it non-constant? Will it be safe?
How to output vector contents using the push_back function. My program reads in values just fine, but it does not output anything and I've been stuck on why.
here is my code:
#include <iostream> #include <array> #include <vector> using namespace std; int duplicate( vector < int > &vector1, const int value, const int counter)
Code: class moClassValueContainer { public: moClassValueContainer(); moClassValueContainer(string,int); [Code] ....
In my main.cpp, I have blow loop
Code: for (xml_node tnode = it->first_child(); tnode ; tnode = tnode.next_sibling()) { Container tmpContainer(tnode); if (tmpContainer.getType() == SINGLE) { string t = tmpContainer.getName();
[Code] ....
I cannot push_back(t). I examined the code with debugger, t has correct string value assigned, but even after 20-30 iterations, there is no element for headerFields vector.
I am trying to use push back in a 2D vector but I don't know how to. This is what I have:
vector <vector <BigInt> > matr;
for (BigInt i=0;i<rij;i++) { for (BigInt j=0;j<kolom-1;j++) { matr.push_back().push_back((i+1)^(pow-j)); } }
I quickly invented something but that doesn't work obviously. it should be equivalent to this: (the only problem in the code below is that those indexes don't exist yet that's why I need push_back())
for (BigInt i=0;i<rij;i++) { for (BigInt j=0;j<kolom-1;j++) { matr[int(i)][int(j)]=(i+1)^(pow-j); } }
Im creating a program for a race. The Race class has a vector of results and each element of that vector is a pointer to a result. The Result class has a Time and a pointer to a Participant. So in each race there are various results and it is a result for each participant.The Time is a class that has hours, minutes and seconds. How can I sort the vector of results from the result of the participant with the fastest time to the result of the participant with the slowest time?My code is like this:
//.h file: class Time { unsigned int hours; unsigned int minutes; unsigned int seconds;
Im creating a program for a race. The Race class has a vector of results and each element of that vector is a pointer to a result. The Result class has a Time and a pointer to a Participant. So in each race there are various results and it is a result for each participant. The Time is a class that has hours, minutes and seconds. How can I sort the vector of results from the result of the participant with the fastest time to the result of the participant with the slowest time?
Im getting some errors in my code. I put the error as comments in the code. Each error is after the line where it occurs. My code is like this:
How to avoid using Backspace character with push_back? I'm making a software as an ATM, so when the user try to enter the password the user only sees *******, but when trying to delete it doesn't delete a character. It just adds a new one. Here's my code:
Using SFML, I had a Board class which held multiple vectors of all of my object types in the game, and then it also held a vector of pointers to the memory addresses of these object instances, like this
class Board{ //... std::vector<AbstractObject*> GetAllLevelObjects(){ return allLevelObjects; } //so these are used to hold my object instances for each level
[Code]....
When looping through this vector and drawing the sprites of the objects, I get the runtime error 0xC0000005: Access violation reading location 0x00277000. I solved this error by storing the vector of pointers in the class that holds my Board instance, but I'm wondering why only this solution worked? Why couldn't I just have my vector of pointers in the same class that the instances of those objects were in?
I am creating code for a group project in my class. All my group members made a header file with an object in it with their functions. One of the functions in my partner's code uses a data member of mine in the function, so she has the function parameter a object of my object. (This isn't the code but for example)
class B { friend class A; void displayAthing(A object) { cout<<object.thing<<endl; }
I have this when I call the function in the cpp file
int main() { A object; B b; b.displayAthing(object); return 0; }
However, when I compile, it gives me an error that the function does not take 1 arguments.
I have a standard linked list in template format (with T being the typename) with the following relevant insertion operators:
bool PushFront (const T& t); // Insert t at front of list bool PushBack (const T& t); // Insert t at back of list
I want to build a list of pointers to objects (we'll call them objects of class Box for simplicity) that is member data for a parent class (we'll call that class Warehouse). However, I want to have a constant Box....const Box INVISIBLE_BOX = Box(); that represents a nonexistent Box. However, I cannot use either
PushFront(&INVISIBLE_BOX) or PushBack(&INVISIBLE_BOX)
to add INVISIBLE_BOX to the list of boxes without getting an invalid conversion error invalid conversion from âconst warehouse::Box*â to âwarehouse:: Box*â [-fpermissive]
What can I do to make it take a constant Box? I am using g++ to compile these files.
I have been experimenting with variadic templates with the aim of caching a call to a class method by storing away the object pointer, method pointer and parameters. I've actually had some reasonable success but have now hit a stumbling block. I now wish to wrap my parameters in a simple template class when I cache them. My success is as follows:
Using variadic template functions to store these pointers and paremeters;
I'm able to pass a method pointer and unwrapped parametersI'm able to pass wrapped parameters on their own.I'm NOT able to pass a method pointer and wrapped parameters I set up a little prototype project to demonstrate the issue and added comments above the function calls to indicate the compilation results. Here is the code:
Code: #include "stdafx.h" ////////////////////////////////////////////////// // Basic class with a simple method ////////////////////////////////////////////////// class MyClass { public: char Method( int i, float f ) { return 'A';
[code]....
But I'm convinced it should take three arguments, the method pointer and two wrapped parameters. Visual studio even suggested it should as shown below:
I'm able to convert an integer to a vector<unsigned char> and back. However, when I try to use a nearly identical function designed for the long long data type, the last byte or two is broken.
Program code:
long long num = 9223372036854775551LL; cout << "Before: " << num << endl; vector<unsigned char> data = getBytes(num); num = getLongLong(data); cout << "After: " << num << endl;
Code for converting between vector<unsigned char> and long long:
Code: vector<unsigned char> getBytes(long long value) { int bytes = sizeof(value); vector<unsigned char> data(bytes); for (int i = 0; i < bytes; i++) data.at(i) = (unsigned char)( value >> ((bytes-i)*8) );
I need to iterate through a vector in a const function, and, as my function is called very often, to get more performances I need my iterator to be declared somewhere else than the function, so it doesn't have to get deleted and recreated over and over again. So here is my code:
I have an array of pointers to Mat objects (an OpenCV class used to hold info and data about an image), which I will use to store the images. The function imread reads an image and returns a Mat object loaded with the relevant data about the image.However, this gives me a nice segfault when the assignment takes place. Of course, I can swap it with the following code, but since I'm working with big images (2048x2048 and upwards), it's really inefficient:
for(unsigned int i = 0; i < MAX_IMAGES; i++) { imageName[11] = 49 + i; datacube[i] = new Mat(imread(imageName, -1)); }
Is there any way to do this elegantly and without much hassle?Again, excuse my rustiness and anything completely stupid I might have said. It's been a long time since I worked with C++. Managed to circumvent the problem by using a STD vector instead of an array. I'd still like to know the answer to this riddle...
I have a data structure defined up here called this:
typedef list <classSpec*> ClassSpecList;
I'm trying to add stuff into the list here based on functions that return certain values of that match the same data type. In one function, I have a list pointer object defined here and I have another statement that calls a function.
Code: void Class1::Func(shared_ptr<type1> parameter) { } or void Class1::Func(const shared_ptr<type1>& parameter) { } or Should I ever pass arguments/parameters to other objects using shared_ptr's or raw pointers?
I've been really busy but managed to get in enough down time to learn somewhat decent info about vectors. Anyways originally my program created a dynamic array of pointers to class objects and I came across a few problems because of this. Apparently an array of pointers is now outta of the question and I will now be switching to a vector of objects instead.
Why I want a list of objects instead of pointers this little comment should clear things up.
tiles[i]->show() dereferences tiles[i] (i.e. accesses whatever it points at) before calling the show() method.
That is undefined behaviour. Once undefined behaviour occurs, there is no recovery, and there is nothing the show() method (or any subsequently called function for that matter) can do to recover (short of invoking their own forms of undefined behaviour - compiler specific hacks, etc).
Even if the show() method initialises the object correctly, it cannot change the pointer tiles[i] which is in a different scope (within main()).
What I'm trying to do is create a vector of already intialized objects so that I can use a conditional statement of every single element to properly layer my games art resources. This should also automatically fix a mild unrelated collision dectection problem too but first thing first layering.
here's the problem. I want to delete the objects within a vector, although I'm not sure whether I should clear the vector afterwards. Is it really necessary?
Code:
for (i = 0; i < allSales.size(); i++) delete allSales[i];
I have two classes, Parent and Child, where Parent contains a vector that is used to store instances of Child. When I create an instance of Parent, three instances of Child are also created in Parent's constructor and stored in the vector. I understand that push_back() creates a shallow copy of each Child instance and that Child's destructor is called each time the loop (inside Parent's constructor) iterates. The problem is that because Child's destructor is called each time the local variable child goes out of scope, the memory previously allocated in Child's constructor is destroyed and when Child's destructor is called again later on in the program to get rid of the copy stored in vector, the program crashes. I can fix this by overriding the default copy function or by storing pointers to objects instead of copies of objects. I don't really need to use vectors in this case since I always have three children in one parent but I'm doing this as a learning exercise and would prefer to use vectors.
I'm implementing kruskal's algorithm and ran into some troubles compiling. I need to sort a vector of objects by value. Here is my code and the error I'm getting.
Code:
These are the two functions in graph.cpp (there are more but are unrelated)
#include <vector> #include <algorithm> #include <iostream> using namespace std; #include "graph.h" #include "edge.h" using std::vector; void graph::sort_edgesArray() {
[code].....
//This is the error I'm getting.
graph.cpp: In member function "void graph::sort_edgesArray()": graph.cpp:39:33: error: no matching function for call to sort (std::vector<edge>::iterator&, std::vector<edge>::iterator&, <unresolved overloaded function type>) /usr/include/c++/4.5/bits/stl_algo.h:5236:18: note: candidate is: void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter = __gnu_cxx::__normal_iterator<edge*, std::vector<edge> >, _Compare = bool (graph::*)(edge&, edge&)]
