C++ :: Compare Data Members Of Objects Store In Vector
Mar 6, 2014
Overview of problem : I am using std::vector to hold objects of Subject. Now this vector contains lots of objects( with lots I mean 10-20 objects at max) . These objects have string member values like category and sub_category. Both category and sub_category can have string which can be same of other objects's sub_category & category.
Issue: Now I want my std::vector to have only those objects whose's sub_category are unique. If category is not unique that's not a problem .
Secondly if we found 2 objects having same sub_category then we have to delete one of them from the vector. we will delete it based on some rules example
Rules for deleting are if
i) instance of Subject ->category = " Land " OR if category = "Jungle" then delete other duplicate object ,
ii) if above condition doesn't match then delete either of them.
I am wondering , how would I compare the sub-items from the vector . For example. I have class say Subject
class Subject {
public :
// some constructors,
// functions to get ., set category and sub category
std::String get_sub_category()
std::string get_category();
private:
std::string category;
std::string sub_category;
}
I have vector which stores object of Subjects. Example : vector<Subject> copy_vector;
Now what I want is to delete the object from vector that has same sub_category I am not looking for source code buT i need a starting point,? Example:
copy_vector[0] = Animal object that has sub_category Tiger
copy_vector [1] = Animal object with Lion as sub category
copy_vector[2] = Forest object with sub_category Tiger
What I want is to based on some conditions(which I can do ) remove either Forest or Animal object containing Tiger. But for that how would I do comparison? I have written the function and have checked it.
std::vector< Subject >copy_vector;
// copy_vector contains all the objects of Subject with redundant sub_category
for( std::vector< Subject >::iterator ii = copy_vector.begin() ; ii != copy_vector.end() ; ++ii ) {
sub_category = ii->get_sub_category();
The program is supposed to read a formatted .txt file and store the data into their respective [Class] Members. It will then output the data collected onto screen.I overloaded ifstream and istream. When I call for file>>ptr[i] to read the data, something goes wrong. It prompts me to input data (which is in istream overload).The Data in .txt file is as follows;
Running into a snag in my program. I can't seem to figure out how to have an object of a class be able to look at all the other objects of its own class.
Reasoning being, I'm working on a game with multiple ships flying around in the same space. Each ship is a class. Each ship has an x and a y, and needs to compare the angle and distance of other ships' x and y coordinates to see if they're visible on the same screen.
How to tell an object to look at objects of its own class.
Here's some code:
common.h
#ifndef COMMON_H_INCLUDED #define COMMON_H_INCLUDED int dist(int x1, int y1, int x2, int y2); int get_info(int which);
[Code] ....
Basically, I just don't know how to properly write a function, call, or how to get the info I need, to the Player::get_closest() function so that it can see the other play objects.
I have code working, but that is largely because a vector that I am using as part of a structure that is the first of two elements of a MAP (with the second being an integer that is assigned later) is serving in its original, purely vector form, to fill out a set of selections on a DOS screen (option 1, 2, 3, etc.).
I do use the MAP, because it is a simple means of referencing the integer value using a word that is part of the structure, and is probably appropriate, saving me a search through the vector of words and calling up the value at the same location in the vector of words in a vector of corresponding numerical values. I DO feel that what I'm doing to produce the selection list is something of a "cheat" because I do not know how to access the same data within the structure component of the MAP by simply using a similar numerical reference (e.g. "MAP[1].structure.word", or would that be "MAP.structure.word[1]" ????) to print out the words in the structure in the map as choices on the screen.
I don't want to change or expand the contents of the map, just access and print each one in a simple loop with a number from the loop counter to the left of each word.
I've started programming my little program called vLibrary (program I want to make for the library in my city) and after I m done with console application I will try to implement wxWidgets.My program will be able to add new users to the system, new books and new librarians.
Now, I m confused what data types to use and how to store objects (newly created users, books etc) to my program so later on they can log in the system etc. Logic of the program is completely clear to me but I m not sure how to make array of objects and store them in memory or in a certain file, how to store password and make some kind of encryption etc.which data structure from STL should I use and how.
I'm using the SDL library and trying to match the C++11 standards... Anyway, I thought about a vector where I store all the addresses of game instances, so I can access them anytime... I tried with this function:
Where "Instance" is the 'parent' class of various child classes like the player. So, if I have to search the existing of a thing in my game, I should check if the address references to an instance of class. How can I do this?
Okay, I'm not entirely certain where my code is messed up, but when I run the console it asks if I want to add Employee information and then it just skips through everything when I say yes.
I have a paradigm where a integer before gets enqueued to a queue in a vector, the loop of queues is searched and integer is enqueued to a queue which has minimum size among the queues. the following code shows the operation
next i am trying to extend my paradigm with the condition, that the integers should be enqueued to the shortest queue until the count of the shortest queue is less than or equal to count of any another queues in the loop of queues.
I would like to compare two strings, one of which is an independently stored string - the other being a string within a vector. However, i do not know how to do this, as
How do I compare a string vector against an enumerated type? My code so far is:
void convertToLastFirst(vector<string>&names){ enum NameFormat{FIRST, LAST}; for (size_t i = 0; i < names.size(); i ++){ if (names[i] FIRST){ names[i] = LAST; } } }
I'm trying to put file data into members of a class. Remember to type in the file name you want to open. Cool feature right? I just had Dbase.txt so I chose that.
Fixed stuff in the .txt. Now I need to figure out why it only does 1 set and then ends.
#include <cstdio> #include <cstdlib> #include <iostream> #include <fstream> using namespace std; class INFO {
[Code] .....
Dbase.txt: Bob Guy Programmer M 9999.99 40 ------------------ Little Guy Little Brother M 0.0 3 ------------------
All the undos and redos were working fine until the pointer data members came into the picture. The problem is that the values pointed to changed, but the pointers themselves did not. So restoring gives the same pointers but they still point to the new values. I think the solution is that the classes that are the pointer data members themselves need their own Mementos (which would be a lot of work because there are many data member pointers in my program). Is that the only approach?
Here is a sample code to show what I'm talking about. You can compile and run the program to see the problem it has restoring values of pointer data members:
I am to first increment data members of object that has not created dynamically (i have done with this part),now i have created object dynamically and how to increment its data which i have passed as argument as:
Is it generally better to initialize string data members as nullptr or as a zero-size array?
I can understand the former is superior from a memory-use perspective and also not requiring the extra allocation step. However, many string management functions will throw an exception - wcslen for instance - if you pass them a null pointer. Therefore I am finding any performance gained is somewhat wiped out by the extra if(pstString==nullptr) guards I have to use where it is possible a wchar_* may still be at null when the function is called.
I have written the following code to add data to text files which are required to store 3D scan data (I have to calculate the y-coordinate). My code seems to work except that it stops working when I want to create more than ten text files i.e. the directory I am trying to store them in will not hold any more than ten text files. Code is shown below.
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.
