C++ :: Function That Brings In A Stream Object
Sep 23, 2014
I'm supposed to add two new functions to an existing class that I've written early on: readData(ifstream&)and writeData(ofstream&).
The parameters of the program are:
-Create three employee objects as shown,
-Create an ofstream object and open a file. Choose any name for the file that you want. Do not ask the user for the file name. Pass just the file name as the parameter (no path) so that your program assumes the file to be in the same folder as your executable file.
-Send messages to each of the three Employee objects to write themselves out to the file.
-Close the file.
...
If I get writeData(ofstream&) function bit to work! for brevity I've cut all the functions of the class that arent necessary. Here's what I have so far:
Employee.h
#pragma once
#include<string>
using namespace std;
[Code] ....
So I've tried a bunch of different ways to get my objects into the ofstream object to write them to the file, but I'm supposed to use the two new functions somehow...but I'm way lost.
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Dec 8, 2013
How to get this thing to work. All i need to do is ask user to input a name and then it brings out the line from the .txt file containing the information.
For example in my case I'm doing a member search function I'm required to ask user to input the name of the customer and then print out all the details (which consumes 1 text line in the .txt file)
Here is the code, This is the write to text file method (100% working)
Code:
cout << "Customer Name: ";
cin >> name;
// ...
ofstream myfile("customer.txt", ios::app);
[Code] .....
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May 5, 2014
I need to create a function in my program to open an input file and another function to open an output file and I need to use the files in other functions so Im trying to pass the stream object by reference but then i need a condition that tells the compiler not to reopen the file because then it will delete everything and make me input the file names again. Heres the two functions.
void InputFileOpen(ifstream &inFile) {
string file_name;
if(!inFile.is_open()){
cout<< "Enter the input file name: ";
cin>> file_name;
inFile.open(file_name, ios::in);
[code]....
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Jan 21, 2014
I have two puzzling issues I am dealing with.
Issue 1: I am using a stringstream object in a block of my program that needs to be visited repeatedly depending on a user's selection from a menu. I want the contents of this stringstream object to be cleared any time control gets to this part of the program. I have tried the clear and flush functions to no avail.
Issue 2: I am reading data from a source text file that would be regularly changed during the course of program run. After the program run is over, I am supposed to save the results(which is basically the source text file AND all updates) in a destination file. This destination file would then serve as the source file when next the program is run. In other words, I want a scenario where my results overwrite the original contents of the source file; implying that my source and destination files are now one, pretty much. How can I do this?
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Jul 26, 2012
Try to implement overloading << operator. If I done it void then everything work fine (see comment out) if I make it class of ostream& then the operator return to me some memory address.
Code:
#ifndef Point_HPP // anti multiply including gates
#define Point_HPP
#include <sstream>
class Point {
private:// declaration of private data members
double x;// X coordinate
double y;// Y coordinate
[Code] .....
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Apr 29, 2013
I wrote a program to write text contents to file stream through fputs, the file stream address was changed in the middle of writing text content to the stream (11% text content have been put into the file stream), that cause the file stream pointer can be evaluated problem and raise exception on stream validation code in fputs library function, my question is what things could go wrong to make file stream pointer changed its address to something else or a NULL pointer if the file stream have not been flushed and closed.
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Jan 15, 2013
On fairly rare occasions, when attempting to debug one of my MFC applications on VS 2010, a compilation error is encountered, and instead of bringing up the customary Windows or MFC file with a arrow pointing to the problem, a disassembly appears with an arrow pointing to one of the assembler instructions.
Since Windows assembly language is hardly my forte, I do not know how to interpret the error. Furthermore, the Output usually indicates one or more 'first chance exceptions' but little more, and the Stack output usually quite sparse and often refers cryptically to some ntdll.dll!7c92a82c().
How can I better define the compile error?
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Apr 26, 2012
I have function which will replace (or create) an file with the contents of another stream. The stream could be anything. The replacement is done safely.
Code:
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <limits.h>
#include <unistd.h>
int do_replace(const char *file, int stream, int cnt) {
[Code] .....
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Jun 27, 2014
I would like to have 2 functions. (FYI, I haven't even tested these because I don't have a compiler on this PC, so don't know what they'll do. I'm also new to C++, self-teaching.)
My question is, I'm sure that oFile should be type object (of some sort), not int, but I'm not sure how to reference it correctly so that it passes from FileOpen to main to FileClose.
Code:
#include <iostream> //I/O
using namespace std;
#include <fstream> //files
using namespace ios;
int FileOpen(string fileName) {
ifstream oFile (fileName); //attempt to open file
[Code] ....
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Feb 13, 2013
This is supposed to check for valid input
if(((c.integer < 0)&&(c.numerator < 0))||(c.denominator<=0)) {
c.integer = 0;
c.numerator = 0;
c.denominator = 0;
}
if((c.integer>0)&&(c.numerator<0))
[Code] ....
And it does just fine, until it's passed into a function, then it doesn't work:
void validInput(Mixed a) {
if(((a.integer < 0)&&(a.numerator < 0))||(a.denominator<=0)) {
a.integer = 0;
a.numerator = 0;
a.denominator = 0;
[Code] ....
It works, when the object is passed, except for two cases (one where the minus sign shifts) and whenever there is a zero or a negative integer in the denominator.
Also, I'm passing the function like validInput(c);
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Apr 12, 2013
i need to pass myboard.board (board is in the class Cboard and it is an array of int) to a function in a class called piece however this is troubling . i need to pass it as pointer os that i could change its value here under is my code.
main.cpp Code: #include<iostream>
#include"board.h"
#include "pieces.h"
[Code].....
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Jan 18, 2013
I am trying to build a function with an array object as argument. Please see the following code:
// main.cpp
const int a = 10;
......
//function.cpp
void test_func(double x, array<double, a> &y) {
......
}
This code cannot be compiled because the "a" in parameter is not identified. I cannot neither put const int a as argument to the function.
Here I need "a" to control size of the array from the main.cpp. How can I make this work?
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May 30, 2013
I'm making a code that uses a Function pointer. The problem is, when I try to compile appears an error like:
error: no matching function for call to 'rnVector::rnVector()'
Here's part of the code:
phiFunction::phiFunction(double (*f)(rnVector), rnVector (*df)(rnVector)) {
//... Here comes the code stuff...
}
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May 21, 2014
Is it correct for me to make a clone of testobj in function AddTest below, before i add it to my map? What i want is an user pass testobj to me though AddTest, and after i add it into my map, i do not want to have anything to do with the original testobj anymore. I.e, they are two copies, one belong to Device, one belong to the caller, both has no link to each other.
Also regarding the GetTest method, i prefer to return a raw pointer, as i do not want to force the caller to use smart pointer. And i also do not want the caller to be able to do anything that may change testobj in the map. So i am not sure to return as const reference or make a clone of testobj on the map and return it to the user (but caller need to delete the testobj when it is not used).
Code:
class Device {
public:
void AddTest(const Test* const testobj) {
_pTest.insert("ss", QSharedPointer<Test>(test->clone()));
} const Test* const GetTest(QString str) {
return _pTest[str].data();
[code].....
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Nov 24, 2013
Code:
class Main{
class B b_obj;
C c_obj=b_obj.test("some",89); // I cannot get this done.!
}
Below are .h files:
class B{
public:
C* test(const char *, int); /// this doesn't work
constructor
//member variables
[Code] ....
However, map<string, vector<bol>> test(const char *, int); works.I know second thing will work, but how to take reference of class object?
I have include .h file in main, B and C, wherever it is required.
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May 20, 2014
I have a Qt classes as follow:
Code:
class Vehicle {
public:
void AddData(QString str, Data* data) {
_myDataMap.insert(str,data);
} virtual void Init();
[code].....
My questions are:
After the main function called d1->Modify; the data stored in _myDataMap will get modified too.
What is the more appropriate way of passing the Data through AddData in such case?
If i do AddData(const Data & data), i will not be able to use inheritance of Data, i.e passing a subclass of Data to AddData.
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Jul 6, 2013
I want my function to take 'fstream' object as an input, so the program looks like this:
Code:
#include <fstream>
using namespace std;
void test(fstream a){
a.open("test2.txt");
a << "123" << endl
[Code] ....
But I get error: 'std::ios_base::ios_base(const std::ios_base&)' is private|
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Nov 26, 2013
I have the following piece of code.
Code:
#include<iostream>
using namespace std;
class Test {
public:
Test(){cout<<"Test"<<endl;}
void fun() {
int i=5;
[Code] ...
Compiled with g++.
Executing this give output fun5.
It is correct? I have not allocated any object and so this pointer is not created. Then how it is able to run and call the function.
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Oct 30, 2014
while(!secList.empty()){
Security se = Security();
se = secList.extract(); // CRASH
cout << "Security info: " << se.security << endl;
cout << "Transaction List: " << endl;
while(!se.tranList.empty()){
Transaction tr = Transaction();
[code]....
my program crash when it try to assign the return value of the function to the local value. extract function does return correct value, but it just crash when done executing.
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Feb 21, 2013
I have a school project in which need to create a function that takes a File Object as a Reference Parameter. Supposedly, it should allow me to read the first piece of data from others separated by a space from a file. The later be able to continue reading from the next piece of data.
I know how to set things up to read from the data file, such as using
Code:
#include <iostream> , and
Code:
ifstream inputFileName;
inputFile.open ("nameOfFile");
I also understand how to pass a variable by reference to a function. But I simply cannot put the two items together!
I tried using
Code:
void getFileInput (ifstream &); //parameter
getFileInput ("nameOfFile") // call
void getFileInput (ifstream &dataFileName)
In the function I used
Code:
ifstream inputFile;
inputFile.open (dataFileName);
I'm just not getting an understanding of this concept!
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Feb 23, 2015
Write a function named replaceSubstring. The function should accept three C-string or string object arguments.
Let's call them string1, string2, and string3. It should search string1 for all occurrences of string2. When it finds an occurrence of string2, it should replace it with string3.
For example, suppose the three arguments have the following values:
string1: "the dog jumped over the fence"
string2: "the"
string3: "that"
With these three arguments, the function would return a string object with the value "that dog jumped over that fence." Demonstrate the function in a complete program.
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Feb 23, 2014
I'm trying to write a function for receiving messages, so my classes can communicate with each other. The only issue I get is a compile error asking me to define the base parameter as one of the derived instances. I tried using a void* to fill the need, but then I lose the initial type, which I need to check for. How might I go about writing a generic object for this?
Here's my code:
template<class Object>
class State
{
public:
[Code].....
Should I just have all of the objects inherit in the order of Object >> GenericObject >> DerivedObject?
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Jul 29, 2014
I have found that when I dump a C++ object from memory to a file - it seems that there is a misplacement of the last Virtual-Function-Table pointer - in that appears at the beginning. The result is that the gdump information based on this object dump (using green hills) is incorrect. I copied the contents of the gdump information below. The executable is compiled in linux.
Basically MEIO::CameraStatus contains an item that relates to its parent class (line 188). Then it has 18 items that are all Diagnostics::EventsCounter items. Now for each Diagnostics::EventsCounter item there is a Virtual-Function-Table Info Pointer as its last item. All is fine and good except that the last item of MEIO::CameraStatus which is _selfReset is missing its last item of 4 bytes (which is the Virtual-Function-Table Info Pointer ). On the other hand - right before the first Diagnostics::EventsCounter item ("_vidErrors") - there is an extra 4 bytes which happens to be the Virtual-Function-Table Info Pointer. As I said the gdump information file does not see this.
Why the object memory "moves" the last Virtual-Function-Table Info Pointer to the beginning (right before _vidErrors) and is there a way to "fix" this?
///////////////////////////////////////////////////////////////////////////
"MEIO::CameraStatus" val:0x000002f0 ind208,-1) Struct-Begin Info
188: "" offset 0, Parent-Class Private Info C++ Struct ref = 114
189: "_vidErrors" offset 160, Member Info C++ Struct ref = 128
190: "_vdiErrors" offset 480, Member Info C++ Struct ref = 128
[Code] .....
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Nov 7, 2013
#include <iostream>
#include <cstdlib>
#include <time.h>
#include <conio.h>
using namespace std;
class Dice {
[Code] ....
Every time the roll_dice function get call twice for the same object, i receive the same dice values.
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Aug 12, 2013
I know what are pointer's and how to use them but there is one point i am not able to understand. Below is the example code
I understand everything in the below code except 1 thing why i am using pointer to base class object in vector int the main() Function?
Code:
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
// base class
[Code] ...
Here is the lines of code i want to understand.
Code:
vector<Employee*> employees;
employees.push_back(&emp1);
employees.push_back(&mgr1);
I know if i will not use the pointer base class function "virtual double grossPay" will be called for both base class object and derived class object and when i will use pointer with reference to the object because base class function is virtual it will look for same function in derived class and if available it will execute it.
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Mar 16, 2013
will copy constructor does object initialization using another already created object? I understand that it can be applied for object initialization and not for assignment.Is it correct?
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