Use a struct in another struct - c++

Hi there I keep getting error for the code below which I think makes sense!
I'm trying to use a member of the first struct in a function in the second struct. I code in Xcode and this is the error I get:
No member named 'PLZ' in 'std::__1::vector >'
#include <iostream>
#include <string>
#include <vector>
using namespace std;
struct place {
string PLZ;
string name;
};
struct adresse {
string firstN;
string lastN;
string Str;
string Hsnum;
string PLZ;
void print(vector<place> a){
cout<<a.PLZ;
}
};
int main()
{
return 0;
}


Just define the function at least like
void print(const vector<place> &a) const
{
for ( const auto &place : a )
{
cout << place.PLZ << ' ';
}
}
std::vector is a container that can contain several elements. So you have to specify whether you are going to output all elements of a vector or a concrete element.
The function above outputs the data member PLZ of each element of the vector.

Related

C++ creating a std::vector from std::string array

I am learning about c++ and was following a course. A final exercise involves making a program for deck of cards. I have thought of an approach:
I initially tried to do everything with string arrays but realised that it would make more sense to use vectors since. I am now trying to create a std::vector std::string out of my std::string array but with no luck.
I have found some example code online such as:
from https://thispointer.com/5-different-ways-to-initialize-a-vector-in-c/
And tried to implement it for my program, however, I cannot get it to work and cant fully understand what is the issue.
My code:
#include <iostream>
#include <string>
#include <vector>
class card_deck {
public:
card_deck();
std::vector<std::string> deal_hand(int num_cards);
void new_deck();
private:
//std::vector<std::string> cards_vector;
std::string cards[52] =
{
"As","2s","3s","4s","5s","6s","7s","8s","9s","Ts","Js","Qs","Ks",
"Ah","2h","3h","4h","5h","6h","7h","8h","9h","Th","Jh","Qh","Kh",
"Ad","2d","3d","4d","5d","6d","7d","8d","9d","Td","Jd","Qd","Kd",
"Ac","2c","3c","4c","5c","6c","7c","8c","9c","Tc","Jc","Qc","Kc"
};
std::vector<std::string> cards_vector(cards, sizeof(cards)/sizeof(std::string) );
};
As you can see from my code, I initialize a string array in my private variables, and then want to convert this string array to std::vector
The error message returned:
UPDATE
Code works when called in main()
int main()
{
std::string cards[52] =
{
"As","2s","3s","4s","5s","6s","7s","8s","9s","Ts","Js","Qs","Ks",
"Ah","2h","3h","4h","5h","6h","7h","8h","9h","Th","Jh","Qh","Kh",
"Ad","2d","3d","4d","5d","6d","7d","8d","9d","Td","Jd","Qd","Kd",
"Ac","2c","3c","4c","5c","6c","7c","8c","9c","Tc","Jc","Qc","Kc"
};
// Initialize vector with a string array
std::vector<std::string> vecOfStr(cards, cards + sizeof(cards) / sizeof(std::string));
for (std::string str : vecOfStr)
std::cout << str << std::endl;
}
Does not work when used in class
#include <iostream>
#include <string>
#include <vector>
class card_deck {
public:
card_deck();
std::vector<std::string> deal_hand(int num_cards);
void new_deck();
private:
std::string cards[52] =
{
"As","2s","3s","4s","5s","6s","7s","8s","9s","Ts","Js","Qs","Ks",
"Ah","2h","3h","4h","5h","6h","7h","8h","9h","Th","Jh","Qh","Kh",
"Ad","2d","3d","4d","5d","6d","7d","8d","9d","Td","Jd","Qd","Kd",
"Ac","2c","3c","4c","5c","6c","7c","8c","9c","Tc","Jc","Qc","Kc"
};
// Initialize vector with a string array
std::vector<std::string> vecOfStr(cards, cards + sizeof(cards) / sizeof(std::string));
for (std::string str : vecOfStr)
std::cout << str << std::endl;
};
int main()
{
}

Easy way:
std::vector<std::string> cards {
"As","2s","3s","4s","5s","6s","7s","8s","9s","Ts","Js","Qs","Ks",
"Ah","2h","3h","4h","5h","6h","7h","8h","9h","Th","Jh","Qh","Kh",
"Ad","2d","3d","4d","5d","6d","7d","8d","9d","Td","Jd","Qd","Kd",
"Ac","2c","3c","4c","5c","6c","7c","8c","9c","Tc","Jc","Qc","Kc"
};
and drop the separate cards_vector member. cards.size() yields the number of elements in the vector.
This uses the initialiser-list syntax of C++11.
And the compiler works out the size for you: handy if you need to add the jokers in later for example.

Structure Arrays & Pointers

I have to use a struct array called Robot_parts[] for each part_rect struct (part_num, part_name, part_quantity, part_cost)
And through the void display function, I have to display Robot_parts[] array entirely through pointer but I don't know how, and I don't know where to declare Robot_parts[] and whether i have to put any number value inside the brackets.
So far I have:
#include <iostream>
#include <string>
using namespace std;
void display();
struct part_rec
{
int part_num;
string part_name;
int part_quantity;
double part_cost;
};
int main()
{
part_rec Robot_parts[ ] = {
{7789, "QTI", 4, 12.95},
{1654, "bolt", 4, 0.34},
{6931, "nut", 4, 0.25}
};
return 0;
}
void display()
{
cout<<Robot_parts[]<<endl<<endl;
}
If I also made a few other errors, please let me know. Thanks!

As stated in a comment it would be much better to use a c++ container like a std::vector or std::array.
But since your professor requires an old-style array, you could try like the code below - see the comments for explanation:
#include <iostream>
#include <string>
#include <vector>
using namespace std;
struct part_rec
{
int part_num;
string part_name;
int part_quantity;
double part_cost;
};
// You have to pass a pointer (to the array) and the size of the array
// to the display function
void display(part_rec* Robot_parts, int n);
// Make a function so that you can "cout" your class directly using <<
// Note: Thanks to #BaumMitAugen who provided this comment and link:
// It makes use of the so called Operator Overloading - see:
// https://stackoverflow.com/questions/4421706/operator-overloading
// The link is also below the code section
std::ostream &operator<<(std::ostream &os, part_rec const &m)
{
// Note - Only two members printed here - just add the rest your self
return os << m.part_num << " " << m.part_name;
}
int main()
{
part_rec Robot_parts[] {
{7789, "QTI", 4, 12.95},
{1654, "bolt", 4, 0.34},
{6931, "nut", 4, 0.25}
};
display(Robot_parts, 3);
return 0;
}
void display(part_rec* Robot_parts, int n)
{
// Loop over all instances of your class in the array
for (int i = 0; i < n; ++i)
{
// Print your class
cout << Robot_parts[i] << endl;
}
}
The link recommended by #BaumMitAugen:
Operator overloading

How Do I Store Objects in a Object in a Vector? (C++)

I hope this is not a stupid question. Basically I would like to access a string stored in a Class (Statement is the name I am using) in a vector of type Statement. Basically I am trying to store objects in a dynamic hierarchy of objects.
Types.cpp:
#include<iostream>
#include<fstream>
#include <string>
#include <vector>
using namespace std;
class Statement{
public:
vector<string> Inner_String;
vector<Statement> Inner_Statement;
string contents;
void set_contents (string);
string get_contents(){ return contents;}
void new_string(string);
string get_string(int v){return Inner_String[v];}
void new_Inner_Statement(Statement);
Statement get_Inner_Statement(int v){return Inner_Statement[v];}
};
void Statement::set_contents(string s){
contents = s;
}
void Statement::new_string(string s){
Inner_String.push_back(s);
}
void Statement::new_Inner_Statement(Statement s){
Inner_Statement.push_back(s);
}
Main method:
#include <iostream>
#include "FileIO.h"
#include "Types.h"
using namespace std;
int main()
{
Statement test;
test.new_Inner_Statement(Statement());
Statement a = test.get_Inner_Statement(0);
a.set_contents("words");
cout << a.get_contents();
test.get_Inner_Statement(0).set_contents("string");
cout << test.get_Inner_Statement(0).get_contents();
return 0;
}
What happens is
cout << a.get_contents()
returns its string while
cout << test.get_Inner_Statement(0).get_contents()
does not.

Look at this piece of code:
test.get_Inner_Statement(0).set_contents("string");
^^^^^^^^^^^^^^^^^^^^^^^^^^^
It calls this function:
Statement get_Inner_Statement(int v)
which returns a copy object (temporary) of type statement. On this object, you calls set_contents function, at which cease to exists at the end of the call.
Then, you call:
test.get_Inner_Statement(0).get_contents();
that creates a new temporary, from the unchanged statement, and try to get its contents.

C++ Error: Was not declared in the scope

Hey guys I'm working on a project and I was doing pretty well until I hit this wall..
I am getting two errors:
error: 'binarySearch' was not declared in this scope
error: 'addInOrder' was not declared in this scope
Here are my files, I've tried quite a few things with no avail. Help would be much appreciated.
histogram.cpp
#include "histogram.h"
#include "countedLocs.h"
//#include "vectorUtils.h"
#include <string>
#include <vector>
using namespace std;
void histogram (istream& input, ostream& output)
{
// Step 1 - set up the data
vector<CountedLocations> countedLocs;
// Step 2 - read and count the requested locators
string logEntry;
getline (input, logEntry);
while (input)
{
string request = extractTheRequest(logEntry);
if (isAGet(request))
{
string locator = extractLocator(request);
int position = binarySearch (countedLocs,
CountedLocations(locator, 0));
/** Hint - when looking CountedLocations up in any kind
of container, we really don't care if the counts match up
or not, just so long as the URLs are the same. ***/
if (position >= 0)
{
// We found this locator already in the array.
// Increment its count
++countedLocs[position].count;
}
else
{
// This is a new locator. Add it.
CountedLocations newLocation (locator, 1);
addInOrder (countedLocs, newLocation);
}
}
getline (input, logEntry);
}
// Step 3 - write the output report
for (int i = 0; i < countedLocs.size(); ++i)
output << countedLocs[i] << endl;
}
countedLocs.cpp
#include "countedLocs.h"
#include <iostream>
#include <vector>
using namespace std;
int CountedLocations::binarySearch(const vector<CountedLocations> list, CountedLocations searchItem)
{
//Code was here
}
int CountedLocations::addInOrder (std::vector<CountedLocations>& vectr, CountedLocations value)
{
//Code was here
}
countedLocs.h
#ifndef COUNTEDLOCATIONS
#define COUNTEDLOCATIONS
#include <iostream>
#include <string>
#include <vector>
struct CountedLocations
{
std::string url;
int count;
CountedLocations (){
url = "";
count = 0;
}
CountedLocations(std::string a, int b){
url = a;
count = b;
}
int addInOrder (std::vector<CountedLocations>& vectr, CountedLocations value);
int binarySearch (const std::vector<CountedLocations> list, CountedLocations searchItem);
};
inline
std::ostream& operator<< (std::ostream &out, CountedLocations& cL)
{
//out << "URL: " << cL.url << " count: " << cL.count << std::endl;
out << "\"" << cL.url << "\"," << cL.count;
return out;
}
#endif

The methods are member methods of CountedLocations... use something.extractLocator and something.binarySearch or make the histogram() to be also a member method of CountedLocations... (something is of type CountedLocations highly possibly will be countedLocs[position])

You have a free function histogram in which you are trying to use two member functions, addInOrder and binarySearch. In order to use them, you need to have an instance of CountedLocations.
If these are some kind of helper functions, which do not depend on the actual CountedLocations instance, I would turn them into static functions like this (you only need to change the header):
static int addInOrder (std::vector<CountedLocations>& vectr, CountedLocations value);
And then you can call this function by specifying the type of your class:
CountedLocations::addInOrder(...);

You are trying to call member methods of a struct without an object of that type. Strange.

You need to look at what a namespace is.
You declare a class CountedLocations, so far so good. But then you try to use the member functions outside the CountedLocations namespace which will obviously never work.
int position = binarySearch (countedLocs,
CountedLocations(locator, 0));
binarySearch is a member function of the CountedLocations namespace. If you want to call that function you have to create an object that contains a reference to that member function.
CountedLocation myObject;
int position = myObject.binarySearch (countedLocs, CountedLocations(locator, 0));
I dont know if that solves your problem, but you should know this before you even attempt to solve a problem.

Calling a member function pointer stored in a std map

I'm storing a map in a class that has strings as keys and pointers to member functions as values. I'm having trouble calling the right function throw the function pointer.
Here is the code:
#include <iostream>
#include <string>
#include <map>
using namespace std;
class Preprocessor;
typedef void (Preprocessor::*function)();
class Preprocessor
{
public:
Preprocessor();
~Preprocessor();
void processing(const string before_processing);
private:
void take_new_key();
map<string, function> srch_keys;
string after_processing;
};
Preprocessor::Preprocessor()
{
srch_keys.insert(pair<string, function>(string("#define"), &Preprocessor::take_new_key));
}
Preprocessor::~Preprocessor()
{
}
void Preprocessor::processing(const string before_processing)
{
map<string, function>::iterator result = srch_keys.find("#define");
if(result != srch_keys.end())
result->second;
}
void Preprocessor::take_new_key()
{
cout << "enters here";
}
int main()
{
Preprocessor pre;
pre.processing(string("...word #define other word"));
return 0;
}
In function Preprocessor::processing if the string is found in the map then, I call the proper function. The problem is that, in this code, Preprocessor::take_new_key is never called.
Where is the mistake ?
Thanks

The correct syntax is this:
(this->*(result->second))();
That is ugly. So lets try this:
auto mem = result->second; //C++11 only
(this->*mem)();
Use whichever makes you happy.

result->second does not call the function pointer. Try ((*this).*result->second)();