C++ accessing element in vector of class objects

Question

I'm trying to access an element within a vector of class objects but I don't get it right. I guess it's something wrong with the constructor/deconstructor and reference but even the other questions like C++ destructor issue with std::vector of class objects, c++ vector of class object pointers or C++ vector of objects vs. vector of pointers to objects. Hopefully someone can help me to fix my code snippet.

node.h

class Node {

public:
    Node();
    Node(int id, const std::string& name);
    Node(const Node& orig);
    virtual ~Node();

    void cout(void);

    int get_id(void);

private:
    int _id;
    std::string _name;

};

node.cpp

#include "node.h"

Node::Node() {
}

Node::Node(int id, const std::string& name) : _id(id), _name(name) {
    this->cout();
}

Node::Node(const Node& orig) {
}

Node::~Node() {
}

void Node::cout(void) {
    std::cout << "NODE " << _id << " \"" << _name << "\"" std::endl;
}

int Node::get_id(void) {
    return _id;
}

communication.h

#include "node.h"

class Com {

public:
    std::vector<Node> nodes;

    Com();
    com(const Com& orig);
    virtual ~Com();

    void cout_nodes(void);

private:

};

communication.cpp

#include "communication.h"

Com::Com() {
    nodes.push_back(Node(169, "Node #1"));
    nodes.push_back(Node(170, "Node #2"));
}

Com::Com(const Com& orig) {
}

Com::~Com() {
}

void Com::cout_nodes(void) {
    for (uint8_t i = 0; i < nodes.size(); i++) {
        nodes[i].cout();
    }
}

If I run Com com; I get the expected output of:

[I 171218 13:10:10 Cpp:22] < NODE 169 "Node #1"
[I 171218 13:10:10 Cpp:22] < NODE 170 "Node #2"

but running com.cout_nodes(); results in:

[I 171218 13:10:14 Cpp:22] < NODE 0 ""
[I 171218 13:10:14 Cpp:22] < NODE 0 ""

As in C++ vector of objects vs. vector of pointers to objects everything works fine when I use references but I couldn't get std::iterator and find_if working than.

update: working `find_if` statement and index calculation

auto iterator = std::find_if(nodes.begin(), nodes.end(), [&](Node node) {
    return node.get_id() == 169;
});

if (iterator != nodes.end()) {
    size_t index = std::distance(nodes.begin(), iterator );
    std::cout << "Index of ID #169: " << index << std::endl;
}

StoryTeller - Unslander Monica · Accepted Answer · 2017-12-18T12:51:55.707

You defined this copy constructor:

Node::Node(const Node& orig) {
}

And it doesn't do any copying. It default initializes all the members of the Node being constructed. Since std::vector::push_back does a copy of its argument, your get bogus copies.

Rather than forcibly define an operation which the compiler can just as easily synthesize correctly by itself (you only have an int and a std::string as members), just don't declare it.

Or, if you do want to be explicit (or need to be, such as with the default c'tor), just explicitly default it:

class Node {

    Node()                 = default;
    Node(const Node& orig) = default;

};