String vector iterator in c++

Question

I'm just trying to get the iterator over a vector of strings, getting the iterator passed to 'pos' and transfered together with the value at pos to another function, but the compiler tells me there was an invalid conversion at the lambda argument from 'const char*' to 'size_t'. I'm also getting this for header stl_algo.h:

no match for call to '(prototype::Monitor::setOptions(size_t)::<lambda(int)>) (const char &)' __f( __first);

#include <iostream>
#include <Windows.h>
#include <string.h>
#include <map>
#include <vector>
#include <algorithm>
#include <iterator>
#include <cstdio>
.
.
void setOptions(size_t id) {
    switch(id){
        case 0:
            std::for_each(main_menu.lines.begin(), main_menu.lines.end(),[this](size_t pos){
                this->setOption(pos, main_menu.lines[pos]);
            });
            break;
        case 1:
            break;
    }
}

Being all of these inside a class referred by 'this', and setOption is different from setOptions. I've read in other places that it should be fine if it would just convert the iterator for the string pointer to an int, i've also seen examples being used like that.

I also know this whole thing isn't probably the best way to do this, but i've just come to c++ and i'm trying to use some things i learned.

Win10 64bit - gcc (MinGW.org GCC-6.3.0-1)

Answer 1

When iterating a vector of strings with std::for_each() , the parameter passed to the lambda will be a string, not a size_t index. That is why you are getting a conversion error.

If you need an index, then you will have to change your lambda to track the index separately, eg:

size_t pos = 0;
std::for_each(main_menu.lines.begin(), main_menu.lines.end(),
    [&,this](const string &s){ this->setOption(pos++, s); }
);

Otherwise, simply don't use std::for_each() to begin with, eg:

for(size_t pos = 0; pos < main_menu.lines.size(); ++pos){
    setOption(pos, main_menu.lines[pos]);
}