I want to check whether an element exists in the vector or not. I know the below piece of code will check it.
#include <algorithm>
if ( std::find(vector.begin(), vector.end(), item) != vector.end() )
std::cout << "found";
else
std::cout << "not found";
But I have the vector of any type. i.e. std::vector<std::any>
I am pushing elements into vector like this.
std::vector<std::any> temp;
temp.emplace_back(std::string("A"));
temp.emplace_back(10);
temp.emplace_back(3.14f);
So I need to find whether string "A" present in the vector or not. Can std::find help here?
As of now I am using below piece of code to do this
bool isItemPresentInAnyVector(std::vector<std::any> items, std::any item)
{
for (const auto& it : items)
{
if (it.type() == typeid(std::string) && item.type() == typeid(std::string))
{
std::string strVecItem = std::any_cast<std::string>(it);
std::string strItem = std::any_cast<std::string>(item);
if (strVecItem.compare(strItem) == 0)
return true;
}
else if (it.type() == typeid(int) && item.type() == typeid(int))
{
int iVecItem = std::any_cast<int>(it);
int iItem = std::any_cast<int>(item);
if (iVecItem == iItem)
return true;
}
else if (it.type() == typeid(float) && item.type() == typeid(float))
{
float fVecItem = std::any_cast<float>(it);
float fItem = std::any_cast<float>(item);
if (fVecItem == fItem)
return true;
}
}
return false;
}
This should work good I guess:
#include <vector>
#include <string>
#include <any>
#include <algorithm>
#include <iostream>
int main(){
std::vector<std::any> temp;
temp.emplace_back(std::string("A"));
temp.emplace_back(10);
temp.emplace_back(3.14f);
int i = 10;//you can use any type for i variable and it should work fine
//std::string i = "A";
auto found = std::find_if(temp.begin(), temp.end(), [i](const auto &a){
return typeid(i) == a.type() && std::any_cast<decltype(i)>(a) == i;
} );
std::cout << std::any_cast<decltype(i)>(*found);
}
Or to make the code a bit more generic and reusable:
#include <vector>
#include <string>
#include <any>
#include <algorithm>
#include <iostream>
auto any_compare = [](const auto &i){
return [i] (const auto &val){
return typeid(i) == val.type() && std::any_cast<decltype(i)>(val) == i;
};
};
int main(){
std::vector<std::any> temp;
temp.emplace_back(std::string("A"));
temp.emplace_back(10);
temp.emplace_back(3.14f);
//int i = 10;
std::string i = "A";
auto found = std::find_if(temp.begin(), temp.end(), any_compare(i));
std::cout << std::any_cast<decltype(i)>(*found);
}
Live demo
Important note: this is guaranteed to work only within single translation unit due to stadard requirements on std::any
type (for example same types don't need to have same type identifier in different translation units)
Comparison with typeId()
should be avoided since it's dependent from translation unit.
A much safer approach can be used with any_cast
of pointers:
template<typename T>
std::optional<T> find(const std::vector<std::any>& v)
{
for(auto&& e : v){
if(auto ptr = std::any_cast<T>(&e)){
return *ptr;
}
}
return std::nullopt;
}
Find first element with the given type, or nullopt
if it's not found.
If we want to find all element with a specific instead:
template<typename T>
std::vector<T> findAll(const std::vector<std::any>& v)
{
std::vector<T> out;
for(auto&& e : v){
if(auto ptr = std::any_cast<T>(&e)){
out.push_back(*ptr);
}
}
return out;
}
Usage:
int main()
{
std::vector<std::any> temp;
temp.emplace_back(std::string("A"));
temp.emplace_back(10);
temp.emplace_back(3.14f);
temp.emplace_back(12);
temp.emplace_back(std::string("B"));
auto outInt = findAll<int>(temp);
std::cout << "out int: " << outInt.size() << std::endl;
for(auto&& out : outInt)
std::cout << out << std::endl;
auto outString = findAll<std::string>(temp);
std::cout << "out string: " << outString.size() << std::endl;
for(auto&& out : outString)
std::cout << out << std::endl;
auto singleInt = find<int>(temp);
if(singleInt)
std::cout << "first int " << *singleInt << std::endl;
auto singleBool = find<bool>(temp);
if(!singleBool)
std::cout << "ok: bool not found" << std::endl;
}
LIVE DEMO
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With