Storing std::any in a Container

You can store std::any objects in a container just like you would any other type. Here's an example with std::vector:

1#include <any>
2#include <iostream>
3#include <string>
4#include <vector>
5
6int main() {
7  std::vector<std::any> vec;
8
9  vec.push_back(42);
10  vec.push_back("Hello");
11  vec.push_back(3.14);
12
13  for (const auto& item : vec) {
14    if (item.type() == typeid(int)) {
15      std::cout << "int: " << std::any_cast<
16        int>(item) << '\n';
17    } else if (item.type() == typeid(const char*)) {
18      std::cout << "string: " << std::any_cast<
19        const char*>(item) << '\n';
20    } else if (item.type() == typeid(double)) {
21      std::cout << "double: " << std::any_cast<
22        double>(item) << '\n';
23    }
24  }
25}

1Copy codeint: 42
2string: Hello
3double: 3.14

However, there are a few things to keep in mind:

1. The std::any objects in the container can hold different types, so you need to use std::any_cast with the correct type to access the value. Getting this wrong will throw a std::bad_any_cast exception.
2. Checking the type and casting for each element can be cumbersome and inefficient if done frequently. If your use case allows it, consider using a std::variant or a container of a base class type instead.
3. Copying std::any objects can be expensive, especially if they hold large objects. You might consider using std::unique_ptrstd::any in the container to avoid unnecessary copies, at the cost of more complex memory management.
4. The type-erasure used by std::any has a runtime cost. If performance is critical, consider alternatives like templates or a custom type-erasure implementation tailored to your specific use case.