json-validator/include/jvalidate/detail/on_block_exit.h

#pragma once

#include <concepts>
#include <functional>
#include <utility>

namespace jvalidate::detail {
/**
 * @brief An object representing a cleanup function, to be called as if it was
 * a destructor for the current function scope. Similar to e.g. D-lang's
 * scope(exit) or @see https://en.cppreference.com/w/cpp/experimental/scope_exit
 *
 * Is movable - allowing us to return this scope object from its constructing
 * context into the actual owning context that wants to control that scope.
 */
class OnBlockExit {
private:
  std::function<void()> callback_;

public:
  OnBlockExit() = default;
  template <typename F>
    requires std::constructible_from<std::function<void()>, F>
  explicit(false) OnBlockExit(F && callback) : callback_(std::forward<F>(callback)) {}

  OnBlockExit(OnBlockExit const &) = delete;
  OnBlockExit & operator=(OnBlockExit const &) = delete;

  // Must be explicity implemented because function's move ctor is non-destructive
  OnBlockExit(OnBlockExit && other) noexcept { std::swap(other.callback_, callback_); }

  // Must be explicity implemented because function's move-assign is non-destructive
  OnBlockExit & operator=(OnBlockExit && other) noexcept {
    std::swap(other.callback_, callback_);
    return *this;
  }

  ~OnBlockExit() {
    if (callback_) {
      callback_();
    }
  }
};
}