C++ type erasure

erased.cpp

#pragma once

/**
 * Concept enforcing values on the templated types. Clients are not exposed to this.
 */
template <typename T>
concept ToBeErased = requires(T a) {
  { a.doSomething() } -> std::convertible_to<void>;
};

/**
 * Type-erased wrapper over templated types.
 */
class Erased {
 public:
  /**
   * Erase the type of a concrete template instance.
   */
  template <ToBeErased T>
  explicit Wrapper(T obj)
      : impl_(std::make_unique<Model<T>>(std::move(obj))) {}

  /**
   * Invoke a function on the templated instance.
   */
  void doSomething() {
    obj_->doSomething();
  }

 private:
  struct Interface {
    virtual ~Interface() = default;
    virtual void DoSomething() = 0;
  };

  template <typename T>
  struct Model final : Interface {
    Model(T obj)
        : obj_(std::move(obj)) {}

    void doSomething() override {
      obj_.doSomething();
    }

    T obj_;
  };

  std::unique_ptr<Interface> obj_;
};