OptionalDelegatedParameter.h

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#ifndef fhiclcpp_types_OptionalDelegatedParameter_h
#define fhiclcpp_types_OptionalDelegatedParameter_h

#include "fhiclcpp/ParameterSet.h"
#include "fhiclcpp/types/Comment.h"
#include "fhiclcpp/types/Name.h"
#include "fhiclcpp/types/detail/DelegateBase.h"
#include "fhiclcpp/types/detail/ParameterArgumentTypes.h"
#include "fhiclcpp/types/detail/TableMemberRegistry.h"
#include "fhiclcpp/types/detail/strip_containing_names.h"

#include <functional>
#include <optional>

namespace fhicl {

  //========================================================
  class OptionalDelegatedParameter final
    : public detail::DelegateBase,
      private detail::RegisterIfTableMember {
  public:
    explicit OptionalDelegatedParameter(Name&& name);
    explicit OptionalDelegatedParameter(Name&& name, Comment&& comment);
    explicit OptionalDelegatedParameter(Name&& name,
                                        Comment&& comment,
                                        std::function<bool()> maybeUse);
    bool
    hasValue() const
    {
      return pset_ &&
             pset_->has_key(detail::strip_first_containing_name(key()));
    }

    template <typename T>
    std::optional<T>
    get_if_present() const
    {
      if (not pset_) {
        return std::nullopt;
      }

      auto const trimmed_key = detail::strip_first_containing_name(key());
      return pset_->get_if_present<T>(trimmed_key);
    }

    // Obsolete interface
    template <typename T>
    bool
    get_if_present(T& t) const
    {
      if (auto result = get_if_present<T>()) {
        t = *result;
        return true;
      }
      return false;
    }

  private:
    void
    do_set_value(fhicl::ParameterSet const& pset) override
    {
      pset_ = std::make_optional(pset);
    };

    std::optional<ParameterSet> pset_{std::nullopt};
  };
}

#endif /* fhiclcpp_types_OptionalDelegatedParameter_h */

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// mode: c++
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