scope.hpp

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#pragma once
 
/// @file userver/components/scope.hpp
/// @brief @copybrief components::MakeScope
 
#include <functional>
#include <memory>
#include <optional>
 
#include <userver/utils/assert.hpp>
 
USERVER_NAMESPACE_BEGIN
 
namespace components {
 
namespace impl {
class ScopeBase {
public:
    virtual ~ScopeBase() = default;
 
    virtual void AfterConstruction() = 0;
};
 
template <typename Handle>
class Scope final : public ScopeBase {
public:
    using AfterConstructionCallback = std::function<Handle()>;
 
    explicit Scope(AfterConstructionCallback after_construction)
        : after_construction_(std::move(after_construction))
    {}
 
    void AfterConstruction() override { before_destruction_.emplace(after_construction_()); }
 
private:
    AfterConstructionCallback after_construction_;
    std::optional<Handle> before_destruction_;
};
 
template <>
class Scope<void> final : public ScopeBase {
public:
    using AfterConstructionCallback = std::function<void()>;
 
    explicit Scope(AfterConstructionCallback after_construction)
        : after_construction_(std::move(after_construction))
    {}
 
    void AfterConstruction() override { after_construction_(); }
 
private:
    AfterConstructionCallback after_construction_;
};
 
}  // namespace impl
 
/// @brief An object of ScopePtr defines actions to do after
/// a component is constructed and just before it is destroyed.
///
/// @see @ref components::ComponentContext::RegisterScope
using ScopePtr = std::unique_ptr<impl::ScopeBase>;
 
/// @brief Constructs an object of type @ref ScopePtr from
/// a registration callback. The callback must return an object that undoes
/// the registration in its destructor.
///
/// @see @ref components::ComponentContext::RegisterScope
template <typename AfterConstructionCallback>
ScopePtr MakeScope(AfterConstructionCallback after_construction)
{
    using Handle = std::invoke_result_t<AfterConstructionCallback>;
    return std::make_unique<impl::Scope<Handle>>(std::move(after_construction));
}
 
}  // namespace components
 
USERVER_NAMESPACE_END