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Add a proxy class to return from operator[]

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This commit is contained in:
King_DuckZ 2020-04-13 14:36:41 +02:00
parent f462562ab7
commit ff0737f567
4 changed files with 61 additions and 6 deletions
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17
src/env_base.cpp
View file

@ -16,9 +16,26 @@
*/
#include "env_base.hpp"
#include "string_view_cat.hpp"
namespace duck {
bool EnvBase::empty() const noexcept {
return 0 == this->size();
}
std::string_view EnvBase::operator[] (std::string_view name) const noexcept {
return this->get(name, "");
}
detail::EnvVarProxy<std::string_view> EnvBase::operator[] (std::string_view name) noexcept {
return {name, this};
}
detail::EnvVarProxy<std::string> EnvBase::operator[] (std::string&& name) noexcept {
return {std::move(name), this};
}
detail::EnvVarProxy<std::string> EnvBase::operator[] (const std::string& name) noexcept {
return {to_string(name), this};
}
} //namespace duck

45
src/env_base.hpp
View file

@ -22,6 +22,23 @@
#include <utility>
namespace duck {
class EnvBase;
namespace detail {
template <typename S>
class EnvVarProxy {
public:
template <typename S1>
EnvVarProxy (S1&& name, EnvBase* env) noexcept;
EnvVarProxy& operator= (std::string_view new_val);
operator std::string_view() const noexcept;
private:
S m_name;
EnvBase* m_env;
};
} //namespace detail
class EnvBase {
public:
typedef std::string_view mapped_type;
@ -33,7 +50,11 @@ namespace duck {
EnvBase() = default;
virtual ~EnvBase() noexcept = default;
virtual std::string_view operator[] (std::string_view name) const noexcept = 0;
std::string_view operator[] (std::string_view name) const noexcept;
detail::EnvVarProxy<std::string_view> operator[] (std::string_view name) noexcept;
detail::EnvVarProxy<std::string> operator[] (std::string&& name) noexcept;
detail::EnvVarProxy<std::string> operator[] (const std::string& name) noexcept;
virtual std::optional<std::string_view> get (std::string_view name) const noexcept = 0;
virtual std::string_view get (std::string_view name, std::string_view def) const noexcept = 0;
virtual void set (std::string_view name, std::string_view value) = 0;
@ -43,4 +64,26 @@ namespace duck {
virtual bool empty() const noexcept;
virtual void clear() noexcept = 0;
};
namespace detail {
template <typename S>
template <typename S1>
inline EnvVarProxy<S>::EnvVarProxy (S1&& name, EnvBase* env) noexcept :
m_name(std::forward<S1>(name)),
m_env(env)
{
}
template <typename S>
inline auto EnvVarProxy<S>::operator= (std::string_view new_val) -> EnvVarProxy& {
m_env->set(m_name, new_val);
return *this;
}
template <typename S>
inline EnvVarProxy<S>::operator std::string_view() const noexcept {
return (*m_env)[m_name];
}
} //namespace detail
} //namespace duck

4
src/env_real.cpp
View file

@ -165,10 +165,6 @@ EnvReal::EnvReal() :
{
}
std::string_view EnvReal::operator[] (std::string_view name) const noexcept {
return this->get(name, "");
}
std::optional<std::string_view> EnvReal::get (std::string_view name) const noexcept {
const char* const ret = this->raw_fetch_env(name);
if (ret)

1
src/env_real.hpp
View file

@ -26,7 +26,6 @@ namespace duck {
EnvReal();
virtual ~EnvReal() noexcept = default;
virtual std::string_view operator[] (std::string_view name) const noexcept override;
virtual std::optional<std::string_view> get (std::string_view name) const noexcept override;
virtual std::string_view get (std::string_view name, std::string_view def) const noexcept override;
virtual void set (std::string_view name, std::string_view value) override;