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Use if constexpr to make things a lot more readable

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This commit is contained in:
louiz’
2018-03-16 01:13:50 +01:00
parent ba879a882e
commit d62ca9f879
7 changed files with 163 additions and 212 deletions
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src/database/select_query.hpp
+32 -45
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@@ -15,48 +15,37 @@
using namespace std::string_literals;
template <typename T>
typename std::enable_if<std::is_integral<T>::value, std::int64_t>::type
extract_row_value(Statement& statement, const int i)
auto extract_row_value(Statement& statement, const int i)
{
return statement.get_column_int64(i);
}
template <typename T>
typename std::enable_if<std::is_same<std::string, T>::value, T>::type
extract_row_value(Statement& statement, const int i)
{
return statement.get_column_text(i);
}
template <typename T>
typename std::enable_if<std::is_same<std::optional<bool>, T>::value, T>::type
extract_row_value(Statement& statement, const int i)
{
const auto integer = statement.get_column_int(i);
if (integer > 0)
return true;
else if (integer < 0)
return false;
return std::nullopt;
if constexpr(std::is_integral<T>::value)
return statement.get_column_int64(i);
else if constexpr (std::is_same<std::string, T>::value)
return statement.get_column_text(i);
else if (std::is_same<std::optional<bool>, T>::value)
{
const auto integer = statement.get_column_int(i);
if (integer > 0)
return std::optional<bool>{true};
else if (integer < 0)
return std::optional<bool>{false};
return std::optional<bool>{};
}
}
template <std::size_t N=0, typename... T>
typename std::enable_if<N < sizeof...(T), void>::type
extract_row_values(Row<T...>& row, Statement& statement)
void extract_row_values(Row<T...>& row, Statement& statement)
{
using ColumnType = typename std::remove_reference<decltype(std::get<N>(row.columns))>::type;
if constexpr(N < sizeof...(T))
{
using ColumnType = typename std::remove_reference<decltype(std::get<N>(row.columns))>::type;
auto&& column = std::get<N>(row.columns);
column.value = static_cast<decltype(column.value)>(extract_row_value<typename ColumnType::real_type>(statement, N));
auto&& column = std::get<N>(row.columns);
column.value = static_cast<decltype(column.value)>(extract_row_value<typename ColumnType::real_type>(statement, N));
extract_row_values<N+1>(row, statement);
extract_row_values<N + 1>(row, statement);
}
}
template <std::size_t N=0, typename... T>
typename std::enable_if<N == sizeof...(T), void>::type
extract_row_values(Row<T...>&, Statement&)
{}
template <typename... T>
struct SelectQuery: public Query
{
@@ -69,23 +58,21 @@ struct SelectQuery: public Query
}
template <std::size_t N=0>
typename std::enable_if<N < sizeof...(T), void>::type
insert_col_name()
void insert_col_name()
{
using ColumnsType = std::tuple<T...>;
using ColumnType = typename std::remove_reference<decltype(std::get<N>(std::declval<ColumnsType>()))>::type;
if constexpr(N < sizeof...(T))
{
using ColumnsType = std::tuple<T...>;
using ColumnType = typename std::remove_reference<decltype(std::get<N>(std::declval<ColumnsType>()))>::type;
this->body += " " + std::string{ColumnType::name};
this->body += " " + std::string{ColumnType::name};
if (N < (sizeof...(T) - 1))
this->body += ", ";
if (N < (sizeof...(T) - 1))
this->body += ", ";
this->insert_col_name<N+1>();
this->insert_col_name<N + 1>();
}
}
template <std::size_t N=0>
typename std::enable_if<N == sizeof...(T), void>::type
insert_col_name()
{}
SelectQuery& where()
{