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Return values instead of assigning to references #154

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Merged
merged 3 commits into from
Feb 15, 2018
Merged

Return values instead of assigning to references #154

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64f911b
Return values instead of assigning to references
zauguin Feb 9, 2018
3a71e95
Make unreachability explicit
zauguin Feb 9, 2018
20c2a4c
Directly initialize tuples
zauguin Feb 12, 2018
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63 changes: 31 additions & 32 deletions hdr/sqlite_modern_cpp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -135,11 +135,15 @@ namespace sqlite {
value_type(database_binder *_binder): _binder(_binder) {};
template<class T>
typename std::enable_if<is_sqlite_value<T>::value, value_type &>::type operator >>(T &result) {
get_col_from_db(_binder->_stmt.get(), next_index++, result);
result = get_col_from_db(_binder->_stmt.get(), next_index++, result_type<T>());
return *this;
}
template<class ...Types>
value_type &operator >>(std::tuple<Types...>& values);
value_type &operator >>(std::tuple<Types...>& values) {
values = handle_tuple<std::tuple<typename std::decay<Types>::type...>>(std::index_sequence_for<Types...>());
next_index += sizeof...(Types);
return *this;
}
template<class ...Types>
value_type &operator >>(std::tuple<Types...>&& values) {
return *this >> values;
Expand All @@ -154,6 +158,14 @@ namespace sqlite {
return sqlite3_column_count(_binder->_stmt.get()) >= next_index;
}
private:
template<class Tuple, std::size_t ...Index>
Tuple handle_tuple(std::index_sequence<Index...>) {
return Tuple(
get_col_from_db(
_binder->_stmt.get(),
next_index + Index,
result_type<typename std::tuple_element<Index, Tuple>::type>())...);
}
database_binder *_binder;
int next_index = 0;
};
Expand Down Expand Up @@ -198,27 +210,6 @@ namespace sqlite {
mutable value_type value{_binder}; // mutable, because `changing` the value is just reading it
};

namespace detail {
template<typename Tuple, int Element = 0, bool Last = (std::tuple_size<Tuple>::value == Element)> struct tuple_iterate {
static void iterate(Tuple& t, row_iterator::value_type& row) {
row >> std::get<Element>(t);
tuple_iterate<Tuple, Element + 1>::iterate(t, row);
}
};

template<typename Tuple, int Element> struct tuple_iterate<Tuple, Element, true> {
static void iterate(Tuple&, row_iterator::value_type&) {}
};
}

template<class ...Types>
row_iterator::value_type &row_iterator::value_type::operator >>(std::tuple<Types...>& values) {
assert(!next_index);
detail::tuple_iterate<std::tuple<Types...>>::iterate(values, *this);
next_index = sizeof...(Types) + 1;
return *this;
}

inline row_iterator database_binder::begin() {
return row_iterator(*this);
}
Expand Down Expand Up @@ -558,16 +549,20 @@ namespace sqlite {
sqlite3_value** vals,
Values&&... values
) {
typename std::remove_cv<
using arg_type = typename std::remove_cv<
typename std::remove_reference<
typename utility::function_traits<
typename Functions::first_type
>::template argument<sizeof...(Values)>
>::type
>::type value{};
get_val_from_db(vals[sizeof...(Values) - 1], value);
>::type;

step<Count, Functions>(db, count, vals, std::forward<Values>(values)..., std::move(value));
step<Count, Functions>(
db,
count,
vals,
std::forward<Values>(values)...,
get_val_from_db(vals[sizeof...(Values) - 1], result_type<arg_type>()));
}

template<
Expand Down Expand Up @@ -618,14 +613,18 @@ namespace sqlite {
sqlite3_value** vals,
Values&&... values
) {
typename std::remove_cv<
using arg_type = typename std::remove_cv<
typename std::remove_reference<
typename utility::function_traits<Function>::template argument<sizeof...(Values)>
>::type
>::type value{};
get_val_from_db(vals[sizeof...(Values)], value);

scalar<Count, Function>(db, count, vals, std::forward<Values>(values)..., std::move(value));
>::type;

scalar<Count, Function>(
db,
count,
vals,
std::forward<Values>(values)...,
get_val_from_db(vals[sizeof...(Values)], result_type<arg_type>()));
}

template<
Expand Down
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