From 8c483aa805eb3da25be685ee875555662cab1038 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?louiz=E2=80=99?= <louiz@louiz.org>
Date: Sat, 17 Mar 2018 17:33:29 +0100
Subject: Re-apply "Use if constexpr to make things a lot more readable"

This reverts commit d0e3c71b91f1a1c1780158789fd42b8ac7209495.
---
 src/database/select_query.hpp | 77 ++++++++++++++++++-------------------------
 1 file changed, 32 insertions(+), 45 deletions(-)

(limited to 'src/database/select_query.hpp')

diff --git a/src/database/select_query.hpp b/src/database/select_query.hpp
index cd9943c..f7496a4 100644
--- a/src/database/select_query.hpp
+++ b/src/database/select_query.hpp
@@ -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()
     {
-- 
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