Use if constexpr to make things a lot more readable

src/database/index.hpp

@@ -8,13 +8,9 @@
 namespace
 {
 template <std::size_t N=0, typename... T>
-typename std::enable_if<N == sizeof...(T), void>::type
+void add_column_name(std::string& out)
-add_column_name(std::string&)
+{
-{ }
+  if constexpr(N < sizeof...(T))
-
-template <std::size_t N=0, typename... T>
-typename std::enable_if<N < sizeof...(T), void>::type
-add_column_name(std::string& out)
     {
       using ColumnType = typename std::remove_reference<decltype(std::get<N>(std::declval<std::tuple<T...>>()))>::type;
       out += ColumnType::name;
@@ -23,6 +19,7 @@ add_column_name(std::string& out)
       add_column_name<N + 1, T...>(out);
     }
 }
+}
 
 template <typename... Columns>
 void create_index(DatabaseEngine& db, const std::string& name, const std::string& table)

src/database/insert_query.hpp

@@ -11,19 +11,16 @@
 #include <tuple>
 
 template <std::size_t N=0, typename... T>
-typename std::enable_if<N < sizeof...(T), void>::type
+void update_autoincrement_id(std::tuple<T...>& columns, Statement& statement)
-update_autoincrement_id(std::tuple<T...>& columns, Statement& statement)
+{
+  if constexpr(N < sizeof...(T))
     {
       using ColumnType = typename std::decay<decltype(std::get<N>(columns))>::type;
       if (std::is_same<ColumnType, Id>::value)
         auto&& column = std::get<Id>(columns);
       update_autoincrement_id<N + 1>(columns, statement);
     }
-
+}
-template <std::size_t N=0, typename... T>
-typename std::enable_if<N == sizeof...(T), void>::type
-update_autoincrement_id(std::tuple<T...>&, Statement&)
-{}
 
 struct InsertQuery: public Query
 {
@@ -53,22 +50,19 @@ struct InsertQuery: public Query
   }
 
   template <int N=0, typename... T>
-  typename std::enable_if<N < sizeof...(T), void>::type
+  void bind_param(const std::tuple<T...>& columns, Statement& statement, int index=1)
-  bind_param(const std::tuple<T...>& columns, Statement& statement, int index=1)
+  {
+    if constexpr(N < sizeof...(T))
       {
         auto&& column = std::get<N>(columns);
         using ColumnType = std::decay_t<decltype(column)>;
 
-    if (!std::is_same<ColumnType, Id>::value)
+        if constexpr(!std::is_same<ColumnType, Id>::value)
           actual_bind(statement, column.value, index++);
 
         this->bind_param<N + 1>(columns, statement, index);
       }
-
+  }
-  template <int N=0, typename... T>
-  typename std::enable_if<N == sizeof...(T), void>::type
-  bind_param(const std::tuple<T...>&, Statement&, int)
-  {}
 
   template <typename... T>
   void insert_values(const std::tuple<T...>& columns)
@@ -79,8 +73,9 @@ struct InsertQuery: public Query
   }
 
   template <int N=0, typename... T>
-  typename std::enable_if<N < sizeof...(T), void>::type
+  void insert_value(const std::tuple<T...>& columns, int index=1)
-  insert_value(const std::tuple<T...>& columns, int index=1)
+  {
+    if constexpr(N < sizeof...(T))
       {
         using ColumnType = std::decay_t<decltype(std::get<N>(columns))>;
 
@@ -92,10 +87,7 @@ struct InsertQuery: public Query
           }
         this->insert_value<N + 1>(columns, index);
       }
-  template <int N=0, typename... T>
+  }
-  typename std::enable_if<N == sizeof...(T), void>::type
-  insert_value(const std::tuple<T...>&, const int)
-  { }
 
   template <typename... T>
   void insert_col_names(const std::tuple<T...>& columns)
@@ -106,8 +98,9 @@ struct InsertQuery: public Query
   }
 
   template <int N=0, typename... T>
-  typename std::enable_if<N < sizeof...(T), void>::type
+  void insert_col_name(const std::tuple<T...>& columns)
-  insert_col_name(const std::tuple<T...>& columns)
+  {
+    if constexpr(N < sizeof...(T))
       {
         using ColumnType = std::decay_t<decltype(std::get<N>(columns))>;
 
@@ -121,9 +114,5 @@ struct InsertQuery: public Query
 
         this->insert_col_name<N + 1>(columns);
       }
-
+  }
-  template <int N=0, typename... T>
-  typename std::enable_if<N == sizeof...(T), void>::type
-  insert_col_name(const std::tuple<T...>&)
-  {}
 };

src/database/query.hpp

@@ -13,12 +13,12 @@
 
 void actual_bind(Statement& statement, const std::string& value, int index);
 void actual_bind(Statement& statement, const std::int64_t& value, int index);
-template <typename T, typename std::enable_if_t<std::is_integral<T>::value>* = 0>
+void actual_bind(Statement& statement, const std::optional<bool>& value, int index);
+template <typename T>
 void actual_bind(Statement& statement, const T& value, int index)
 {
   actual_bind(statement, static_cast<std::int64_t>(value), index);
 }
-void actual_bind(Statement& statement, const std::optional<bool>& value, int index);
 
 #ifdef DEBUG_SQL_QUERIES
 #include <utils/scopetimer.hpp>
@@ -57,38 +57,27 @@ struct Query
 #endif
 };
 
-template <typename ColumnType>
+void actual_add_param(Query& query, const std::string& val);
-void add_param(Query& query, const ColumnType& column)
+void actual_add_param(Query& query, const std::optional<bool>& val);
-{
-  std::cout << "add_param<ColumnType>" << std::endl;
-  actual_add_param(query, column.value);
-}
-
 template <typename T>
 void actual_add_param(Query& query, const T& val)
 {
   query.params.push_back(std::to_string(val));
 }
 
-void actual_add_param(Query& query, const std::string& val);
-
-template <typename T>
-typename std::enable_if<!std::is_integral<T>::value, Query&>::type
-operator<<(Query& query, const T&)
-{
-  query.body += T::name;
-  return query;
-}
-void actual_add_param(Query& query, const std::optional<bool>& val);
-
 Query& operator<<(Query& query, const char* str);
 Query& operator<<(Query& query, const std::string& str);
-template <typename Integer>
+template <typename T>
-typename std::enable_if<std::is_integral<Integer>::value, Query&>::type
+Query& operator<<(Query& query, const T& i)
-operator<<(Query& query, const Integer& i)
+{
+  if constexpr(std::is_integral<T>::value)
     {
       query.body += "$" + std::to_string(query.current_param++);
       actual_add_param(query, i);
+    }
+  else
+    {
+      query.body += T::name;
+    }
   return query;
 }
-

src/database/row.hpp

@@ -29,14 +29,9 @@ struct Row
     return col.value;
   }
 
-  template <bool Coucou=true>
+  void save(std::unique_ptr<DatabaseEngine>& db)
-  void save(std::unique_ptr<DatabaseEngine>& db, typename std::enable_if<!is_one_of<Id, T...> && Coucou>::type* = nullptr)
   {
-    this->insert(*db);
+    if constexpr(is_one_of<Id, T...>)
-  }
-
-  template <bool Coucou=true>
-  void save(std::unique_ptr<DatabaseEngine>& db, typename std::enable_if<is_one_of<Id, T...> && Coucou>::type* = nullptr)
       {
         const Id& id = std::get<Id>(this->columns);
         if (id.value == Id::unset_value)
@@ -48,23 +43,26 @@ struct Row
         else
           this->update(*db);
       }
+    else
+      this->insert(*db);
+  }
 
  private:
-  template <bool Coucou=true>
+  void insert(DatabaseEngine& db)
-  void insert(DatabaseEngine& db, typename std::enable_if<is_one_of<Id, T...> && Coucou>::type* = nullptr)
+  {
+    if constexpr(is_one_of<Id, T...>)
       {
         InsertQuery query(this->table_name, this->columns);
         // Ugly workaround for non portable stuff
         query.body += db.get_returning_id_sql_string(Id::name);
         query.execute(db, this->columns);
       }
-
+    else
-  template <bool Coucou=true>
-  void insert(DatabaseEngine& db, typename std::enable_if<!is_one_of<Id, T...> && Coucou>::type* = nullptr)
       {
         InsertQuery query(this->table_name, this->columns);
         query.execute(db, this->columns);
       }
+  }
 
   void update(DatabaseEngine& db)
   {

src/database/select_query.hpp

@@ -15,34 +15,27 @@
 using namespace std::string_literals;
 
 template <typename T>
-typename std::enable_if<std::is_integral<T>::value, std::int64_t>::type
+auto extract_row_value(Statement& statement, const int i)
-extract_row_value(Statement& statement, const int i)
 {
+  if constexpr(std::is_integral<T>::value)
     return statement.get_column_int64(i);
-}
+  else if constexpr (std::is_same<std::string, T>::value)
-
-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);
-}
+  else if (std::is_same<std::optional<bool>, T>::value)
-
-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;
+        return std::optional<bool>{true};
       else if (integer < 0)
-    return false;
+        return std::optional<bool>{false};
-  return std::nullopt;
+      return std::optional<bool>{};
+    }
 }
 
 template <std::size_t N=0, typename... T>
-typename std::enable_if<N < sizeof...(T), void>::type
+void extract_row_values(Row<T...>& row, Statement& statement)
-extract_row_values(Row<T...>& row, Statement& statement)
+{
+  if constexpr(N < sizeof...(T))
     {
       using ColumnType = typename std::remove_reference<decltype(std::get<N>(row.columns))>::type;
 
@@ -51,11 +44,7 @@ extract_row_values(Row<T...>& row, Statement& 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
@@ -69,8 +58,9 @@ struct SelectQuery: public Query
     }
 
     template <std::size_t N=0>
-    typename std::enable_if<N < sizeof...(T), void>::type
+    void insert_col_name()
-    insert_col_name()
+    {
+      if constexpr(N < sizeof...(T))
         {
           using ColumnsType = std::tuple<T...>;
           using ColumnType = typename std::remove_reference<decltype(std::get<N>(std::declval<ColumnsType>()))>::type;
@@ -82,10 +72,7 @@ struct SelectQuery: public Query
 
           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()
     {

src/database/table.hpp

@@ -93,22 +93,21 @@ class Table
  private:
 
   template <std::size_t N=0>
-  typename std::enable_if<N < sizeof...(T), void>::type
+  void add_column_if_not_exists(DatabaseEngine& db, const std::set<std::string>& existing_columns)
-  add_column_if_not_exists(DatabaseEngine& db, const std::set<std::string>& existing_columns)
+  {
+    if constexpr(N < sizeof...(T))
       {
         using ColumnType = typename std::remove_reference<decltype(std::get<N>(std::declval<ColumnTypes>()))>::type;
         if (existing_columns.count(ColumnType::name) == 0)
           add_column_to_table<ColumnType>(db, this->name);
         add_column_if_not_exists<N + 1>(db, existing_columns);
       }
-  template <std::size_t N=0>
+  }
-  typename std::enable_if<N == sizeof...(T), void>::type
-  add_column_if_not_exists(DatabaseEngine&, const std::set<std::string>&)
-  {}
 
   template <std::size_t N=0>
-  typename std::enable_if<N < sizeof...(T), void>::type
+  void add_column_create(DatabaseEngine& db, std::string& str)
-  add_column_create(DatabaseEngine& db, std::string& str)
+  {
+    if constexpr(N < sizeof...(T))
       {
         using ColumnType = typename std::remove_reference<decltype(std::get<N>(std::declval<ColumnTypes>()))>::type;
         str += ColumnType::name;
@@ -119,10 +118,7 @@ class Table
 
         add_column_create<N + 1>(db, str);
       }
-  template <std::size_t N=0>
+  }
-  typename std::enable_if<N == sizeof...(T), void>::type
-  add_column_create(DatabaseEngine&, std::string&)
-  { }
 
   const std::string name;
 };

src/database/update_query.hpp

@@ -39,14 +39,16 @@ struct UpdateQuery: public Query
   }
 
   template <int N=0, typename... T>
-  typename std::enable_if<N < sizeof...(T), void>::type
+  void insert_col_name_and_value(const std::tuple<T...>& columns)
-  insert_col_name_and_value(const std::tuple<T...>& columns)
+  {
+    if constexpr(N < sizeof...(T))
       {
         using ColumnType = std::decay_t<decltype(std::get<N>(columns))>;
 
         if (!std::is_same<ColumnType, Id>::value)
           {
-        this->body += ColumnType::name + "=$"s + std::to_string(this->current_param);
+            this->body += ColumnType::name + "=$"s
+                          + std::to_string(this->current_param);
             this->current_param++;
 
             if (N < (sizeof...(T) - 1))
@@ -55,11 +57,7 @@ struct UpdateQuery: public Query
 
         this->insert_col_name_and_value<N + 1>(columns);
       }
-  template <int N=0, typename... T>
+  }
-  typename std::enable_if<N == sizeof...(T), void>::type
-  insert_col_name_and_value(const std::tuple<T...>&)
-  {}
-
 
   template <typename... T>
   void execute(DatabaseEngine& db, const std::tuple<T...>& columns)
@@ -76,8 +74,9 @@ struct UpdateQuery: public Query
   }
 
   template <int N=0, typename... T>
-  typename std::enable_if<N < sizeof...(T), void>::type
+  void bind_param(const std::tuple<T...>& columns, Statement& statement, int index=1)
-  bind_param(const std::tuple<T...>& columns, Statement& statement, int index=1)
+  {
+    if constexpr(N < sizeof...(T))
       {
         auto&& column = std::get<N>(columns);
         using ColumnType = std::decay_t<decltype(column)>;
@@ -87,11 +86,7 @@ struct UpdateQuery: public Query
 
         this->bind_param<N + 1>(columns, statement, index);
       }
-
+  }
-  template <int N=0, typename... T>
-  typename std::enable_if<N == sizeof...(T), void>::type
-  bind_param(const std::tuple<T...>&, Statement&, int)
-  {}
 
   template <typename... T>
   void bind_id(const std::tuple<T...>& columns, Statement& statement)