added field class

include/matador/sql/field.hpp

@@ -4,40 +4,107 @@
 #include "matador/sql/any_type.hpp"
 #include "matador/sql/any_type_to_visitor.hpp"
 
+#include "matador/utils/types.hpp"
+
+#include <optional>
 #include <string>
 
 namespace matador::sql {
 
+enum class field_type {
+  Integer,
+  FloatingPoint,
+  String,
+  Boolean,
+  Blob,
+  Null
+};
+
+template < typename Type, typename Enable = void >
+struct field_traits;
+
+template<typename Type>
+struct field_traits<Type, typename std::enable_if<std::is_integral<Type>::value && !std::is_same<Type, bool>::value>::type>
+{
+  static field_type type() { return field_type::Integer; }
+};
+
+template<typename Type>
+struct field_traits<Type, typename std::enable_if<std::is_floating_point<Type>::value>::type>
+{
+  static field_type type() { return field_type::FloatingPoint; }
+};
+
+template<typename Type>
+struct field_traits<Type, typename std::enable_if<std::is_same<Type, std::string>::value>::type>
+{
+  static field_type type() { return field_type::String; }
+};
+
+template<typename Type>
+struct field_traits<Type, typename std::enable_if<std::is_same<Type, bool>::value>::type>
+{
+  static field_type type() { return field_type::Boolean; }
+};
+
+template<typename Type>
+struct field_traits<Type, typename std::enable_if<std::is_same<Type, nullptr_t>::value>::type>
+{
+  static field_type type() { return field_type::Null; }
+};
+
+template<typename Type>
+struct field_traits<Type, typename std::enable_if<std::is_same<Type, utils::blob>::value>::type>
+{
+  static field_type type() { return field_type::Blob; }
+};
+
 class field
 {
 public:
+  explicit field(std::string name);
+  template<typename Type>
+  field(std::string name, Type value)
+  : name_(std::move(name))
+  , value_(value)
+  , type_(field_traits<Type>::type()) {}
+  field(const field &x) = default;
+  field& operator=(const field &x) = default;
+  field(field &&x) noexcept;
+  field& operator=(field &&x) noexcept;
+
+  template<typename Type>
+  field& operator=(Type value) {
+    value_ = std::move(value);
+    type_ = field_traits<Type>::type();
+    return *this;
+  }
 
   [[nodiscard]] const std::string& name() const;
 
   template<class Type>
-  Type as() const
+  std::optional<Type> as() const
   {
-    const Type* ptr= std::get_if<Type>(&value_);
-    if (ptr) {
-      return *ptr;
-    }
     any_type_to_visitor<Type> visitor;
     std::visit(visitor, const_cast<any_type&>(value_));
     return visitor.result;
   }
 
-  bool is_integer() const;
-  bool is_floating_point() const;
-  bool is_bool() const;
-  bool is_string() const;
-  bool is_blob() const;
-  bool is_null() const;
+  [[nodiscard]] std::string str() const;
+
+  [[nodiscard]] bool is_integer() const;
+  [[nodiscard]] bool is_floating_point() const;
+  [[nodiscard]] bool is_bool() const;
+  [[nodiscard]] bool is_string() const;
+  [[nodiscard]] bool is_blob() const;
+  [[nodiscard]] bool is_null() const;
 
   friend std::ostream& operator<<(std::ostream &out, const field &col);
 
 private:
   std::string name_;
   any_type value_;
+  field_type type_;
 };
 
 }