added sqlite query result and enhanced column generator and value extractor

include/matador/sql/query_result.hpp

@@ -1,6 +1,8 @@
 #ifndef QUERY_QUERY_RESULT_HPP
 #define QUERY_QUERY_RESULT_HPP
 
+#include "matador/sql/query_result_impl.hpp"
+
 #include <memory>
 
 namespace matador::sql {
@@ -15,13 +17,17 @@ public:
   using iterator_category = std::forward_iterator_tag;
   using value_type = Type;
   using difference_type = std::ptrdiff_t;
+  using self = query_result_iterator<Type>;  /**< Shortcut for this class. */
   using pointer = value_type*;               /**< Shortcut for the pointer type. */
   using reference = value_type&;             /**< Shortcut for the reference type */
 
 public:
   query_result_iterator() = default;
-  explicit query_result_iterator(query_result<Type> &res, Type *obj = nullptr)
-  : obj_(obj)
+  explicit query_result_iterator(query_result<Type> &res)
+  : result_(res)
+  {}
+  query_result_iterator(query_result<Type> &res, std::unique_ptr<Type> obj)
+  : obj_(std::move(obj))
   , result_(res)
   {}
   query_result_iterator(query_result_iterator&& x) noexcept
@@ -48,19 +54,38 @@ public:
     return obj_ != rhs.obj_;
   }
 
+  self& operator++()
+  {
+    obj_.reset(result_.create());
+    result_.bind(*obj_);
+    if (!result_.fetch(*obj_)) {
+      obj_.reset();
+    }
+
+    return *this;
+  }
+
+  self operator++(int)
+  {
+    const self tmp(result_, obj_);
+
+    obj_.reset(result_.create());
+    result_.bind(*obj_);
+    if (!result_.fetch(*obj_)) {
+      obj_.reset();
+    }
+
+    return std::move(tmp);
+  }
+
   pointer operator->()
   {
     return obj_.get();
   }
 
-  reference operator&()
+  reference operator*()
   {
-    return &obj_.get();
-  }
-
-  std::unique_ptr<Type> operator*()
-  {
-    return std::move(obj_);
+    return *obj_;
   }
 
   pointer get()
@@ -73,7 +98,7 @@ public:
     return obj_.release();
   }
 
-protected:
+private:
   std::unique_ptr<Type> obj_;
   query_result<Type> &result_;
 };
@@ -82,13 +107,32 @@ template < typename Type >
 class query_result
 {
 public:
-  query_result(std::string sql) : sql_(std::move(sql)) {}
+  using iterator = query_result_iterator<Type>;
 
-  [[nodiscard]] const std::string& str() const { return sql_; }
+public:
+  explicit query_result(std::unique_ptr<query_result_impl> impl)
+  : impl_(std::move(impl)) {}
+
+  iterator begin() { return std::move(++iterator(*this)); }
+  iterator end() { return {}; }
 
-  Type begin() { return {}; }
 private:
-  std::string sql_;
+  friend class query_result_iterator<Type>;
+
+  Type* create() { return new Type; }
+
+  void bind(const Type &obj)
+  {
+    impl_->bind(obj);
+  }
+
+  bool fetch(Type &obj)
+  {
+    return impl_->fetch(obj);
+  }
+
+private:
+  std::unique_ptr<query_result_impl> impl_;
 };
 
 }