implemented sqlite fetch

include/matador/sql/query_result.hpp

@@ -1,6 +1,8 @@
 #ifndef QUERY_QUERY_RESULT_HPP
 #define QUERY_QUERY_RESULT_HPP
 
+#include <functional>
+
 #include "matador/sql/query_result_impl.hpp"
 
 #include <memory>
@@ -23,10 +25,10 @@ public:
 
 public:
   query_result_iterator() = default;
-  explicit query_result_iterator(query_result<Type> &res)
+  explicit query_result_iterator(query_result<Type> *res)
   : result_(res)
   {}
-  query_result_iterator(query_result<Type> &res, std::unique_ptr<Type> obj)
+  query_result_iterator(query_result<Type> *res, std::unique_ptr<Type> obj)
   : obj_(std::move(obj))
   , result_(res)
   {}
@@ -56,9 +58,9 @@ public:
 
   self& operator++()
   {
-    obj_.reset(result_.create());
-    result_.bind(*obj_);
-    if (!result_.fetch(*obj_)) {
+    obj_.reset(result_->create());
+    result_->bind(*obj_);
+    if (!result_->fetch(*obj_)) {
       obj_.reset();
     }
 
@@ -69,9 +71,9 @@ public:
   {
     const self tmp(result_, obj_);
 
-    obj_.reset(result_.create());
-    result_.bind(*obj_);
-    if (!result_.fetch(*obj_)) {
+    obj_.reset(result_->create());
+    result_->bind(*obj_);
+    if (!result_->fetch(*obj_)) {
       obj_.reset();
     }
 
@@ -100,7 +102,7 @@ public:
 
 private:
   std::unique_ptr<Type> obj_;
-  query_result<Type> &result_;
+  query_result<Type> *result_{nullptr};
 };
 
 template < typename Type >
@@ -108,18 +110,22 @@ class query_result
 {
 public:
   using iterator = query_result_iterator<Type>;
+  using creator_func = std::function<Type*()>;
 
 public:
   explicit query_result(std::unique_ptr<query_result_impl> impl)
   : impl_(std::move(impl)) {}
+  query_result(std::unique_ptr<query_result_impl> impl, creator_func creator)
+  : creator_(creator)
+  , impl_(std::move(impl)) {}
 
-  iterator begin() { return std::move(++iterator(*this)); }
+  iterator begin() { return std::move(++iterator(this)); }
   iterator end() { return {}; }
 
 private:
   friend class query_result_iterator<Type>;
 
-  Type* create() { return new Type; }
+  Type* create() { return creator_(); }
 
   void bind(const Type &obj)
   {
@@ -132,6 +138,7 @@ private:
   }
 
 private:
+  creator_func creator_ = []{ return new Type; };
   std::unique_ptr<query_result_impl> impl_;
 };