From f01a644dc040ca37f7d3c3ac96bd353b5fbccf52 Mon Sep 17 00:00:00 2001
From: dend <dend456@gmail.com>
Date: Sun, 12 Feb 2017 22:10:29 -0500
Subject: [PATCH] Added convenience functions for constructing objects from a
 row

---
 include/SQLiteCpp/Column.h    | 17 +++++++++++
 include/SQLiteCpp/Statement.h | 34 +++++++++++++++++++++
 tests/Statement_test.cpp      | 57 +++++++++++++++++++++++++++++++++++
 3 files changed, 108 insertions(+)

diff --git a/include/SQLiteCpp/Column.h b/include/SQLiteCpp/Column.h
index cfafa079..be0babc4 100644
--- a/include/SQLiteCpp/Column.h
+++ b/include/SQLiteCpp/Column.h
@@ -260,5 +260,22 @@ class Column
  */
 std::ostream& operator<<(std::ostream& aStream, const Column& aColumn);
 
+#if __cplusplus >= 201402L || (defined(_MSC_VER) && _MSC_VER >= 1900)
+    // Create an instance of T from the first N columns, see declaration in Statement.h for full details
+    template<typename T, int N>
+    T Statement::getColumns()
+    {
+        checkRow();
+        checkIndex(N - 1);
+        return getColumns<T>(std::make_integer_sequence<int, N>{});
+    }
+
+    // Helper function called by getColums<typename T, int N>
+    template<typename T, const int... Is>
+    T Statement::getColumns(const std::integer_sequence<int, Is...>)
+    {
+        return T(Column(mStmtPtr, Is)...);
+    }
+#endif
 
 }  // namespace SQLite
diff --git a/include/SQLiteCpp/Statement.h b/include/SQLiteCpp/Statement.h
index 594ee38c..6d1d3191 100644
--- a/include/SQLiteCpp/Statement.h
+++ b/include/SQLiteCpp/Statement.h
@@ -427,6 +427,40 @@ class Statement
      */
     Column  getColumn(const char* apName);
 
+#if __cplusplus >= 201402L || (defined(_MSC_VER) && _MSC_VER >= 1900)
+     /**
+     * @brief Return an instance of T constructed from copies of the first N columns
+     *
+     *  Can be used to access the data of the current row of result when applicable,
+     * while the executeStep() method returns true.
+     *
+     *  Throw an exception if there is no row to return a Column from:
+     * - if provided column count is out of bound
+     * - before any executeStep() call
+     * - after the last executeStep() returned false
+     * - after a reset() call
+     *
+     *  Throw an exception if the specified column count is out of the [0, getColumnCount()) range.
+     *
+     * @tparam  T   Object type to construct
+     * @tparam  N   Number of columns
+     *
+     * @note Requires std=C++14
+     */
+    template<typename T, int N>
+    T       getColumns();
+
+private:
+    /**
+    * @brief Helper function used by getColumns<typename T, int N> to expand an integer_sequence used to generate
+    *        the required Column objects
+    */
+    template<typename T, const int... Is>
+    T       getColumns(const std::integer_sequence<int, Is...>);
+
+public:
+#endif
+
     /**
      * @brief Test if the column value is NULL
      *
diff --git a/tests/Statement_test.cpp b/tests/Statement_test.cpp
index 7f38b6bb..8bd626c2 100644
--- a/tests/Statement_test.cpp
+++ b/tests/Statement_test.cpp
@@ -651,3 +651,60 @@ TEST(Statement, getName) {
     EXPECT_EQ("msg", oname1);
 #endif
 }
+
+#if __cplusplus >= 201402L || (defined(_MSC_VER) && _MSC_VER >= 1900)
+TEST(Statement, getColumns) {
+    struct GetRowTestStruct
+    {
+        int id;
+        std::string msg;
+        int integer;
+        double real;
+        GetRowTestStruct(int _id, std::string _msg, int _integer, double _real)
+        : id(_id), msg(_msg), integer(_integer), real(_real)
+        {}
+
+        GetRowTestStruct(int _id, const std::string& _msg)
+        : id(_id), msg(_msg), integer(-1), real(0.0)
+        {}
+    };
+
+    // Create a new database
+    SQLite::Database db(":memory:", SQLite::OPEN_READWRITE | SQLite::OPEN_CREATE);
+    EXPECT_EQ(SQLite::OK, db.getErrorCode());
+    EXPECT_EQ(SQLite::OK, db.getExtendedErrorCode());
+
+    // Create a new table
+    EXPECT_EQ(0, db.exec("CREATE TABLE test (id INTEGER PRIMARY KEY, msg TEXT, int INTEGER, double REAL)"));
+    EXPECT_EQ(SQLite::OK, db.getErrorCode());
+    EXPECT_EQ(SQLite::OK, db.getExtendedErrorCode());
+
+    // Create a first row
+    EXPECT_EQ(1, db.exec("INSERT INTO test VALUES (NULL, \"first\", 123, 0.123)"));
+    EXPECT_EQ(1, db.getLastInsertRowid());
+    EXPECT_EQ(1, db.getTotalChanges());
+
+    // Compile a SQL query
+    SQLite::Statement query(db, "SELECT * FROM test");
+    EXPECT_STREQ("SELECT * FROM test", query.getQuery().c_str());
+    EXPECT_EQ(4, query.getColumnCount());
+    query.executeStep();
+    EXPECT_TRUE(query.isOk());
+    EXPECT_FALSE(query.isDone());
+
+    // Get all columns
+    auto testStruct = query.getColumns<GetRowTestStruct, 4>();
+    EXPECT_EQ(1, testStruct.id);
+    EXPECT_EQ("first", testStruct.msg);
+    EXPECT_EQ(123, testStruct.integer);
+    EXPECT_EQ(0.123, testStruct.real);
+    
+    // Get only the first 2 columns
+    auto testStruct2 = query.getColumns<GetRowTestStruct, 2>();
+    EXPECT_EQ(1, testStruct2.id);
+    EXPECT_EQ("first", testStruct2.msg);
+    EXPECT_EQ(-1, testStruct2.integer);
+    EXPECT_EQ(0.0, testStruct2.real);
+}
+#endif
+