use result chaining in demo::main.cpp

demo/main.cpp

@@ -156,16 +156,19 @@ QUERY_HELPER( temporary_table, id );
 int main() {
     using namespace matador::sql;
     using namespace matador::object;
+    using namespace matador::utils;
 
     const std::string env_var{"MATADOR_BACKENDS_PATH"};
 
     std::string dns{"sqlite://demo.db"};
     schema s( "main" );
-    s.attach<author>( "authors" );
-    s.attach<book>( "books" );
+    auto result = s.attach<author>( "authors" ).and_then( [&s] {
+        return s.attach<book>( "books" );
+    } );
+    // s.attach<book>( "books" );
 
     connection c( dns );
-    auto result = c.open();
+    result = c.open();
     // s.create( c );
     //
     // auto create_authors_sql = c.query( s )