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 )

include/matador/object/schema.hpp

@@ -24,7 +24,7 @@ public:
   explicit schema( const std::string& name = "");
 
   template <typename Type>
-  utils::result<void, utils::error> attach(const std::string name, const std::string &parent = "") {
+  [[nodiscard]] utils::result<void, utils::error> attach(const std::string name, const std::string &parent = "") {
     auto node = schema_node::make_node<Type>(*this, name);
 
     auto result = attach_node(node, parent);
@@ -36,7 +36,7 @@ public:
   }
 
   template <typename Type, typename ParentType>
-  utils::result<void, utils::error> attach(const std::string name) {
+  [[nodiscard]] utils::result<void, utils::error> attach(const std::string name) {
     auto node = schema_node::make_node<Type>(*this, name);
 
     auto result = attach_node(node, std::type_index(typeid(ParentType)));

include/matador/utils/result.hpp

@@ -156,7 +156,7 @@ public:
   [[nodiscard]] bool is_ok() const { return !result_.has_value(); }
   [[nodiscard]] bool is_error() const { return result_.has_value(); }
 
-  ErrorType&& release_error() { return result_->release(); }
+  ErrorType&& release_error() { return std::move(*result_); }
 
   const ErrorType& err() const { return result_.value(); }
   ErrorType err() { return result_.value(); }
@@ -167,7 +167,7 @@ public:
       return result<SecondValueType, ErrorType>(ok(f()));
     }
 
-    return result<SecondValueType, ErrorType>(error(release_error()));
+    return result<SecondValueType, ErrorType>(failure(release_error()));
   }
 
   template<typename Func>
@@ -176,7 +176,7 @@ public:
       return f();
     }
 
-    return result(error(release_error()));
+    return result(failure(release_error()));
   }
 
   template<typename Func, typename SecondErrorType = typename std::invoke_result_t<Func, ErrorType >::value_type>