Merge pull request #125 from heinezen/feature/parent_check

Handle casting from `ValueHolder` to specific `Value` directly in nyan API

Author: TheJJ

nyan/CMakeLists.txt

@@ -30,6 +30,7 @@ add_library(nyan SHARED
 	basic_type.cpp
 	c3.cpp
 	change_tracker.cpp
+	concept.cpp
 	config.cpp
 	curve.cpp
 	database.cpp

nyan/concept.cpp

@@ -0,0 +1,10 @@
+// Copyright 2025-2025 the nyan authors, LGPLv3+. See copying.md for legal info.
+
+#include "concept.h"
+
+
+namespace nyan {
+
+// this file is intentionally empty
+
+}

nyan/concept.h

@@ -0,0 +1,27 @@
+// Copyright 2025-2025 the nyan authors, LGPLv3+. See copying.md for legal info.
+
+#pragma once
+
+#include <concepts>
+
+
+namespace nyan {
+
+class Value;
+class Object;
+
+/**
+ * Type that is a nyan value.
+ */
+template <typename T>
+concept ValueLike = std::derived_from<T, Value>;
+
+/**
+ * Type that is either a nyan value or object.
+ * Object is not a value (ObjectValue is), but want to allow an
+ * overloaded conversion for direct object access.
+ */
+template <typename T>
+concept ValueOrObjectLike = std::is_same_v<T, Object> or ValueLike<T>;
+
+} // namespace nyan

nyan/object.cpp

@@ -1,4 +1,4 @@
-// Copyright 2016-2024 the nyan authors, LGPLv3+. See copying.md for legal info.
+// Copyright 2016-2025 the nyan authors, LGPLv3+. See copying.md for legal info.
 
 #include "object.h"
 
@@ -192,6 +192,10 @@ const std::deque<fqon_t> &Object::get_parents(order_t t) const {
 
 
 bool Object::has(const memberid_t &member, order_t t) const {
+	return this->has_member(member, t);
+}
+
+bool Object::has_member(const memberid_t &member, order_t t) const {
 	// TODO: cache?
 
 	const std::vector<fqon_t> &lin = this->get_linearized(t);
@@ -206,7 +210,7 @@ bool Object::has(const memberid_t &member, order_t t) const {
 }
 
 
-bool Object::extends(fqon_t other_fqon, order_t t) const {
+bool Object::extends(const fqon_t &other_fqon, order_t t) const {
 	if (this->name == other_fqon) {
 		return true;
 	}

nyan/object.h

@@ -1,8 +1,7 @@
-// Copyright 2016-2023 the nyan authors, LGPLv3+. See copying.md for legal info.
+// Copyright 2016-2025 the nyan authors, LGPLv3+. See copying.md for legal info.
 #pragma once
 
 
-#include <concepts>
 #include <deque>
 #include <memory>
 #include <sstream>
@@ -11,6 +10,7 @@
 #include <vector>
 
 #include "api_error.h"
+#include "concept.h"
 #include "config.h"
 #include "object_notifier_types.h"
 #include "util.h"
@@ -31,15 +31,6 @@ class Value;
 class View;
 
 
-/**
- * Type that is either a nyan value or object.
- * Object is not a value (ObjectValue is), but want to allow an
- * overloaded conversion for direct object access.
- */
-template <typename T>
-concept ValueLike = std::derived_from<T, Value> || std::is_same_v<T, Object>;
-
-
 /**
  * Handle for accessing a nyan object independent of time.
  */
@@ -105,7 +96,7 @@ class Object {
 	 *
 	 * @return Value of the member.
 	 */
-	template <ValueLike T>
+	template <ValueOrObjectLike T>
 	std::shared_ptr<T> get(const memberid_t &member, order_t t = LATEST_T) const;
 
 	/**
@@ -119,7 +110,7 @@ class Object {
 	 *
 	 * @return Value of the member.
 	 */
-	template <ValueLike T, bool may_be_none = true>
+	template <ValueOrObjectLike T, bool may_be_none = true>
 	std::optional<std::shared_ptr<T>> get_optional(const memberid_t &member, order_t t = LATEST_T) const;
 
 	/**
@@ -245,19 +236,30 @@ class Object {
 	 *
 	 * @return true if the member exists for this object, else false.
 	 */
+	[[deprecated("Use has_member(..) instead")]]
 	bool has(const memberid_t &member, order_t t = LATEST_T) const;
 
 	/**
-	 * Check if this object is a child of the given parent at a given time.
+	 * Check if this object has a member with a given name at a given time.
+	 *
+	 * @param member Identifier of the member.
+	 * @param t Time for which the member existence is checked.
+	 *
+	 * @return true if the member exists for this object, else false.
+	 */
+	bool has_member(const memberid_t &member, order_t t = LATEST_T) const;
+
+	/**
+	 * Check if this object is a descendant/child of the given object at a given time.
 	 *
-	 * @param other_fqon Identifier of the suspected parent object.
+	 * @param other_fqon Identifier of the suspected parent/ancestor object.
 	 * @param t Time for which the relationship is checked.
 	 *
-	 * @return true if the parent's identifier equals this object's
-	 *     identifier or that of any of its (transitive) parents,
-	 *     else false
+	 * @return true if the ancestors's identifier equals this object's
+	 *         identifier or that of any of its (transitive) parents,
+	 *         else false
 	 */
-	bool extends(fqon_t other_fqon, order_t t = LATEST_T) const;
+	bool extends(const fqon_t &other_fqon, order_t t = LATEST_T) const;
 
 	/**
 	 * Get the metadata information object for this object.
@@ -335,14 +337,14 @@ class Object {
 };
 
 
-template <ValueLike T>
+template <ValueOrObjectLike T>
 std::shared_ptr<T> Object::get(const memberid_t &member, order_t t) const {
 	auto ret = this->get_optional<T, false>(member, t);
 	return *ret;
 }
 
 
-template <ValueLike T, bool may_be_none>
+template <ValueOrObjectLike T, bool may_be_none>
 std::optional<std::shared_ptr<T>> Object::get_optional(const memberid_t &member, order_t t) const {
 	std::shared_ptr<Value> value = this->get_value(member, t).get_ptr();
 	if constexpr (may_be_none) {

nyan/value/value_holder.h

@@ -1,8 +1,12 @@
-// Copyright 2017-2021 the nyan authors, LGPLv3+. See copying.md for legal info.
+// Copyright 2017-2025 the nyan authors, LGPLv3+. See copying.md for legal info.
 #pragma once
 
 #include <memory>
 
+#include "../api_error.h"
+#include "../concept.h"
+#include "../util.h"
+
 
 namespace nyan {
 
@@ -26,12 +30,26 @@ class ValueHolder {
 	ValueHolder &operator=(const std::shared_ptr<Value> &value);
 
 	/**
-	 * Get the shared pointer of this ValueHolder.
+	 * Get the shared pointer to the value wrapped by this holder.
 	 *
 	 * @return Shared pointer to this holder's value.
 	 */
 	const std::shared_ptr<Value> &get_ptr() const;
 
+	/**
+	 * Get a shared pointer to the value stored by this holder.
+	 *
+	 * Auto-converts the value to type T, which must be a nyan::Value type.
+	 *
+	 * @tparam T Type of the value to retrieve.
+	 *
+	 * @return Value stored by this holder.
+	 *
+	 * @throws InternalError if the value is not of type T.
+	 */
+	template <ValueLike T>
+	const std::shared_ptr<T> get_value_ptr() const;
+
 	/**
 	 * Check if this holder points to a value.
 	 *
@@ -74,6 +92,20 @@ class ValueHolder {
 	std::shared_ptr<Value> value;
 };
 
+
+template <ValueLike T>
+const std::shared_ptr<T> ValueHolder::get_value_ptr() const {
+	auto ret = std::dynamic_pointer_cast<T>(this->value);
+
+	if (not ret) {
+		throw APIError{"ValueHolder does not contain a value of type "
+		               + util::typestring<T>() + ", but got "
+		               + util::typestring(this->value.get())};
+	}
+
+	return ret;
+}
+
 } // namespace nyan