Immutable entities via copyWithId setter

generator/lib/src/code_builder.dart

@@ -209,6 +209,7 @@ class CodeBuilder extends Builder {
     propInModel.name = prop.name;
     propInModel.type = prop.type;
     propInModel.flags = prop.flags;
+    propInModel.generatorFlags = prop.generatorFlags;
     propInModel.dartFieldType = prop.dartFieldType;
     propInModel.relationTarget = prop.relationTarget;
 

generator/lib/src/code_chunks.dart

@@ -130,7 +130,8 @@ class CodeChunks {
       id: ${createIdUid(property.id)},
       name: '${property.name}',
       type: ${property.type},
-      flags: ${property.flags}
+      flags: ${property.flags},
+      generatorFlags: ${property.generatorFlags}
       $additionalArgs
     )
     ''';
@@ -185,8 +186,12 @@ class CodeChunks {
   }
 
   static String setId(ModelEntity entity) {
+    if (entity.idProperty
+        .hasGeneratorFlag(OBXPropertyGeneratorFlags.USE_COPY_WITH_ID)) {
+      return '{return object.copyWithId(id);}';
+    }
     if (!entity.idProperty.fieldIsReadOnly) {
-      return '{object.${propertyFieldName(entity.idProperty)} = id;}';
+      return '{object.${propertyFieldName(entity.idProperty)} = id; return object;}';
     }
     // Note: this is a special case handling read-only IDs with assignable=true.
     // Such ID must already be set, i.e. it could not have been assigned.
@@ -198,6 +203,7 @@ class CodeChunks {
         "doesn't match the inserted ID (ID \$id). "
         'You must assign an ID before calling [box.put()].');
       }
+      return object;
     }''';
   }
 
@@ -399,6 +405,8 @@ class CodeChunks {
         if (entity.properties[index].isRelation) {
           if (paramDartType.startsWith('ToOne<')) {
             paramValueCode = 'ToOne(targetId: $paramValueCode)';
+          } else if (paramDartType.startsWith('ToOneProxy<')) {
+            paramValueCode = 'ToOneProxy(targetId: $paramValueCode)';
           } else if (paramType == 'optional-named') {
             log.info('Skipping constructor parameter $paramName on '
                 "'${entity.name}': the matching field is a relation but the type "
@@ -408,6 +416,8 @@ class CodeChunks {
         }
       } else if (paramDartType.startsWith('ToMany<')) {
         paramValueCode = 'ToMany()';
+      } else if (paramDartType.startsWith('ToManyProxy<')) {
+        paramValueCode = 'ToManyProxy()';
       } else {
         // If we can't find a positional param, we can't use the constructor at all.
         if (paramType == 'positional' || paramType == 'required-named') {
@@ -455,7 +465,7 @@ class CodeChunks {
       if (!p.isRelation) return;
       if (fieldReaders[index].isNotEmpty) {
         postLines.add(
-            'object.${propertyFieldName(p)}.targetId = ${fieldReaders[index]};');
+            'object.${propertyFieldName(p)}.relation.targetId = ${fieldReaders[index]};');
       }
       postLines.add('object.${propertyFieldName(p)}.attach(store);');
     });

generator/lib/src/entity_resolver.dart

@@ -116,14 +116,17 @@ class EntityResolver extends Builder {
 
       var isToManyRel = false;
       int? fieldType;
-      var flags = 0;
+      var flags = 0, generatorFlags = 0;
       int? propUid;
 
       _idChecker.runIfMatches(f, (annotation) {
         flags |= OBXPropertyFlags.ID;
         if (annotation.getField('assignable')!.toBoolValue()!) {
           flags |= OBXPropertyFlags.ID_SELF_ASSIGNABLE;
         }
+        if (annotation.getField('useCopyWith')!.toBoolValue()!) {
+          generatorFlags |= OBXPropertyGeneratorFlags.USE_COPY_WITH_ID;
+        }
       });
 
       _propertyChecker.runIfMatches(f, (annotation) {
@@ -210,6 +213,7 @@ class EntityResolver extends Builder {
         final prop = ModelProperty.create(
             IdUid(0, propUid ?? 0), f.name, fieldType,
             flags: flags,
+            generatorFlags: generatorFlags,
             entity: entity,
             uidRequest: propUid != null && propUid == 0);
 
@@ -242,7 +246,9 @@ class EntityResolver extends Builder {
     final idField = element.fields
         .singleWhere((FieldElement f) => f.name == entity.idProperty.name);
     if (idField.setter == null) {
-      if (!entity.idProperty.hasFlag(OBXPropertyFlags.ID_SELF_ASSIGNABLE)) {
+      if (!entity.idProperty.hasFlag(OBXPropertyFlags.ID_SELF_ASSIGNABLE) &&
+          !entity.idProperty
+              .hasGeneratorFlag(OBXPropertyGeneratorFlags.USE_COPY_WITH_ID)) {
         throw InvalidGenerationSourceError(
             "Entity ${entity.name} has an ID field '${idField.name}' that is "
             'not assignable (that usually means it is declared final). '
@@ -308,7 +314,7 @@ class EntityResolver extends Builder {
 
     final indexAnnotation = _indexChecker.firstAnnotationOfExact(f);
     final uniqueAnnotation = _uniqueChecker.firstAnnotationOfExact(f);
-    if (indexAnnotation == null && uniqueAnnotation == null) return null;
+    if (indexAnnotation == null && uniqueAnnotation == null) return;
 
     // Throw if property type does not support any index.
     if (fieldType == OBXPropertyType.Float ||
@@ -430,10 +436,11 @@ class EntityResolver extends Builder {
   bool isRelationField(FieldElement f) =>
       isToOneRelationField(f) || isToManyRelationField(f);
 
-  bool isToOneRelationField(FieldElement f) => f.type.element!.name == 'ToOne';
+  bool isToOneRelationField(FieldElement f) =>
+      const {'ToOne', 'ToOneProxy'}.contains(f.type.element!.name);
 
   bool isToManyRelationField(FieldElement f) =>
-      f.type.element!.name == 'ToMany';
+      const {'ToMany', 'ToManyProxy'}.contains(f.type.element!.name);
 
   bool isNullable(DartType type) =>
       type.nullabilitySuffix == NullabilitySuffix.star ||

objectbox/Makefile

@@ -11,7 +11,7 @@ help:			## Show this help
 all: depend test valgrind-test integration-test
 
 depend:			## Build dependencies
-	dart pub get
+	dart pub get 
 	../install.sh
 
 test: 			## Test all targets

objectbox/lib/objectbox.dart

@@ -24,8 +24,8 @@ export 'src/query.dart'
         QueryParamInt,
         QueryParamBool,
         QueryParamDouble;
-export 'src/relations/to_many.dart' show ToMany;
-export 'src/relations/to_one.dart' show ToOne;
+export 'src/relations/to_many.dart' show ToMany, ToManyProxy;
+export 'src/relations/to_one.dart' show ToOne, ToOneProxy;
 export 'src/store.dart' show Store, ObservableStore;
 export 'src/sync.dart'
     show

objectbox/lib/src/annotations.dart

@@ -134,8 +134,33 @@ class Id {
   /// telling which objects are new and which are already saved.
   final bool assignable;
 
+  /// Use copyWith new id in the entity identifier setter.
+  /// For example, if your entity is immutable object,
+  /// you can define useCopyWith as follows
+  ///
+  /// @Entity()
+  /// class ImmutableEntity {
+  ///   @Id(useCopyWith: true)
+  ///   final int? id;
+  ///
+  ///   final int payload;
+  ///
+  ///   ImmutableEntity copyWith({int? id, int? unique, int? payload}) =>
+  ///       ImmutableEntity(
+  ///         id: id,
+  ///         unique: unique ?? this.unique,
+  ///         payload: payload ?? this.payload,
+  ///       );
+  ///
+  ///   ImmutableEntity{this.id, required this.unique, required this.payload});
+  ///
+  ///   ImmutableEntity copyWithId(int newId) =>
+  ///       (id != newId) ? entity.copyWith(id: newId) : this;
+  /// }
+  final bool useCopyWith;
+
   /// Create an Id annotation.
-  const Id({this.assignable = false});
+  const Id({this.assignable = false, this.useCopyWith = false});
 }
 
 /// Transient annotation marks fields that should not be stored in the database.

objectbox/lib/src/modelinfo/entity_definition.dart

@@ -16,9 +16,9 @@ class EntityDefinition<T> {
   final int Function(T, fb.Builder) objectToFB;
   final T Function(Store, ByteData) objectFromFB;
   final int? Function(T) getId;
-  final void Function(T, int) setId;
-  final List<ToOne> Function(T) toOneRelations;
-  final Map<RelInfo, ToMany> Function(T) toManyRelations;
+  final T Function(T, int) setId;
+  final List<ToOneRelationProvider> Function(T) toOneRelations;
+  final Map<RelInfo, ToManyRelationProvider> Function(T) toManyRelations;
 
   const EntityDefinition(
       {required this.model,

objectbox/lib/src/modelinfo/enums.dart

@@ -138,6 +138,11 @@ abstract class OBXPropertyFlags {
   static const int UNIQUE_ON_CONFLICT_REPLACE = 32768;
 }
 
+abstract class OBXPropertyGeneratorFlags {
+  /// Use copyWithId in id setter
+  static const int USE_COPY_WITH_ID = 65536;
+}
+
 abstract class OBXPropertyType {
   /// < 1 byte
   static const int Bool = 1;

objectbox/lib/src/modelinfo/modelproperty.dart

@@ -10,7 +10,7 @@ class ModelProperty {
 
   late String _name;
 
-  late int _type, _flags;
+  late int _type, _flags, _generatorFlags;
   IdUid? _indexId;
   ModelEntity? entity;
   String? relationTarget;
@@ -51,6 +51,16 @@ class ModelProperty {
     _flags = value;
   }
 
+  int get generatorFlags => _generatorFlags;
+
+  set generatorFlags(int? value) {
+    if (value == null || value < 0) {
+      throw ArgumentError('generator flags must be defined and may not be < 0');
+    }
+
+    _generatorFlags = value;
+  }
+
   String get dartFieldType => _dartFieldType!;
 
   set dartFieldType(String value) => _dartFieldType = value;
@@ -92,6 +102,7 @@ class ModelProperty {
   // used in code generator
   ModelProperty.create(this.id, String? name, int? type,
       {int flags = 0,
+      int generatorFlags = 0,
       String? indexId,
       this.entity,
       String? dartFieldType,
@@ -101,6 +112,7 @@ class ModelProperty {
     this.name = name;
     this.type = type;
     this.flags = flags;
+    this.generatorFlags = generatorFlags;
     this.indexId = indexId == null ? null : IdUid.fromString(indexId);
   }
 
@@ -110,18 +122,21 @@ class ModelProperty {
       required String name,
       required int type,
       required int flags,
+      int? generatorFlags,
       IdUid? indexId,
       this.relationTarget})
       : _name = name,
         _type = type,
         _flags = flags,
+        _generatorFlags = generatorFlags ?? 0,
         _indexId = indexId,
         uidRequest = false;
 
   ModelProperty.fromMap(Map<String, dynamic> data, ModelEntity? entity)
       : this.create(IdUid.fromString(data['id'] as String?),
             data['name'] as String?, data['type'] as int?,
             flags: data['flags'] as int? ?? 0,
+            generatorFlags: data['generatorFlags'] as int? ?? 0,
             indexId: data['indexId'] as String?,
             entity: entity,
             dartFieldType: data['dartFieldType'] as String?,
@@ -134,6 +149,7 @@ class ModelProperty {
     ret['name'] = name;
     ret['type'] = type;
     if (flags != 0) ret['flags'] = flags;
+    if (generatorFlags != 0) ret['generatorFlags'] = generatorFlags;
     if (indexId != null) ret['indexId'] = indexId!.toString();
     if (relationTarget != null) ret['relationTarget'] = relationTarget;
     if (!forModelJson && _dartFieldType != null) {
@@ -144,6 +160,7 @@ class ModelProperty {
   }
 
   bool hasFlag(int flag) => (flags & flag) == flag;
+  bool hasGeneratorFlag(int flag) => (generatorFlags & flag) == flag;
 
   bool hasIndexFlag() =>
       hasFlag(OBXPropertyFlags.INDEXED) ||
@@ -167,6 +184,7 @@ class ModelProperty {
     result += ' type:${obxPropertyTypeToString(type)}';
     if (!isSigned) result += ' unsigned';
     result += ' flags:$flags';
+    result += ' generatorFlags:$generatorFlags';
 
     if (hasIndexFlag()) {
       result += ' index:' +