---

title: Shared and Circular References sidebar_position: 6 id: references license: | Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

 http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Swift reference tracking is controlled by ForyConfig.trackRef.

Enable Reference Tracking

let fory = Fory(xlang: true, trackRef: true, compatible: false)

When enabled, reference-trackable types preserve identity and cycles.

Shared Reference Example

import Fory

@ForyObject
final class Animal {
    var name: String = ""

    required init() {}

    init(name: String) {
        self.name = name
    }
}

@ForyObject
final class AnimalPair {
    var first: Animal? = nil
    var second: Animal? = nil

    required init() {}

    init(first: Animal? = nil, second: Animal? = nil) {
        self.first = first
        self.second = second
    }
}

let fory = Fory(xlang: true, trackRef: true)
fory.register(Animal.self, id: 200)
fory.register(AnimalPair.self, id: 201)

let shared = Animal(name: "cat")
let input = AnimalPair(first: shared, second: shared)

let data = try fory.serialize(input)
let decoded: AnimalPair = try fory.deserialize(data)

assert(decoded.first === decoded.second)

Circular Reference Example (Use weak)

trackRef preserves the reference graph, but it does not change ARC ownership. Use weak on at least one edge in a cycle to avoid leaks.

import Fory

@ForyObject
final class Node {
    var value: Int32 = 0
    weak var next: Node? = nil

    required init() {}

    init(value: Int32, next: Node? = nil) {
        self.value = value
        self.next = next
    }
}

let fory = Fory(xlang: true, trackRef: true)
fory.register(Node.self, id: 300)

let node = Node(value: 7)
node.next = node

let data = try fory.serialize(node)
let decoded: Node = try fory.deserialize(data)

assert(decoded.next === decoded)

Notes

• Value types (struct, primitive values) do not carry identity semantics
• trackRef controls serialization graph identity, not ARC memory ownership
• Use trackRef=false for purely value-based payloads to reduce overhead