---
title: Basic Serialization
sidebar_position: 2
id: basic_serialization
license: |
  Licensed to the Apache Software Foundation (ASF) under one or more
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  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
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     http://www.apache.org/licenses/LICENSE-2.0

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  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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---

This page covers basic object graph serialization and the core serialization APIs.

## Object Graph Serialization

Apache Fory™ provides automatic serialization of complex object graphs, preserving the structure and relationships between objects. The `FORY_STRUCT` macro generates efficient serialization code at compile time, eliminating runtime overhead.

**Key capabilities:**

- Nested struct serialization with arbitrary depth
- Collection types (vector, set, map)
- Optional fields with `std::optional<T>`
- Smart pointers (`std::shared_ptr`, `std::unique_ptr`)
- Automatic handling of primitive types and strings
- Efficient binary encoding with variable-length integers

```cpp
#include "fory/serialization/fory.h"
#include <vector>
#include <map>

using namespace fory::serialization;

// Define structs
struct Address {
  std::string street;
  std::string city;
  std::string country;

  bool operator==(const Address &other) const {
    return street == other.street && city == other.city &&
           country == other.country;
  }
};
FORY_STRUCT(Address, street, city, country);

struct Person {
  std::string name;
  int32_t age;
  Address address;
  std::vector<std::string> hobbies;
  std::map<std::string, std::string> metadata;

  bool operator==(const Person &other) const {
    return name == other.name && age == other.age &&
           address == other.address && hobbies == other.hobbies &&
           metadata == other.metadata;
  }
};
FORY_STRUCT(Person, name, age, address, hobbies, metadata);

int main() {
  auto fory = Fory::builder().xlang(true).build();
  fory.register_struct<Address>(100);
  fory.register_struct<Person>(200);

  Person person{
      "John Doe",
      30,
      {"123 Main St", "New York", "USA"},
      {"reading", "coding"},
      {{"role", "developer"}}
  };

  auto result = fory.serialize(person);
  auto decoded = fory.deserialize<Person>(result.value());
  assert(person == decoded.value());
}
```

## Serialization APIs

### Serialize to New Vector

```cpp
auto fory = Fory::builder().xlang(true).build();
fory.register_struct<MyStruct>(1);

MyStruct obj{/* ... */};

// Serialize - returns Result<std::vector<uint8_t>, Error>
auto result = fory.serialize(obj);
if (result.ok()) {
  std::vector<uint8_t> bytes = std::move(result).value();
  // Use bytes...
} else {
  // Handle error
  std::cerr << result.error().to_string() << std::endl;
}
```

### Serialize to Existing Buffer

```cpp
// Serialize to existing Buffer (fastest path)
Buffer buffer;
auto result = fory.serialize_to(buffer, obj);
if (result.ok()) {
  size_t bytes_written = result.value();
  // buffer now contains serialized data
}

// Serialize to existing vector (zero-copy)
std::vector<uint8_t> output;
auto result = fory.serialize_to(output, obj);
if (result.ok()) {
  size_t bytes_written = result.value();
  // output now contains serialized data
}
```

### Deserialize from Byte Array

```cpp
// Deserialize from raw pointer
auto result = fory.deserialize<MyStruct>(data_ptr, data_size);
if (result.ok()) {
  MyStruct obj = std::move(result).value();
}

// Deserialize from vector
std::vector<uint8_t> data = /* ... */;
auto result = fory.deserialize<MyStruct>(data);

// Deserialize from Buffer (updates reader_index)
Buffer buffer(data);
auto result = fory.deserialize<MyStruct>(buffer);
```

## Error Handling

Fory uses a `Result<T, Error>` type for error handling:

```cpp
auto result = fory.serialize(obj);

// Check if operation succeeded
if (result.ok()) {
  auto value = std::move(result).value();
  // Use value...
} else {
  Error error = result.error();
  std::cerr << "Error: " << error.to_string() << std::endl;
}

// Or use FORY_TRY macro for early return
FORY_TRY(bytes, fory.serialize(obj));
// Use bytes directly...
```

Common error types:

- `Error::type_mismatch` - Type ID mismatch during deserialization
- `Error::invalid_data` - Invalid or corrupted data
- `Error::buffer_out_of_bound` - Buffer overflow/underflow
- `Error::type_error` - Type registration error

## The FORY_STRUCT Macro

The `FORY_STRUCT` macro registers a class for serialization (struct works the
same way):

```cpp
class MyStruct {
public:
  int32_t x;
  std::string y;
  std::vector<int32_t> z;
  FORY_STRUCT(MyStruct, x, y, z);
};
```

Private fields are supported when the macro is placed in a `public:` section:

```cpp
class PrivateUser {
public:
  PrivateUser(int32_t id, std::string name) : id_(id), name_(std::move(name)) {}

  bool operator==(const PrivateUser &other) const {
    return id_ == other.id_ && name_ == other.name_;
  }

private:
  int32_t id_ = 0;
  std::string name_;

public:
  FORY_STRUCT(PrivateUser, id_, name_);
};
```

The macro:

1. Generates compile-time field metadata
2. Enables member or ADL (Argument-Dependent Lookup) discovery for serialization
3. Creates efficient serialization code via template specialization

**Requirements:**

- Must be declared inside the class definition (struct works the same way) or
  at namespace scope
- Must be placed after all field declarations (when used inside the class)
- When used inside a class, the macro must be placed in a `public:` section
- All listed fields must be serializable types
- Field order in the macro is not important

## External / Third-Party Types

When you cannot modify a third-party type, use `FORY_STRUCT` at namespace
scope. This only works with **public** fields.

```cpp
namespace thirdparty {
struct Foo {
  int32_t id;
  std::string name;
};

FORY_STRUCT(Foo, id, name);
} // namespace thirdparty
```

**Limitations:**

- Must be declared at namespace scope in the same namespace as the type
- Only public fields are supported

## Inherited Fields

To include base-class fields in a derived type, use `FORY_BASE(Base)` inside
`FORY_STRUCT`. The base must define its own `FORY_STRUCT` so its fields can be
referenced.

```cpp
struct Base {
  int32_t a;
  FORY_STRUCT(Base, a);
};

struct Derived : Base {
  int32_t b;
  FORY_STRUCT(Derived, FORY_BASE(Base), b);
};
```

**Notes:**

- Base fields are serialized before derived fields.
- Only fields visible from the derived type are supported.

## Nested Structs

Nested structs are fully supported:

```cpp
struct Inner {
  int32_t value;
  FORY_STRUCT(Inner, value);
};

struct Outer {
  Inner inner;
  std::string label;
  FORY_STRUCT(Outer, inner, label);
};

// Both must be registered
fory.register_struct<Inner>(1);
fory.register_struct<Outer>(2);
```

## Performance Tips

- **Buffer Reuse**: Use `serialize_to(buffer, obj)` with pre-allocated buffers
- **Pre-registration**: Register all types before serialization starts
- **Single-Threaded**: Use `build()` instead of `build_thread_safe()` when possible
- **Disable Tracking**: Use `track_ref(false)` when references aren't needed
- **Compact Encoding**: Variable-length encoding for space efficiency

## Related Topics

- [Configuration](configuration.md) - Builder options
- [Type Registration](type-registration.md) - Registering types
- [Supported Types](supported-types.md) - All supported types