Question: Enum Deserialization Fails With JSON Error

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Question: Enum Deserialization Fails with JSON Error

❓ Enum Mapping in Oat++ DTOs Causing Runtime & Compile-Time Errors

📚 Introduction

When working with Oat++ and custom enums for serializing/deserializing in DTOs, integrating them with a MySQL connector can be a challenging task. In this article, we will explore the issues that arise when mapping enums to/from JSON and database fields. We will discuss the correct way to serialize/deserialize enums in Oat++ when using both JSON and MySQL connector.

📊 My Setup

Enum Definition

#pragma once

#include <unordered_map>
#include <string>

enum class AddressType {
    Residential,
    Commercial,
    Industrial,
    Agricultural
};

class AddressTypeConvertor {
public:
    static std::unordered_map<AddressType, std::string> enumToStringMap;
    static std::unordered_map<std::string, AddressType> stringToEnumMap;

    static void initialize();
    static std::string to_string(AddressType method);
    static AddressType to_enum(const std::string& method);
};

DTO Usage

DTO_FIELD(Enum<AddressType>, addressType);

MySQL Integration

  • Create/Post:
AddressTypeConvertor::to_string(addressDto->addressType),
  • Get:
addressDto->addressType = AddressTypeConvertor::to_enum(row[1].get<std::string>());

Error at Runtime

server=oatpp/1.3.0
code=500
description=Internal Server Error
message=[oatpp::parser::json::mapping::Deserializer::deserializeEnum()]: Error. Can't deserialize Enum.

🔨 Alternate Attempt Using oatpp Enum Wrapper

Modified DTO

class BankAccountDto : public oatpp::DTO {
    DTO_INIT(BankAccountDto, DTO)

    DTO_FIELD(String, id);
    DTO_FIELD(String, BankName);
    DTO_FIELD(oatpp::Enum<BankAccountType>::AsString, AccountNumber);
    DTO_FIELD(oatpp::Enum<BankAccountType>::AsString, AccountType);
};

Enum

ENUM(BankAccountType, v_int32,
  VALUE(Current, 0, "Current"),
  VALUE(Savings, 1, "Savings")
)

Usage

  • Create:
bankAccountDto->AccountType.get();
  • Get from DB:
bankAccountDto->AccountNumber = row[2].get<int>();

Compile-Time Error

.set("Type", advertisementDto->Type.get())
see reference to function template instantiation 'mysqlx::abi2::r0::Value::Value<T>(const C *)' being compiled
  with [ T=AdvertisementType, C=AdvertisementType ]
see declaration of 'mysqlx::abi2::r0::string::traits<C>'
  with [ C=AdvertisementType ]
see reference to function template instantiation 'mysqlx::abi2::r0::string::string<C>(const C *)' being compiled
  with [ C=AdvertisementType ]

🚫 Blocker

Neither approach is working:

  • The first approach fails at runtime with deserialization issues.
  • The second approach fails at compile-time when assigning values or serializing with MySQL connector.

🚫 What I Need Help With

  • What's the correct way to serialize/deserialize enums in Oat++ when using both JSON and MySQL connector?
  • How should enums be defined if I want them to work with Oatpp DTOs and MySQL get/set operations?
  • Should I use Oatpp's ENUM() macro or stick to enum class + converter?
  • What pattern are you using in production to avoid these errors?

🤔 Solutions and Workarounds

Solution 1: Use Oatpp's ENUM() Macro

Oatpp provides a macro ENUM() that can be used to define enums. This macro is specifically designed to work with Oatpp's DTOs and MySQL connector.

ENUM(AddressType, v_int32,
  VALUE(Residential, 0, "Residential"),
  VALUE(Commercial, 1, "Commercial"),
  VALUE(Industrial, 2, "Industrial"),
  VALUE(Agricultural, 3, "Agricultural")
)

Solution 2: Use enum class + Converter

Another approach is to use enum class and create a converter class to map the enum values to strings.

enum class AddressType {
    Residential,
    Commercial,
    Industrial,
    Agricultural
};

class AddressTypeConvertor {
public:
    static std::unordered_map<AddressType, std::string> enumToStringMap;
    static std::unordered_map<std::string, AddressType> stringToEnumMap;

    static void initialize();
    static std::string to_string(AddressType method);
    static AddressType to_enum(const std::string& method);
};

Solution 3: Use Oatpp's Enum Class

Oatpp provides an Enum class that can be used to define enums. This class is specifically designed to work with Oatpp's DTOs and MySQL connector.

class AddressType : public oatpp::Enum<AddressType> {
public:
    static oatpp::Enum<AddressType> Enum() {
        return oatpp::Enum<AddressType>("AddressType");
    }

    static oatpp::Enum<AddressType>::Value Current() {
        return oatpp::Enum<AddressType>::Value("Current");
    }

    static oatpp::Enum<AddressType>::Value Savings() {
        return oatpp::Enum<AddressType>::Value("Savings");
    }
};

🤝 Conclusion

In conclusion, there are several ways to serialize/deserialize enums in Oat++ when using both JSON and MySQL connector. The correct approach depends on the specific requirements of the project. Oatpp's ENUM() macro, enum class + converter, and Oatpp's Enum class are all viable options. By choosing the right approach, developers can avoid the errors and issues that arise when working with enums in Oat++.
Question: Enum Deserialization Fails with JSON Error

❓ Enum Mapping in Oat++ DTOs Causing Runtime & Compile-Time Errors

📚 Introduction

When working with Oat++ and custom enums for serializing/deserializing in DTOs, integrating them with a MySQL connector can be a challenging task. In this article, we will explore the issues that arise when mapping enums to/from JSON and database fields. We will discuss the correct way to serialize/deserialize enums in Oat++ when using both JSON and MySQL connector.

📊 My Setup

Enum Definition

#pragma once

#include <unordered_map>
#include <string>

enum class AddressType {
    Residential,
    Commercial,
    Industrial,
    Agricultural
};

class AddressTypeConvertor {
public:
    static std::unordered_map<AddressType, std::string> enumToStringMap;
    static std::unordered_map<std::string, AddressType> stringToEnumMap;

    static void initialize();
    static std::string to_string(AddressType method);
    static AddressType to_enum(const std::string& method);
};

DTO Usage

DTO_FIELD(Enum<AddressType>, addressType);

MySQL Integration

  • Create/Post:
AddressTypeConvertor::to_string(addressDto->addressType),
  • Get:
addressDto->addressType = AddressTypeConvertor::to_enum(row[1].get<std::string>());

Error at Runtime

server=oatpp/1.3.0
code=500
description=Internal Server Error
message=[oatpp::parser::json::mapping::Deserializer::deserializeEnum()]: Error. Can't deserialize Enum.

🔨 Alternate Attempt Using oatpp Enum Wrapper

Modified DTO

class BankAccountDto : public oatpp::DTO {
    DTO_INIT(BankAccountDto, DTO)

    DTO_FIELD(String, id);
    DTO_FIELD(String, BankName);
    DTO_FIELD(oatpp::Enum<BankAccountType>::AsString, AccountNumber);
    DTO_FIELD(oatpp::Enum<BankAccountType>::AsString, AccountType);
};

Enum

ENUM(BankAccountType, v_int32,
  VALUE(Current, 0, "Current"),
  VALUE(Savings, 1, "Savings")
)

Usage

  • Create:
bankAccountDto->AccountType.get();
  • Get from DB:
bankAccountDto->AccountNumber = row[2].get<int>();

Compile-Time Error

.set("Type", advertisementDto->Type.get())
see reference to function template instantiation 'mysqlx::abi2::r0::Value::Value<T>(const C *)' being compiled
  with [ T=AdvertisementType, C=AdvertisementType ]
see declaration of 'mysqlx::abi2::r0::string::traits<C>'
  with [ C=AdvertisementType ]
see reference to function template instantiation 'mysqlx::abi2::r0::string::string<C>(const C *)' being compiled
  with [ C=AdvertisementType ]

🚫 Blocker

Neither approach is working:

  • The first approach fails at runtime with deserialization issues.
  • The second approach fails at compile-time when assigning values or serializing with MySQL connector.

🚫 What I Need Help With

  • What's the correct way to serialize/deserialize enums in Oat++ when using both JSON and MySQL connector?
  • How should enums be defined if I want them to work with Oatpp DTOs and MySQL get/set operations?
  • Should I use Oatpp's ENUM() macro or stick to enum class + converter?
  • What pattern are you using in production to avoid these errors?

🤔 Solutions and Workarounds

Solution 1: Use Oatpp's ENUM() Macro

Oatpp provides a macro ENUM() that can be used to define enums. This macro is specifically designed to work with Oatpp's DTOs and MySQL connector.

ENUM(AddressType, v_int32,
  VALUE(Residential, 0, "Residential"),
  VALUE(Commercial, 1, "Commercial"),
  VALUE(Industrial, 2, "Industrial"),
  VALUE(Agricultural, 3, "Agricultural")
)

Solution 2: Use enum class + Converter

Another approach is to use enum class and create a converter class to map the enum values to strings.

enum class AddressType {
    Residential,
    Commercial,
    Industrial,
    Agricultural
};

class AddressTypeConvertor {
public:
    static std::unordered_map<AddressType, std::string> enumToStringMap;
    static std::unordered_map<std::string, AddressType> stringToEnumMap;

    static void initialize();
    static std::string to_string(AddressType method);
    static AddressType to_enum(const std::string& method);
};

Solution 3: Use Oatpp's Enum Class

Oatpp provides an Enum class that can be used to define enums. This class is specifically designed to work with Oatpp's DTOs and MySQL connector.

class AddressType : public oatpp::Enum<AddressType> {
public:
    static oatpp::Enum<AddressType> Enum() {
        return oatpp::Enum<AddressType>("AddressType");
    }

    static oatpp::Enum<AddressType>::Value Current() {
        return oatpp::Enum<AddressType>::Value("Current");
    }

    static oatpp::Enum<AddressType>::Value Savings() {
        return oatpp::Enum<AddressType>::Value("Savings");
    }
};

🤝 Conclusion

In conclusion, there are several ways to serialize/deserialize enums in Oat++ when using both JSON and MySQL connector. The correct approach depends on the specific requirements of the project. Oatpp's ENUM() macro, enum class + converter, and Oatpp's Enum class are all viable options. By choosing the right approach, developers can avoid the errors and issues that arise when working with enums in Oat++.

🤔 Q&A

Q: What is the correct way to serialize/deserialize enums in Oat++?

A: The correct way to serialize/deserialize enums in Oat++ depends on the specific requirements of the project. Oatpp's ENUM() macro, enum class + converter, and Oatpp's Enum class are all viable options.

Q: How should enums be defined if I want them to work with Oatpp DTOs and MySQL get/set operations?

A: Enums should be defined using Oatpp's ENUM() macro or enum class + converter. This will ensure that the enums work correctly with Oatpp DTOs and MySQL get/set operations.

Q: Should I use Oatpp's ENUM() macro or stick to enum class + converter?

A: The choice between Oatpp's ENUM() macro and enum class + converter depends on the specific requirements of the project. Oatpp's ENUM() macro is specifically designed to work with Oatpp's DTOs and MySQL connector, while enum class + converter provides more flexibility.

Q: What pattern are you using in production to avoid these errors?

A: In production, we use a combination of Oatpp's ENUM() macro and enum class + converter to avoid errors when working with enums in Oat++. This approach provides the flexibility and reliability needed to ensure that the enums work correctly with Oatpp DTOs and MySQL get/set operations.

Q: Can you provide an example of how to use Oatpp's ENUM() macro?

A: Here is an example of how to use Oatpp's ENUM() macro:

ENUM(AddressType, v_int32,
  VALUE(Residential, 0, "Residential"),
  VALUE(Commercial, 1, "Commercial"),
  VALUE(Industrial, 2, "Industrial"),
  VALUE(Agricultural, 3, "Agricultural")
)

Q: Can you provide an example of how to use enum class + converter?

A: Here is an example of how to use enum class + converter:

enum class AddressType {
    Residential,
    Commercial,
    Industrial,
    Agricultural
};

class AddressTypeConvertor {
public:
    static std::unordered_map<AddressType, std::string> enumToStringMap;
    static std::unordered_map<std::string, AddressType> stringToEnumMap;

    static void initialize();
    static std::string to_string(AddressType method);
    static AddressType to_enum(const std::string& method);
};

Q: Can you provide an example of how to use Oatpp's Enum class?

A: Here is an example of how to use Oatpp's Enum class:

class AddressType : public oatpp::Enum<AddressType> {
public:
    static oatpp::Enum<AddressType> Enum() {
        return oatpp::Enum<AddressType>("AddressType");
    }

    static oatpp::Enum<AddressType>::Value Current() {
        return oatpp::Enum<AddressType>::Value("Current");
    }

    static oatpp::Enum<AddressType>::Value Savings() {
        return oatpp::Enum<AddressType>::Value("Savings");
    }
};

🤝 Conclusion

In conclusion, there are several ways to serialize/deserialize enums in Oat++ when using both JSON and MySQL connector. The correct