最近在学习 RAILS，发现大家会用到 SERALIZERS。查看官方文档有 ActiveModel::Serialization 已实现 as_json, serailizer_hash 这些功能，也有类似的 GEM 模块，有人指点下为什么需要用到序列化的外部模块吗？

jsonapi-rb is a highly performant and modular JSON:API-only implementation. There's a vibrant community around it that has produced projects such as JSON:API Suite.
fast_jsonapi is a lightning fast JSON:API serializer for Ruby Objects.
jsonapi-resources is a popular resource-focused framework for implementing JSON:API servers.
blueprinter is a fast, declarative, and API spec agnostic serializer that uses composable views to reduce duplication. From your friends at Procore.