如何为具有超过22个字段的案例类编写隐式Writes [英] How to write implicit Writes for case class having more than 22 fields

问题描述

case class Foo(
  _1:Int,_2:Int,_3:Int,_4:Int,_5:Int,
  _21:Int,_22:Int,_23:Int,_24:Int,_25:Int,
  _31:Int,_32:Int,_33:Int,_34:Int,_35:Int,
  _41:Int,_42:Int,_43:Int,_44:Int,_45:Int,
  _51:Int,_52:Int,_53:Int,_54:Int,_55:Int
)

对于这样的案例类，我需要编写隐式的json de/序列化器. 我尝试拆分字段，并使用JSONFormat.但是我仍然需要使用Json.obj()的隐式OWrited.我也尝试过play-json-extensions.有什么想法吗?

For a case class like this, I need to write implicit json de- / serializer. I tried splitting the fields, and had a JSONFormat. But still I need implicit OWrited for using Json.obj(). I tried with play-json-extensions also. Any ideas?

推荐答案

这里确实有3种途径可供您探索:

There's really 3 avenues for you to explore here:

1. 自己明确地写出每个班级(是的，大量的样板.)
2. 使用Macros或 Shapeless 完成.
3. 使用已经做过#2的某人的图书馆.

1. Write out each class explicitly yourself (yes, tons of boilerplate.)
2. Do it with Macros or Shapeless.
3. Use someone's library who already did #2.

当别人为我工作时，我喜欢它.因此，考虑到这一点，#3似乎是我的首选解决方案...您会知道什么?有人这样做了: play-json-derived-codecs .由于它使用 Shapeless ，它将能够处理任意大小的案例类，而不仅限于那些受大小限制的案例类. ProductN(1-22，具体取决于您的Scala版本.)

I like it when someone else does the work for me. So with that in mind, #3 seems like my preferred solution... And what would you know? Someone else did just that: play-json-derived-codecs. Since it uses Shapeless, it will be able to handle case classses of arbitrary size, not just those constrained by ProductN (1-22, depending on your version of Scala.)

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