Scala中案例类字段的最大数量是多少? [英] What is the maximum number of case class fields in scala?

问题描述

以前是22岁，听说有人说现在是512岁?那是对的吗?有人可以提供来源.

It used to be 22, I heard someone say it's now 512? Is that correct? Can someone provide a source.

推荐答案

在Scala 2.11中存在一个隐式限制，似乎如果创建一个包含大约100个以上字段的case类，则会出现堆栈溢出(请参阅答案底部) ).

In Scala 2.11 there is an implicit limit, it seems if you create a case class with about more than 100 fields you get a stack overflow (see bottom of answer).

一种用于提高字段数量(最多254个)的解决方法是

A workaround to get the number of fields higher (up to 254) is

export SBT_OPTS="-XX:MaxPermSize=2G -Xmx2G -Xms2G -Xss8M"

如果尝试高于254，您将得到

If you try any higher than 254 you get

[error] /Users/sams/src/.../src/main/scala/com/MegaClass.scala:6:12: Platform restriction: a parameter list's length cannot exceed 254.
[error] case class MegaClass(

堆栈溢出错误:

[error] null
[error] scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.transformSelect$1(SuperAccessors.scala:253)
[error] scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.transform(SuperAccessors.scala:335)
[error] scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.transform(SuperAccessors.scala:359)
[error] scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.transform(SuperAccessors.scala:71)
...
[error] scala.reflect.internal.Trees$class.itransform(Trees.scala:1345)
[error] scala.reflect.internal.SymbolTable.itransform(SymbolTable.scala:16)
[error] scala.reflect.internal.SymbolTable.itransform(SymbolTable.scala:16)
[error] scala.reflect.api.Trees$Transformer.transform(Trees.scala:2555)
[error] scala.tools.nsc.transform.TypingTransformers$TypingTransformer.transform(TypingTransformers.scala:44)
[error] scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.mayNeedProtectedAccessor$1(SuperAccessors.scala:186)
[error] scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.transformSelect$1(SuperAccessors.scala:332)
[error] scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.transform(SuperAccessors.scala:335)
[error] scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.transform(SuperAccessors.scala:359)
[error] scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.transform(SuperAccessors.scala:71)
[error] scala.reflect.internal.Trees$class.itransform(Trees.scala:1345)
[error]            
[error] java.lang.StackOverflowError
[error]     at scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.transform(SuperAccessors.scala:178)
[error]     at scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.transform(SuperAccessors.scala:359)
[error]     at scala.tools.nsc.typechecker.SuperAccessors$SuperAccTransformer.transform(SuperAccessors.scala:71)
[error]     at scala.reflect.internal.Trees$class.itransform(Trees.scala:1345)
[error]     at scala.reflect.internal.SymbolTable.itransform(SymbolTable.scala:16)
[error]     at scala.reflect.internal.SymbolTable.itransform(SymbolTable.scala:16)
[error]     at scala.reflect.api.Trees$Transformer.transform(Trees.scala:2555)

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