Are there any advantages using maps instead of records to hold state in Erlang processes?

Question

Most of the books or online resources I've seen are all using records to hold the state of a process (probably because that was the way for more(?) than a decade). On the other hand, maps are effectively used to replace tuples in stdlib (for example childspecs in the supervisor module).

As an example, I am working my way through Learn You Some Erlang's Finite State Machines chapter and the state record could be replaced with a map, declared in the init/1 callback needed by gen_fsm.

• The record declaration won't be needed and most of what I've read so far, a best practice is to keep them local anyway as .hrl files make it harder to track errors.
• Referring to the process state in function clauses would also be shorter but they both clearly convey the structure of the state variable and a couple extra characters are not a concern.

Also, would it be more efficient?
I know that a well-thought out benchmark would answer my question but I am only a couple weeks into learning Erlang and the maps module is fairly new and still changing.

UPDATE: Thanks to I GIVE TERRIBLE ADVICE, I read the LYSE chapter on maps more thoroughly and the answer is clear:

Using records has the advantage that the keys are known at compile time that brings advantages of

• fast access to specific values (faster than what is possible dynamically)
• additional safety (crash early rather than corrupting state)
• easier type checking

These make records absolutely appropriate for a process' internal state, despite the occasional burden of writing a more verbose code_change function.

On the other hand, where Erlang users would use records to represent complex nested key/value data structures (oddly similar to objects in object-oriented languages) that would frequently cross module boundaries, maps will help a lot. Records were the wrong tool for that job.

Answer 1

我已经在了解你一些Erlang 网站上添加了一章专门介绍地图：http://learnyousomeerlang.com/maps

Mexican Standoff 部分专门将地图与记录和词组进行比较。从语义上讲，地图与记录更相似，而我的建议实际上是使用记录有意义的记录（具有O（1）访问权限的已知类型的受限密钥集），以及您拥有的地图使用dicts（异构的，灵活的键/值对集合）。

Answer 2

作为Joe Armstrong said：

  

记录已经死了 - 长期实时地图！

和

  

我们一直在讨论地图超过12年，但现在它们已经存在   留下来。

     

为什么漫长的等待？ - 我们希望地图能够替代记录   并且要像记录一样高效，而且它的表现并不明显   这样做。

所以，看起来地图还可以，我们已经将项目从记录切换到地图，我们感觉不到任何性能损失。

一个限制： 如果我是对的，你不能在mnesia中存储地图，因为你可以用记录来存储。