Custom fromSqlKey

[rpuey...@gmail.com]

Guys, how do I make a custom version of the 'fromSqlKey' function?

I'm using a 'uuid' as a key in the table and I wanted to convert an entity into the model. For this I did this function:

  fromEntity e = let value = entityVal e

                 in  CadastrosModel { id = fromSqlKey (entityKey  e)

                                 , email = cadastrosEmail value

                                 , cnpjCpf = cadastrosCnpjCpf value

                                 , password = cadastrosPassword value

                                 }

But fromSqlKey returns Int64. Is there any way to make uuid return?

The complete context is this:

[jsch...@gmail.com]

Why do you need the fromSqlKey at all? I use it almost only for debugging purpose.

Can you just write a new function?

fromSqlKey' :: Entity YourModel -> UUID

[rpuey...@gmail.com]

But that's where I got stuck. I have:

fromEntity e = ...

therefore 'e' is a Entity  record.

From the documentation I saw these two gets:

• entityKey :: Key record
   
• entityVal :: record

entityVal works. My record is a Cadastro according to the model:

Cadastros json

    Id UUID  sqltype=uuid   default=uuid_generate_v4()

    email Text

    cnpjCpf Text

    password Text

    deriving Typeable

There is still the question of how to get the value of the Key record

For those who are not key, I only have a record and then I can use, for example, cadastrosPassword. But what about the key?

[jsch...@gmail.com]

I read a few times but still don't really understand.

One important thing though: To my knowledge,

CadastrosId is an auto-generated alias for  Key Cadastros.

The id field is normally not in the model definition! It's auto-generated and it's always Int64 in Persistent.

So, to avoid name collissions, I strongly recommend to rename your custom Id field to e.g. id2.

You can add to your model definition:

  id2 UUID sqltype=uuid …

  UniqueId2 id2

The second line makes a unique index. Then you can use

getBy (UniqueId2 yourId)

To get your Id from an Entity, use this:

(cadastrosId2 . entityVal)

To get the real Int64 Persist Key, use entityKey

OK, the docs for Key rec say:

> By default, a backend will automatically generate the key Instead you can specify a Primary key made up of unique values.

- https://hackage.haskell.org/package/persistent-2.2.4/docs/Database-Persist-Class.html#t:Key

So this behavior might can be changed, but I'd stick to the default and can only recommend this article:

https://www.yesodweb.com/book/persistent

[jsch...@gmail.com]

I think I understand your question better now. I just stumbled upon the documentation "Custom ID column" at https://hackage.haskell.org/package/persistent-2.10.5.2/docs/Database-Persist-Quasi.html

fromSqlKey doesn't work because it returns Int64...

Don't you use the QuasiQuoter model definition for your Persist setup? In that case, have you used an upper-case i in the custom ID column definition?