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Just published an article about
"How to use Arrows Either for exception handling in your application" <https://medium.com/@inzuael/how-to-use-arrows-either-for-exception-handling-in-your-application-a73574b39d07|https://medium.com/@inzuael/how-to-use-arrows-either-for-exception-handling-in-your-application-a73574b39d07>

Hey! The article is quite good.

We're building a library to make this easier: <https://github.com/arrow-kt/arrow-exact|https://github.com/arrow-kt/arrow-exact>. It's still experimental, but I think it's promising :)

Also, you can use `bind` instead of `flatMap`in a lot of cases to simplify the code. For example, these two snippets do exactly the same thing:

```fun addNewUser(user: UserDto): Either&lt;Failure, User&gt; {
    return user.toUser().flatMap {
        userRepository.save(it)
    }
}
```
```fun addNewUser(user: UserDto) = either {
    userRepository.save(
        user.toUser().bind()
    )
}
```
In this small example, the difference is slight, but it allows to avoid the nested lambda, thus reducing indentation. It also composes much better.

Thanks for your valuable feedback. I just started with Either few weeks ago and I'm still in the exploration phase. There is a lot possible and I need to find the best working ways. 
I will have a look on your suggestions

Do have the correct return type I need to call bind() twice
```    override fun addNewUser(user: UserDto): Either&lt;Failure, User&gt; = either {
        userRepository.save(user.toUser().bind()).bind()
    }```

The `arrow-exact` library gives me the posibility to create value classes that are returning an `Exact` result type depending of valid/invalid input. Out of this I can compose more complex objects. This solves the problem of validation depends on single properites.
But for me the problem remains that I maybe have validations which include multiple properties. So for this I still need a workaround in case I want to use a data class. In this case with `Exact` I also need to use an object type containing multiple properties as raw input.
Something like:
```data class TopicDto(
    val id: Identity,
    val name: String,
    val category: String
)

data class Topic(
    val id: Identity,
    val name: String,
    val category: String,
) {
    companion object : Exact&lt;TopicDto, Topic&gt; {
        override fun Raise&lt;ExactError&gt;.spec(raw: TopicDto): Topic {
            ensure(raw.name.isNotEmpty())
            ensure(raw.category.length &gt; 5)
            return Topic(
                id = raw.id,
                name = raw.name,
                category = raw.category
            )
        }

    }
}```


Ah, that's true. Can you create an issue so we can discuss this with the others?

For what case do you mean? Using exact a data class having multiple properties (without definition of an extra typ for it)?

Yeah, that would be an interesting feature. I wonder if the solution would be to create an Exact instance for each field and compose them

Okay, I will try to explain my requirement.