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Comment by cabalamat | Hacker News Reader

In the readme you say:

>This contrasts against traditional ("stateful") ORMs which use query builders (rather than raw SQL) to return database-aware (rather than pure) objects.

>The name pureORM reflects both that it is pure ORM (there is no query builder dimension) as well as the purity of the mapped Objects.

I don't know what you mean by "pure" or "purity" here, and i think an explantion would help.

Also, in the code:

    db.one(query)

"one" does not strike me as a particularly expressive method name.

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"single" might be a better name. The Kotlin standard library uses that name for a variant of the "filter" method (on collections) that returns a single matching element or throws an exception if there are more or fewer.

I thought it was first or firstOrNull. Or is there a new Kotlin collection method I need to learn about?

Aside, Kotlin collection extensions might be my favorite thing I learned in the last two years.

They are similar but slightly different. "single" checks that there is exactly one matching element:

  >>> listOf(1, 2, 3).single { it > 2 }
  res0: kotlin.Int = 3

  >>> listOf(1, 2, 3).single { it > 1 }
  java.lang.IllegalArgumentException: Collection contains more than one matching element.

  >>> listOf(1, 2, 3).single { it > 100 }
  java.util.NoSuchElementException: Collection contains no element matching the predicate.

Whereas "firstOrNull" returns the first result even if there are more, or null if there are none:

  >>> listOf(1, 2, 3).firstOrNull { it > 2 }
  res0: kotlin.Int? = 3

  >>> listOf(1, 2, 3).firstOrNull { it > 1 }
  res1: kotlin.Int? = 2

  >>> listOf(1, 2, 3).firstOrNull { it > 100 }
  res2: kotlin.Int? = null

Python's "next" function kind of acts like "single", except that it doesn't check that there aren't more than one matching element. I wish the itertools module had a function that did this.

I'm not familiar with it, but at first glance, "one()" stands in contrast to "multiple()". Either running a single query or running multiple queries in a request.

It is used for the amount of objects returned (not the amount of raw rows returned, to be clear). Many orms have `findOne` or `findAll` methods that return an object or an array respectively. Just helps to make things more ergonomic and usually appends a LIMIT clause.

Thanks for the correction. I guess that validates the OP's point after all.

Ah, that makes more sense now.

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