[英]Scalaz validation with Argonaut
I have a case class and companion object: 我有一个案例类和同伴对象:
case class Person private(name: String, age: Int)
object Person {
def validAge(age: Int) = {
if (age > 18) age.successNel else "Age is under 18".failureNel
}
def validName(name: String) = {
name.successNel
}
def create(name: String, age: Int) = (validAge(age) |@| validName(name))(Person.apply)
}
I want to use Argonaut to parse some JSON and return a Person OR some errors, as a list. 我想使用Argonaut解析一些JSON并以列表形式返回Person或一些错误。 So I need to:
所以我需要:
I want to return errors in the form of something I can turn into some more JSON like: 我想以某种形式返回错误,我可以将其转换为更多的JSON,例如:
{
errors: ["Error1", "Error2"]
}
I first tried using Argonauts decodeValidation method, which returns a Validation[String, X]. 我首先尝试使用Argonauts的encodeValidation方法,该方法返回Validation [String,X]。 Unfortunately, I need a List of errors.
不幸的是,我需要一个错误列表。
Any suggestions? 有什么建议么?
I'm adding this as an answer because it's how I'd solve the problem off the top of my head, but I haven't been keeping up closely with Argonaut development for a while, and I'd love to hear that there's a better way. 我将其添加为答案,因为这是我从头开始解决问题的方法,但是一段时间以来我一直没有与Argonaut开发保持紧密联系,我很乐意听到有一个问题更好的方法。 First for the setup, which fixes a few little issues in yours, and adds a condition for validity on names to make the examples later more interesting:
首先进行设置,它可以解决您的一些小问题,并为名称添加有效条件,以使后面的示例更加有趣:
import scalaz._, Scalaz._
case class Person private(name: String, age: Int)
object Person {
def validAge(age: Int): ValidationNel[String, Int] =
if (age > 18) age.successNel else "Age is under 18".failureNel
def validName(name: String): ValidationNel[String, String] =
if (name.size >= 3) name.successNel else "Name too short".failureNel
def create(name: String, age: Int) =
(validName(name) |@| validAge(age))(Person.apply)
}
And then I'd decode the JSON into a (String, Int)
pair before creating the Person
: 然后在创建
Person
之前(String, Int)
将JSON解码为(String, Int)
对:
import argonaut._, Argonaut._
def decodePerson(in: String): ValidationNel[String, Person] =
Parse.decodeValidation(in)(
jdecode2L((a: String, b: Int) => (a, b)
)("name", "age")).toValidationNel.flatMap {
case (name, age) => Person.create(name, age)
}
And then: 接着:
scala> println(decodePerson("""{ "name": "", "age": 1 }"""))
Failure(NonEmptyList(Name too short, Age is under 18))
Note that this doesn't accumulate errors in more complex cases—eg if the value of the name
field is a number and age
is 1
, you'll only get a single error (the name
one). 请注意,这不会在更复杂的情况下累积错误-例如,如果
name
字段的值是数字并且age
是1
,那么您只会得到一个错误( name
one)。 Making error accumulation work in cases like that would be considerably more complex. 在这种情况下使错误累积有效得多。
Relatedly, you'll also see a deprecation warning about the flatMap
on Validation
, which you can think of as a reminder that accumulation won't happen across the bind. 相关地,您还会在
Validation
上看到关于flatMap
的弃用警告,可以将其视为提醒,不会在绑定期间发生累积。 You can tell the compiler that you understand by importing scalaz.Validation.FlatMap._
. 您可以通过导入
scalaz.Validation.FlatMap._
告诉编译器您了解。
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