null-validator-annotation

Annotate your class, and it will generate null-validation code for that class. Useful for doing a validation layer over your input.

Assume you have the following data class that represents a User:

data class User {
  val id: String,
  val username: String,
  val email: String,
  val optionalData: String?
}

And you have a JSON string input that represents a User, but it's partial:

{
  "id": "123456",
  "username": "yolo123"
}

When this JSON is converted to the data class, the optionalData field is NULL which is OK, but the email field is also NULL even though it's non-nullable.

Eventually you'll end up writing a validation layer:

data class User {
  ...
  fun validate() {
    return id != null && username != null && email != null
  }
}

This is where the null-validator-annotation comes handy - it generates the validate() function as an extension function for your class.

For the following code:

@NullValidatorClass
data class User {
  val id: String,
  val username: String,
  val email: String,
  val optionalData: String?
}

The following code will be generated:

fun User.validate(): Boolean {
  val result = id != null && username != null && email != null && optionalData != null
  return result
}

And if you want to validate only some of the fields:

@NullValidatorClass
data class User {
  @NullValidatorField val id: String,
  @NullValidatorField val username: String,
  @NullValidatorField val email: String,
  val optionalData: String?
}

Then the following code will be generated:

fun User.validate(): Boolean {
  val result = id != null && username != null && email != null
  return result
}