Validation
Ands this Validation with another, passed, Validation.
Ands this Validation with another, passed, Validation.
The result of and-ing two Validations is:
| Expression | Result |
|---|---|
Pass && Pass | Pass |
Pass && Fail(right) | Fail(right) |
Fail(left) && Pass | Fail(left) |
Fail(left) && Fail(right) | Fail(left) |
As you can see in the above table, no attempt is made by && to accumulate errors, which in turn means that
no constraint is placed on the E type (it need not be an Every). Instead, && short circuits
and returns the first Fail it encounters. This makes it useful in filters in for expressions involving Ors.
Here's an example:
import org.scalactic._ def isRound(i: Int): Validation[ErrorMessage] = if (i % 10 != 0) Fail(i + " was not a round number") else Pass def isDivBy3(i: Int): Validation[ErrorMessage] = if (i % 3 != 0) Fail(i + " was not divisible by 3") else Pass for (i <- Good(3) if isRound(i) && isDivBy3(i)) yield i // Result: Bad(3 was not a round number)
the other validation to and with this one
the result of anding this Validation with the other, passed, Validation
Represents the result of a validation, either the object
Passif the validation succeeded, else an instance ofFailcontaining an error value describing the validation failure.Validations are used to filterOrs inforexpressions orfiltermethod calls. For example, consider these methods:Because
isRoundandisDivBy3take anIntand return aValidation[ErrorMessage], you can use them in filters inforexpressions involvingOrs of typeIntOrErrorMessage. Here's an example:Validations can also be used to accumulate error usingwhen, a method that's made available by traitAccumulationon accumualtingOrs (Ors whoseBadtype is anEvery[T]). Here are some examples:Note: You can think of
Validationas an “Optionwith attitude,” wherePassis aNonethat indicates validation success andFailis aSomewhose value describes the validation failure.the type of error value describing a validation failure for this
Validation