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package cc.spray.json
package lenses
/**
* The read lens can extract child values out of a JsValue hierarchy. A read lens
* is parameterized with a type constructor. This allows to extracts not only scalar
* values but also sequences or optional values.
* @tparam M
*/
trait ReadLens[M[_]] {
/**
* Given a parent JsValue, tries to extract the child value.
* @return `Right(value)` if the projection succeeds. `Left(error)` if the projection
* fails.
*/
def retr: JsValue => Validated[M[JsValue]]
/**
* Given a parent JsValue extracts and tries to convert the JsValue into
* a value of type `T`
*/
def tryGet[T: Reader](value: JsValue): Validated[M[T]]
/**
* Given a parent JsValue extracts and converts a JsValue into a value of
* type `T` or throws an exception.
*/
def get[T: Reader](value: JsValue): M[T]
/**
* Lifts a predicate for a converted value for this lens up to the
* parent level.
*/
def is[U: Reader](f: U => Boolean): JsPred
}
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