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IOLocal.scala
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IOLocal.scala
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/*
* Copyright 2020-2022 Typelevel
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package cats.effect
sealed trait IOLocal[A] {
def get: IO[A]
def set(value: A): IO[Unit]
def reset: IO[Unit]
def update(f: A => A): IO[Unit]
def modify[B](f: A => (A, B)): IO[B]
def getAndSet(value: A): IO[A]
def getAndReset: IO[A]
}
object IOLocal {
def apply[A](default: A): IO[IOLocal[A]] =
IO {
new IOLocal[A] { self =>
override def get: IO[A] =
IO.Local(state => (state, state.get(self).map(_.asInstanceOf[A]).getOrElse(default)))
override def set(value: A): IO[Unit] =
IO.Local(state => (state + (self -> value), ()))
override def reset: IO[Unit] =
IO.Local(state => (state - self, ()))
override def update(f: A => A): IO[Unit] =
get.flatMap(a => set(f(a)))
override def modify[B](f: A => (A, B)): IO[B] =
get.flatMap { a =>
val (a2, b) = f(a)
set(a2).as(b)
}
override def getAndSet(value: A): IO[A] =
get <* set(value)
override def getAndReset: IO[A] =
get <* reset
}
}
}